Papers for Tuesday, Nov 01 2022

In space-based gravitational wave detection, the estimation of far-field wavefront error of the distorted beam is the precondition for the noise reduction. Zernike polynomials is used to describe the wavefront error of the transmitted distorted beam. The propagation of a laser beam between two telescope apertures is calculated numerically. Far-field wavefront error is estimated with the absolute height of the peak-to-valley phase deviation between distorted Gaussian beam and a reference distortion-free Gaussian beam. The results show the pointing jitter is strongly related to the wavefront error. Furthermore, when jitter decreases 10 times from 100 to 10 nrad, wavefront error reduces for more than an order of magnitude. In the analysis of multi-parameter minimization, the minimum of wavefront error tends to Z[5,3] Zernike in some parameter ranges. Some Zernikes have a strong correlation with wavefront error of the received beam. When the aperture diameter increases at Z[5,3] Zernike, wavefront error is not monotonic and has oscillation. Nevertheless, wavefront error almost remains constant with the arm length increasing from 10$^{-1}$ Mkm to 10$^3$ Mkm. When the arm length decreases for three orders of magnitude from 10$^{-1}$ Mkm to 10$^{-4}$ Mkm, wavefront error has only an order of magnitude increasing. In the range of 10$^{-4}$ Mkm to 10$^3$ Mkm, the lowest limit of the wavefront error is from 0.5 fm to 0.015 fm, at Z[5,3] Zernike and 10 nrad jitter.

Intermediate-Mass Black Holes (IMBHs), defined as having a mass in the range $10^3 \, \rm M_\odot$ to $10^6 \, \rm M_\odot$, are commonly found at the center of dwarf galaxies. Simulations and observations convincingly show that a sizable population of IMBHs could wander off-center in local galaxies. We use the cosmological simulation Astrid to study the orbital and radiative properties of wandering IMBHs in massive galaxies at $z \sim 3$. We find that this population of undetected black holes has large orbital inclinations ($60^\circ \pm 22^\circ$) with respect to the principal plane of the host. The eccentricity of their orbits is also significant ($0.6 \pm 0.2$) and decreases with time. Wandering IMBHs undergo spikes of accretion activity around the pericenter of their orbits, with rates $10^{-3}-10^{-5}$ times the Eddington rate and a median accretion duty cycle of $\sim 12 \%$. Their typical spectral energy distribution peaks in the infrared at $\sim 11 \, \mu \rm m$ rest frame. The studied IMBHs reach $2-10 \, \rm keV$ X-ray luminosities $> 10^{37} \, \mathrm{erg \, s^{-1}}$ for $\sim 10\%$ of the time. This luminosity corresponds to fluxes $>10^{-15} \, \mathrm{erg \, s^{-1} \, cm^{-2}}$ within $10$ Mpc. Two out of the 28 IMBHs studied ($\sim 7\%)$ have brief X-ray luminosity spikes $> 10^{41} \, \mathrm{erg \, s^{-1}}$, in the hyper-luminous X-ray sources (HLXs) regime. These findings suggest that HLXs are a small subset of the general wandering IMBH population, which is characterized by luminosities $10^3 - 10^4$ times fainter. Dedicated surveys with current and future observatories are needed to assess the demographics of this missing population of black holes.

Could new physics break the mirror symmetry of the Universe? Utilizing recent measurements of the parity-odd four-point correlation function of BOSS galaxies, we probe the physics of inflation by placing constraints on the amplitude of a number of parity-violating models. Within canonical models of (single-field, slow-roll) inflation, no parity-asymmetry can occur; however, it has recently been shown that breaking of the standard assumptions can lead to parity violation within the Effective Field Theory of Inflation (EFTI). In particular, we consider the Ghost Condensate and Cosmological Collider scenarios - the former for the leading and subleading operators in the EFTI and the latter for different values of mass and speed of an exchanged spin-$1$ particle - for a total of $18$ models. Each instance yields a definite prediction for the inflationary trispectrum, which we convert to a late-time galaxy correlator prediction (through a highly non-trivial calculation) and constrain using the observed data. We find no evidence for inflationary parity-violation (with each of the $18$ models having significances below $2.4\sigma$), and place the first constraints on the relevant coupling strengths, at a level comparable with the theoretical perturbativity bounds. This is also the first time Cosmological Collider signatures have directly been searched for in observational data. We further show that possible secondary parity-violating signatures in galaxy clustering can be systematically described within the Effective Field Theory of Large-Scale Structure. We argue that these late-time contributions are subdominant compared to the primordial parity-odd signal for a vast region of parameter space. In summary, the results of this paper disfavor the notion that the recent hints of parity-violation observed in the distribution of galaxies are due to new physics.

Castor is a system of six stars in which the two brighter objects, Castor A and B, revolve around each other every $\sim$450 yr and are both short-period spectroscopic binaries. They are attended by the more distant Castor C, which is also a binary. Here we report interferometric observations with the CHARA array that spatially resolve the companions in Castor A and B for the first time. We complement these observations with new radial velocity measurements of A and B spanning 30 yr, with the Hipparcos intermediate data, and with existing astrometric observations of the visual AB pair obtained over the past three centuries. We perform a joint orbital solution to solve simultaneously for the three-dimensional orbits of Castor A and B as well as the AB orbit. We find that they are far from being coplanar: the orbit of A is nearly at right angles (92 degrees) relative to the wide orbit, and that of B is inclined about 59 degrees compared to AB. We determine the dynamical masses of the four stars in Castor A and B to a precision better than 1%. We also determine the radii of the primary stars of both subsystems from their angular diameters measured with CHARA, and use them together with stellar evolution models to infer an age for the system of 290 Myr. The new knowledge of the orbits enables us to measure the slow motion of Castor C as well, which may assist future studies of the dynamical evolution of this remarkable sextuple system.

We present the results of a long-term periodicity search in a sample of $\gamma$-ray blazars within a multiwavelength context. These blazars have been selected from the Steward Observatory sample as part of its optical monitoring program between 2008 and 2018. We study 15 sources with a temporal coverage in their optical total and polarized emission sufficiently large ($>9$ years) to perform a reliable long-term periodicity analysis. We collect data from several observatories to extend the coverage, enabling the search of longer periods. In addition, data are also gathered in the high-energy ($E>100$ MeV) $\gamma$-ray band from the $\textit{Fermi}$ Large Area Telescope; and in the 15-GHz radio band from the Owens Valley Radio Observatory. We identify 5 promising candidates to host quasi-periodic emission, AO 0235+164, PKS 1222+216, Mrk 501, BL Lacertae and 1ES 2344+514 with periods in one or more bands and statistical significances $\sim$3$\sigma$ after trial factor correction. AO 0235+164 shows a period of $\sim$8.2 years in the R band; PKS 1222+216 has a quasi-periodic modulation in its total and polarized optical emission of $\sim$1.6 years; Mrk 501 displays a $\sim$5-year quasi-periodicity in optical and radio wavelengths; BL Lacertae presents a period of $\sim$1.8 years in its polarized emission; and 1ES 2344+514 shows a hint of a $\sim$5.5-year period in its optical R band. We interpret these results in the framework of the most common models and scenarios, namely the presence of a binary supermassive black hole system; or geometrical effects like helical or precessing jets.

Self-interacting dark matter (SIDM) offers the potential to mitigate some of the discrepancies between simulated cold dark matter (CDM) and observed galactic properties. We introduce a physically motivated SIDM model to understand the effects of self interactions on the properties of Milky Way and dwarf galaxy sized haloes. This model consists of dark matter with a nearly degenerate excited state, which allows for both elastic and inelastic scattering. In particular, the model includes a significant probability for particles to up-scatter from the ground state to the excited state. We simulate a suite of zoom-in Milky Way-sized N-body haloes with six models with different scattering cross sections to study the effects of up-scattering in SIDM models. We find that the up-scattering reaction greatly increases the central densities of the main halo through the loss of kinetic energy. However, the physical model still results in significant coring due to the presence of elastic scattering and down-scattering. These effects are not as apparent in the subhalo population compared to the main halo, but the number of subhaloes is reduced compared to CDM.

Using blazar light curves from the optical All-Sky Automated Survey for Supernovae (ASAS-SN) and the $\gamma$-ray \textit{Fermi}-LAT telescope, we performed the most extensive statistical correlation study between both bands, using a sample of 1,180 blazars. This is almost an order of magnitude larger than other recent studies. Blazars represent more than 98\% of the AGNs detected by \textit{Fermi}-LAT and are the brightest $\gamma$-ray sources in the extragalactic sky. They are essential for studying the physical properties of astrophysical jets from central black holes. However, their $\gamma$-ray flare mechanism is not fully understood. Multi-wavelength correlations help constrain the dominant mechanisms of blazar variability and the emission source region. For this purpose, we search for temporal relationships between optical and $\gamma$-ray bands. Using a Bayesian Block Decomposition, we detect 1414 optical and 510 $\gamma$-ray flares, we find a strong correlation between both bands. Among all the flares, we find 321 correlated flares from 133 blazars, and derive an average rest-frame time delay of only 1.1$_{-8.5}^{+7.1}$ days, with no difference between the flat-spectrum radio quasars, BL Lacertae-like objects or low, intermediate, and high-synchrotron peaked blazar classes. Our time-delay limit supports leptonic single-zone model as the driver for non-orphan flares. Limiting our search to well-defined light curves and removing 976 potential but unclear ``orphan'' flares, we find 191 (13\%) and 115 (22\%) clear ``orphan'' optical and $\gamma$-ray flares. The presence of ``orphan'' flares in both bands challenges the standard one-zone blazar flare leptonic model and suggests multi-zone synchrotron sites or a hadronic model for some blazars.

NGC 4472 is home to five ultraluminous X-ray sources hosted by globular clusters. These sources have been suggested as good black hole candidates in extragalactic globular clusters$-$ a highly sought after population that may provide observational information regarding the progenitors of merging black hole binaries. In this body of work, we present X-ray and optical follow up to one of these sources, CXOUJ1229410+075744 (GCU1). We find no evidence of [OIII] optical emission in GCU1 which indicates a lack of significant evidence for super-Eddington outflows, unlike what is seen in a handful of ULXs in extragalactic GCs. X-ray monitoring from 2019-2021 shows no detected X-ray emission above a few $\times$ $10^{38}$ erg/s. Comparisons of the multi-wavelength properties to disc-dominated, near Eddington Galactic black hole low mass X-ray binaries (GRS 1915+105 and XTEJ1817-330) suggests that GCU1 may show similar behaviour to GRS 1915+105 in terms of X-ray variability and similar relationships between $L_X$ and $kT$, with GCU1 showing maximum X-ray luminosities one order of magnitude higher.

Context. The ZOA does not allow clear optical observations of extragalactic sources behind the Milky Way due to the meaningful extinction of the optical emission of these objects. The observations in NIR wavelengths represent a potential source of astronomical discoveries supporting the detection of new galaxies, completing the picture of the large scale structure in this still little explored area of the sky. Aims. Our aim is to decipher the nature of the overdensity located behind the Milky Way, in the tile b204 of the VVV survey. Methods. We studied an area of six arcmin around a galaxy concentration located at l = 354.82{\deg} and b = -9.81{\deg}. We selected five galaxies taking into account the source distribution on the sky, in order to optimise the requested time for the observations, and we obtained the spectra with Flamingos 2 long-slit spectrograph at Gemini South 8.1-meter telescope. To identify and characterise the absorption features we have fitted the galaxies underlying spectrum using the starlight code together with the IRTF stellar library. In addition, the spectroscopic findings are reinforced using complementary photometric techniques such as red-sequence and photometric redshift estimation. Results. The mean spectroscopic redshift estimated from the NIR spectra is z = 0.225 +- 0.014. This value presents a good agreement with that obtained from photometric analysis, photoz = 0.21 +- 0.08, and the probability distribution function of the galaxies in the studied region. Also, the red-sequence slope is consistent with the one expected for NIR observations of galaxy clusters. Conclusions. The redshifts obtained from both, photometric and spectroscopic techniques are in good agreement allowing the confirmation of the nature of this structure at z = 0.225 +- 0.014, unveiling a new galaxy cluster, VVVGCl-B J181435-381432, behind the Milky Way bulge.

Shell galaxies make a class of tidally distorted galaxies, characterised by wide concentric arc(s), extending out to large galactocentric distances with sharp outer edges. Recent observations of young massive star clusters in the prominent outer shell of NGC 474 suggest that such systems host extreme conditions of star formation. In this paper, we present a hydrodynamic simulation of a galaxy merger and its transformation into a shell galaxy. We analyse how the star formation activity evolves with time, location-wise within the system, and what are the physical conditions for star formation. During the interaction, an excess of dense gas appears, triggering a starburst, i.e. an enhanced star formation rate and a reduced depletion time. Star formation coincides with regions of high molecular gas fraction, such as the galactic nucleus, spiral arms, and occasionally the tidal debris during the early stages of the merger. Tidal interactions scatter stars into a stellar spheroid, while the gas cools down and reforms a disc. The morphological transformation after coalescence stabilises the gas and thus quenches star formation, without the need for feedback from an active galactic nucleus. This evolution shows similarities with a compaction scenario for compact quenched spheroids at high-redshift, yet without a long red nugget phase. Shells appear after coalescence, during the quenched phase, implying that they do not host the conditions necessary for in situ star formation. The results suggest that shell-forming mergers might be part of the process of turning blue late-type galaxies into red and dead early-types.

We use here a family of scaling transformations, that scale key rates in the evolution equations, to analytically understand constraints on light relics from cosmic microwave background (CMB) maps, given cosmological models of varying degrees of complexity. We describe the causes of physical effects that are fundamentally important to the constraining power of the data, with a focus on the two that are most novel. We use as a reference model a cosmological model that admits a scaling transformation that increases light relic energy density while avoiding all of these causes. Constraints on light relics in a given model can then be understood as due to the differences between the given model and the reference model, as long as the additional light relics only interact gravitationally with the Standard Model components. This understanding supports the development of cosmological models that can evade light relics constraints from CMB maps.

The nitrogen chemical evolution during star and planet formation is still not fully understood. Ammonia (NH$_3$) is a key specie in the understanding of the molecular evolution in star-forming clouds and nitrogen isotope fractionation. In this paper, we present high spatial resolution observations of multiple emission lines of NH$_3$ toward the protobinary system NGC1333 IRAS4A with Karl G. Jansky Very Large Array (VLA). We spatially resolved the binary (hereafter 4A1 and 4A2) and detected compact emission of NH$_3$ transitions with high excitation energies ($\gtrsim$100 K) from the vicinity of the protostars, indicating the NH$_3$ ice has sublimated at the inner hot region. The NH$_3$ column density is estimated to be $\sim 10^{17}-10^{18}$ cm$^{-2}$. We also detected two NH$_2$D transitions, allowing us to constrain the deuterium fractionation of ammonia. The NH$_2$D/NH$_3$ ratios are as high as $\sim 0.3-1$ in both 4A1 and 4A2. From the comparisons with the astrochemical models in the literature, the high NH$_2$D/NH$_3$ ratios suggest that the formation of NH$_3$ ices mainly started in the prestellar phase after the formation of bulk water ice finished, and that the primary nitrogen reservoir in the star-forming cloud could be atomic nitrogen (or N atoms) rather than nitrogen-bearing species such as N$_2$ and NH$_3$. The implications on the physical properties of IRAS4A cores are discussed as well.

Outflows in active galactic nuclei (AGN) are considered a promising candidate for driving AGN feedback at large scales. However, without information on the density of these outflows, we cannot determine how much kinetic power they are imparting to the surrounding medium. Monitoring the response of the ionisation state of the absorbing outflows to changes in the ionising continuum provides the recombination timescale of the outflow, which is a function of the electron density. We have developed a new self-consistent time-dependent photoionisation model, TPHO, enabling the measurement of the plasma density through time-resolved X-ray spectroscopy. The algorithm solves the full-time-dependent energy and ionisation balance equations in a self-consistent fashion for all the ionic species. The model can therefore reproduce the time-dependent absorption spectrum of ionized outflows responding to changes in the ionizing radiation of the AGN. We find that when the ionised gas is in a non-equilibrium state its transmitted spectra are not accurately reproduced by standard photoionisation models. Our simulations with the current X-ray grating observations show that the spectral features identified as a multiple-components warm absorber, might be in fact features of a time-changing warm absorber and not distinctive components. The TPHO model facilitates accurate photoionisation modelling in the presence of a variable ionising source, thus providing constraints on the density and in turn the location of the AGN outflows. Ascertaining these two parameters will provide important insight into the role and impact of ionised outflows in AGN feedback.

The discovery of a non-thermal radio ring of low surface brightness about one degree in diameter has been recently reported around the location in the sky of the Calvera pulsar, at a high Galactic latitude. The radio properties point to it likely being a new supernova remnant (SNR), G118.4+37.0. We report an analysis of almost 14 years of observations of this region by the gamma-ray Large Area Telescope onboard the Fermi satellite. We detect extended GeV emission consistent with the size and location of the radio source, which confirms the presence of relativistic particles. The spectrum of the high-energy emission is fully compatible with an origin in the same relativistic particles producing the radio emission. These features and its similarities to other isolated SNRs establish this source as the remnant of a supernova. A simple model of the non-thermal emission from radio to GeV energies resulting from leptonic emission from electrons produced by the SNR is presented. G118.4+37.0 and other similar isolated remnants could be part of a radio-dim SNR population evolving in low density environments showing hard GeV emission of leptonic origin. Future deeper surveys in radio and gamma-rays could discover new members of the group.

Aims. With the next generation of large surveys coming to the stage of observational cosmology soon, it is important to explore their potential synergies and to maximise their scientific outcomes. In this study, we aim to investigate the complementarity of the two upcoming space missions Euclid and the China Space Station Telescope (CSST), focusing on weak lensing (WL) cosmology. In particular, we analyse the photometric redshifts (photo-zs) and the galaxy blending effects. For Euclid, WL measurements suffer from chromatic PSF effects. For this, CSST can provide valuable information for Euclid to obtain more accurate PSF, and to calibrate the color and color-gradient biases for WL measurements. Methods. We create image simulations for different surveys, and quantify the photo-z performance. For blending analyses, we employ high-resolution HST/CANDELS data to mock Euclid, CSST, and an LSST-like survey. We analyse the blending fraction for different cases, and the blending effects on galaxy photometry. Furthermore, we demonstrate that CSST can provide a large enough number of high SNR multi-band galaxy images to calibrate the color-gradient biases for Euclid. Results. The sky coverage of Euclid lies entirely within the CSST footprint. The combination of Euclid with CSST data can be done more uniformly than with the various ground-based data. Our studies show that by combining Euclid and CSST, we can reach a photo-z precision of $\sigma_{\rm NMAD} \approx 0.04$, and an outlier fraction of $\eta\approx 2.4\%$. Because of the similarly high resolutions, the data combination of Euclid and CSST can be relatively straightforward for photometry. To include ground-based data, however, sophisticated deblending utilizing priors from high-resolution space data is demanded. The color-gradient biases for Euclid can be well calibrated to the level of 0.1% using galaxies from CSST deep survey.

Kuiper Belt Objects, or more generally Trans-Neptunian Objects (TNOs), are planetesimals found beyond the orbit of Neptune. Some TNOs evolve onto Neptune-crossing orbits and become Centaurs. Many Centaurs, in turn, reach Jupiter-crossing orbits and become Jupiter-family comets (JFCs). TNOs are the main source of the JFCs. TNOs offer a different window than the JFCs, of more primordial bodies and over a different size and temperature range. It is in that context that this chapter is written. Here we discuss the dynamical pathways taken from the trans-Neptunian region to the JFCs, and the most important properties of TNOs that relate to the JFC population, including considerations of their origins, compositions, morphologies, and size distributions. We relate these properties to the JFCs whenever possible. We reflect on a few key outstanding issues regarding our incomplete knowledge of TNOs as they pertain to the Centaurs and JFC populations. We finish with a short discussion of notable new and upcoming facilities and the impacts they will have regarding these outstanding questions.

The origin of 3He abundance enhancements in coronal mass ejection (CME)-driven shock gradual solar energetic particle (SEP) events remains largely unexplained. Two mechanisms have been suggested - the re-acceleration of remnant flare material in interplanetary space and concomitant activity in the corona. We explore the first gradual SEP event with enhanced 3He abundance observed by Solar Orbiter. The event started on 2020 November 24 and was associated with a relatively fast halo CME. During the event, the spacecraft was at 0.9 au from the Sun. The event averaged 3He/4He abundance ratio is 24 times higher than the coronal or solar wind value, and the 3He intensity had timing similar to other species. We inspected available imaging, radio observations, and spacecraft magnetic connection to the CME source. It appears the most probable cause of the enhanced 3He abundance are residual 3He ions remaining from a preceding long period of 3He-rich SEPs on 2020 November 17-23.

Detecting cosmological signals from the Epoch of Reionization (EoR) requires high-precision calibration to isolate the cosmological signals from foreground emission. In radio interferometery, perturbed primary beams of antenna elements can disrupt the precise calibration, which results in contaminating the foreground-free region, or the EoR window, in the cylindrically averaged power spectrum. For Hydrogen Epoch of Reionization Array (HERA), we simulate and characterize the perturbed primary beams induced by feed motions such as axial, lateral, and tilting motions, above the 14-meter dish. To understand the effect of the perturbed beams, visibility measurements are modeled with two different foreground components, point sources and diffuse sources, and we find different feed motions present a different reaction to each type of sky source. HERA's redundant-baseline calibration in the presence of non-redundant antenna beams due to feed motions introduces chromatic errors in gain solutions, which produces foreground power leakage into the EoR window. The observed leakage from vertical feed motions comes predominately from point sources around zenith. Furthermore, the observed leakage from horizontal and tilting feed motion comes predominately from the diffuse components near the horizon. Mitigation of chromatic gain errors will be necessary for robust detection of the EoR signals with minimal foreground bias, and this will be discussed in the subsequent paper.

We propose to design and build an algorithm that will use a Convolutional Neural Network (CNN) and observations from the Unistellar network to reliably detect asteroid occultations. The Unistellar Network, made of more than 10,000 digital telescopes owned by citizen scientists, and is regularly used to record asteroid occultations. In order to process the increasing amount of observational produced by this network, we need a quick and reliable way to analyze occultations. In an effort to solve this problem, we trained a CNN with artificial images of stars with twenty different types of photometric signals. Inputs to the network consists of two stacks of snippet images of stars, one around the star that is supposed to be occulted and a reference star used for comparison. We need the reference star to distinguish between a true occultation and artefacts introduced by poor atmospheric condition. Our Occultation Detection Neural Network (ODNet), can analyze three sequence of stars per second with 91\% of precision and 87\% of recall. The algorithm is sufficiently fast and robust so we can envision incorporating onboard the eVscopes to deliver real-time results. We conclude that citizen science represents an important opportunity for the future studies and discoveries in the occultations, and that application of artificial intelligence will permit us to to take better advantage of the ever-growing quantity of data to categorize asteroids.

We examine the flux density ratio anomaly in the quadruply-imaged strong gravitational lens, B1422+231, and consider the contribution of $10-10^3M_{\odot}$ primordial black holes (PBHs) as a potential dark matter constituent. We describe the first flux density ratio measurement of B1422+231 in the millimeter-wave band using the Atacama Large Millimeter Array (ALMA). This fills an important multi-wavelength gap in our knowledge of this key lensed system. The flux density of the quasar at 233 GHz is dominated by synchrotron emission and the source size is estimated to be 66.9 pc. The observed flux density ratios at 233 GHz are similar to those measured in radio, mid-infrared and optical bands, which cannot be explained by a simple smooth mass model of the lens galaxy. We examine the probability of the flux density ratio anomaly arising from PBH microlensing using ray tracing simulations. The simulations consider the cases where 10% and 50% of dark matter are $10-10^3M_{\odot}$ PBHs with a power law mass function. Our analysis shows that the anomalous flux density ratio for B1422+231 can be explained by a lens model with a significant fraction of dark matter being PBHs. This study demonstrates the potential for new constraints on PBH dark matter using ALMA observations of multiply imaged strong gravitational lenses.

The intermediate mass black hole range, $10\lesssim M_{\rm BH}^{}/M_\odot^{}\lesssim 10^{5} $, has long offered enticing possibilities for primordial black holes (PBH), with populations in this range postulated to be responsible for some of the LIGO binary merger detected events as well as the existence of supermassive black holes embedded at galactic centers. However, a prominent bound derived from PBH accretion during recombination severely restricts the mass fraction of intermediate mass PBH. We address this problem by proposing a formation scenario in which "primordial" black holes form late in our cosmological history, beyond the CMB era, and bypassing this bound. During this crucial epoch, our population of compact objects exist as thermal balls supported by thermal pressure, which eventually cool to Fermi balls supported by degeneracy pressure and finally collapse to PBH. Furthermore, we present the remarkable possibility of PBH formation after the present era, which we term future PBH. Such a population would evade most, if not all bounds on the PBH mass spectrum in the literature and open up previously unthought-of possibilities. Light future PBH could form below the Hawking evaporation threshold and convert the bulk of the matter in the Universe into radiation.

In this paper, we investigate the primordial black hole (PBH) mass function with mass gap. Firstly, to obtain a data-supported PBH mass function with mass gap for subsolar masses PBHs, we fine-tune the coefficients of a model-independent power spectrum of primordial curvature perturbations. Then we take this unique PBH mass function into consideration and calculate the energy density spectrum of the stochastic gravitational wave background from PBH mergers. We find the location of its first peak almost has no relationship with the mass gap and is only determined by the probability distribution of frequencies at which PBH binaries merge. Apart from the first peak, there must be an accompanying smaller trough at higher frequency resulting from the mass gap. Therefore, the detection of this smaller trough will provide more information about inflation and PBH formation.

HectoMAP is a dense redshift survey of 95,403 galaxies based primarily on MMT spectroscopy with a median redshift $z = 0.345$. The survey covers 54.64 square degrees in a 1.5$^\circ$ wide strip across the northern sky centered at a declination of 43.25$^\circ$. We report the redshift, the spectral indicator D$_{n}$4000, and the stellar mass. The red selected survey is 81\% complete for 55,962 galaxies with $(g-r) > 1$ and $r <20.5$; it is 72\% complete for 32,908 galaxies with $(g-r) > 1$, $(r-i) > 0.5$ and $20.5 < r < 21.3$. The survey is a foundation for examining the quiescent galaxy population (63\% of the survey), clusters of galaxies, and the cosmic web. HectoMAP is completely covered by the HSC-SSP survey, thus enabling a variety of strong and weak lensing investigations. Comparison of the basis SDSS photometry with the HSC-SSP photometry demonstrates that HectoMAP provides complete magnitude limited surveys based on either photometric system.

We present a sample of 373 peaked-spectrum (PS) sources with spectral peaks around 150MHz, selected using a subset of two LOFAR all-sky surveys, the LOFAR Two Meter Sky Survey and the LOFAR LBA Sky Survey. These surveys are the most sensitive low-frequency widefield surveys to date, allowing us to select low-luminosity PS sources. Our sample increases the number of known PS sources in our survey area by a factor 50. The 5GHz luminosity distribution of our PS sample shows we sample the lowest luminosity PS sources to-date by nearly an order of magnitude. Since high-frequency PS sources and compact steep-spectrum sources are hypothesised to be the precursors to large radio galaxies, we investigate whether this is also the case for our sample of low-frequency PS sources. Using optical line emission criteria, we find that our PS sources are predominately high-excitation radio galaxies instead of low-excitation radio galaxies, corresponding to a quickly evolving population. We compute the radio source counts of our PS sample, and find they are scaled down by a factor of $\sim$40 compared to a general sample of radio-loud active galactic nuclei (AGN). This implies that the lifetimes of PS sources are 40 times shorter than large scale radio galaxies, if their luminosity functions are identical. To investigate this, we compute the first radio luminosity function for a homogeneously-selected PS sample. We find that for 144MHz luminosities $\gtrsim 10^{25}$W Hz$^{-1}$, the PS luminosity function has the same shape as an unresolved radio-loud AGN population but shifted down by a factor of $\sim$10. We interpret this as strong evidence that these high-luminosity PS sources evolve into large-scale radio-loud AGN. For local, low-luminosity PS sources, there is a surplus of PS sources, which we hypothesise to be the addition of frustrated PS sources that do not evolve into large-scale AGN.

The pressure and energy density of the gas and magnetic field inside solar coronal mass ejections (in relation to that in the ambient solar wind) is thought to play an important role in determining their dynamics as they propagate through the heliosphere. We compare the specific energy (${\rm erg\,g^{-1}}$) [comprising kinetic ($H_{\rm k}$), thermal ($H_{\rm th }$) and magnetic field ($H_{\rm mag}$) contributions] inside MCs and the solar wind background. We examine if the excess thermal + magnetic pressure and specific energy inside MCs (relative to the background) is correlated with their propagation and internal expansion speeds. We ask if the excess thermal + magnetic specific energy inside MCs might make them resemble rigid bodies in the context of aerodynamic drag. We use near-Earth in-situ data from the WIND spacecraft to identify a sample of 152 well observed interplanetary coronal mass ejections and their MC counterparts. We compute various metrics using these data to address our questions. We find that the total specific energy ($H$) inside MCs is approximately equal to that in the background solar wind. We find that the the excess (thermal + magnetic) pressure and specific energy are not well correlated with the near-Earth propagation and expansion speeds. We find that the excess thermal+magnetic specific energy $\gtrsim$ the specific kinetic energy of the solar wind incident on 81--89 \% of the MCs we study. This might explain how MCs retain their structural integrity and resist deformation by the solar wind bulk flow.

We present an occultation study of compact radio sources by the plasma tail of interstellar Comet 2I/Borisov (C/2019 Q4) both pre- and near-perihelion using the Arecibo and Green Bank radio telescopes. The interplanetary scintillation (IPS) technique was used to probe the plasma tail at P-band (302--352 MHz), 820 MHz, and L-band (1120--1730 MHz). The presence and absence of scintillation at different perpendicular distances from the central axis of the plasma tail suggests a narrow tail of less than 6~arcmin at a distance of $\sim$10~arcmin ($\sim$$10^6$~km) from the comet nucleus. Data recorded during the occultation of B1019+083 on 31 October 2019 with the Arecibo Telescope covered the width of the plasma tail from its outer region to the central axis. The systematic increase in scintillation during the occultation provides the plasma properties associated with the tail when the comet was at its pre-perihelion phase. The excess level of L-band scintillation indicates a plasma density enhancement of $\sim$15--20 times that of the background solar wind. The evolving shape of the observed scintillation power spectra across the tail from its edge to the central axis suggests a density spectrum flatter than Kolmogorov, and that the plasma-density irregularity scales present in the tail range between 10 and 700 km. The discovery of a high-frequency spectral excess, corresponding to irregularity scales much smaller than the Fresnel scale, suggests the presence of small-scale density structures in the plasma tail, likely caused by interaction between the solar wind and the plasma environment formed by the comet.

The trigger logic of the Tracking Ultraviolet Setup (TUS) and Multiwavelength Imaging New Instrument for the Extreme Universe Space Observatory (Mini-EUSO) space-based projects of the Joint Experiment Missions - EUSO (JEM-EUSO) program is summarized. The performance results on the search for ultra-high energy cosmic rays are presented.

The fast Fourier transform (FFT) based periodicity search methods provide an efficient way to search for millisecond and binary pulsars but encounter significant sensitivity degradation while searching for long period and short duty cycle pulsars. An alternative to FFT-based search methods called the Fast Folding Algorithm (FFA) search, provides superior sensitivity to search for signals with long periods and short duty cycles. In the GMRT High Resolution Southern Sky (GHRSS) survey, we are using an FFA-based pipeline to search for isolated pulsars in a period range of 100 ms to 100 s. We have processed 2800 degree$^2$ of the sky coverage away from the Galactic plane and discovered 6 new pulsars. Here, we report the discovery of 4 of these pulsars with the FFA search pipeline. This includes a narrow duty cycle pulsar, J1936$-$30, which shows nulling behavior with an extreme nulling fraction of $\sim 90\%$. Two of the GHRSS discoveries from the FFA search lie in narrow duty cycle ranges beyond the limit of the existing population. The implementation of FFA search in the GHRSS survey and other pulsar surveys is expected to recover the missing population of long period and short duty cycle pulsars.

We observed the scintillation pattern of nine bright pulsars at 324 MHz and three at 1.68 GHz and analyzed the wavenumber spectrum which is related to electron density variations of the plasma turbulence of the interstellar medium. For all pulsars the frequency section of the autocorrelation function of the dynamic spectra to at least 45\% of the maximum corresponds to predictions of scattering theories with a range of power-law exponents of the wavenumber spectrum of $3.56 \leq \alpha \leq 3.97$ with errors $\leq 0.05$ and a mean with standard deviation of $3.76\pm0.13$. The range includes $\alpha=3.67$ for the Kolmogorov spectrum. Similar results although with larger errors were found from the Fourier transform of the autocorrelation functions down to $\sim 10^{-3}$ of the maximum. No clear case of a distinction between thin-screen and extended-medium scattering models was found. The average frequency profile of the scintles can be characterized for steep wavenumber spectra with $\alpha\lesssim4$ by a cusp with a somewhat rounded peak. For flatter spectra, down to at least $\alpha\sim 3.56$ the cusp with its peak becomes more pronounced and its decay steepens. We discuss our findings in the context of scattering characteristics of the interstellar medium.

We revisit the full variety of observed temporal and spatial distributions of energetic solar protons in "gradual" solar energetic-particle (SEP) events resulting from the spatial variations in the shock waves that accelerate them. Differences in the shock strength at the solar longitude of a spacecraft and at the footpoint of its connecting magnetic field line, nominally 55 degrees to the west, drive much of that variation. The shock wave itself, together with energetic particles trapped near it by self-amplified Alfven waves, forms an underlying autonomous structure that can drive across magnetic field lines intact, spreading proton intensities in a widening SEP longitude distribution. During the formation of this fundamental structure, historically called an "energetic storm particle" (ESP) event, many SEPs leak away early, amplifying waves as they flow along well-connected field lines and broaden the distribution outward; behind this structure between the shock and the Sun a "reservoir" of quasi-trapped SEPs forms. Very large SEP events are complicated by additional extensive wave growth that can spread an extended ESP-like trapping region. The multiplicity of shock-related processes contributing to the observed SEP profiles causes correlations of the events to be poorly represented by the peak intensities commonly used. In fact, the extensive spatial distributions of SEPs are sometimes interwoven with the structures of the shocks that have accelerated them and sometimes free. We should consider new questions: Which extremes of the shock contribute most to the SEPs profile of an event, (1) the shock at the longitude of a spacecraft, (2) the shock ~55 degrees to the west at the footpoint of the field, or (3) SEPs that have collected in the reservoir? How does the space-time distribution of SEPs correspond with the underlying space-time distribution of shock strength?

The connection between the escape fraction of ionizing radiation ($f_{esc}$) and the properties of galaxies, such as stellar mass (M*), age, star-formation rate (SFR), and dust content, are key inputs for reionization models, but many of these relationships remain untested at high redshift. We present an analysis of a sample of 96 z~3 galaxies from the Keck Lyman Continuum Spectroscopic Survey (KLCS). These galaxies have both sensitive Keck/LRIS spectroscopic measurements of the Lyman continuum (LyC) region, and multi-band photometry that places constraints on stellar population parameters. We construct composite spectra from subsamples binned as a function of galaxy property and quantify the ionizing-photon escape for each composite. We find a significant anti-correlation between $f_{esc}$ and M*, consistent with predictions from cosmological zoom-in simulations. We also find significant anti-correlation between $f_{esc}$ and E(B-V), encoding the underlying physics of LyC escape in our sample. We also find no significant correlation between $f_{esc}$ and either stellar age or specific SFR (=SFR/M*), challenging interpretations that synchronize recent star formation and favorable conditions for ionizing escape. The galaxy properties now shown to correlate with $f_{esc}$ in the KLCS are Ly$\alpha$ equivalent width, UV Luminosity, M*, SFR, and E(B-V), but not age or sSFR. To date, this is the most comprehensive analysis of galaxy properties and LyC escape at high redshift, and will be used to guide future models and observations of the reionization epoch.

The low-redshift mass-metallicity relation (MZR) is well studied, but the high-redshift MZR remains difficult to observe. To study the early MZR further, we analyze the Cosmic Reionization on Computers (CROC) simulations with a focus on the MZR from redshifts 5 to 10. We find that, across all redshifts, CROC galaxies exhibit similar stellar-phase and gas-phase MZRs that flatten with higher stellar mass. We attribute this flattening to the inaccurate star formation and feedback modeling in CROC (star formation is overly suppressed in massive CROC galaxies). In addition, we show that the ratio between stellar metallicity and gas metallicity ($Z_*/Z_{gas}$) decreases as stellar age increases, meaning that in CROC galaxies, gas accretion rate is lower than metal production rate. With JWST we will be able to compare our predictions to observations of the Epoch of Reionization and understand better early galaxy formation.

Observations of galaxy-scale strong gravitational lensing (SGL) systems have enabled unique tests of nonlinear departures from general relativity (GR) on the galactic and supergalactic scales. One of the most important cases of such tests is constraints on the gravitational slip between two scalar gravitational potentials. In this paper, we use a newly compiled sample of strong gravitational lenses to test the validity of GR, focusing on the screening effects on the apparent positions of lensed sources relative to the GR predictions. This is the first simultaneous measurement of the Post-Newtonian (PN) parameter ($\gamma_{PN}$) and the screening radius ($\Lambda$) without any assumptions about the contents of the Universe. Our results suggest that the measured PPN is marginally consistent with GR ($\gamma_{PN}=1$) with increasing screening radius ($\Lambda = 10-300 $kpc), although the choice of lens models may have a significant influence on the final measurements. Based on a well-defined sample of 5000 simulated strong lenses from the forthcoming LSST, our methodology will provide a strong extragalactic test of GR with an accuracy of 0.5\%, assessed up to scales of $\Lambda \sim 300$ kpc. For the current and future observations of available SGL systems, there is no noticeable evidence indicating some specific cutoff scales on kpc-Mpc scales, beyond which new gravitational degrees of freedom are expressed.

We observed 20 Palomar-Green (PG) quasars at low redshift ($z<0.5$) with total flux density > 1 mJy, including 4 radio-loud quasars (RLQs) and 16 radio-quiet quasars (RQQs), using the Very Long Baseline Array (VLBA) at 5 GHz. Ten RQQs are clearly detected in the VLBA images, and a compact radio core is identified in eight of them, indicating the prevalence of active galactic nucleus (AGN)-related radio emission in this flux-density-limited RQQ sample. The RQQs and RLQs in our sample have a division at $\sim$30~mJy. The radio emission from RQQs appears to be the result of a combination of star formation and AGN-associated activities. All RQQs in our sample have a 5 GHz flux density ratio of Very Large Array (VLA) A-array to D-array $f_{\rm c} = S_{\rm A}^{\rm VLA}/S_{\rm D}^{\rm VLA}$ above 0.2. The RQQs with $f_a$ (VLBA and VLA flux density ratio $S^{\rm VLBA}/S_{\rm A}^{\rm VLA}) > 0.2$ versus $f_a < 0.2$ show significant differences in morphology, compactness and total flux density. $f_{\rm a}$ of RQQs is systematically lower than that of RLQs, probably due to the extended jets or relic jets of RQQs on 10s to 100s parsecs which are resolved out in VLBA images. Future larger samples, especially with the addition of milli-arcsec resolution radio images of RQQs with total flux densities below 1 mJy, can test the conclusions of this paper and contributes to the understanding of the radio emission mechanism of RQQs, and the dichotomy and physical connection between RQQs and RLQs.

The free-free absorption of low frequency radio waves by thermal electrons in the warm ionized medium of our Galaxy becomes very significant at $\lesssim 10$ MHz (ultralong-wavelength), and the absorption strength depends on the radio frequency. Upcoming space experiments such as the Discovering Sky at the Longest wavelength (DSL) and Farside Array for Radio Science Investigations of the Dark ages and Exoplanets (FARSIDE) will produce high-resolution multi-frequency sky maps at the ultralong-wavelength, providing a new window to observe the Universe. In this paper we propose that from these ultralong-wavelength multi-frequency maps, the three-dimensional distribution of the Galactic electrons can be reconstructed. This novel and robust reconstruction of the Galactic electron distribution will be a key science case of those space missions. Ultralong-wavelength observations will be a powerful tool for studying the astrophysics relevant to the Galactic electron distribution, for example, the impacts of supernova explosions on electron distribution, and the interaction between interstellar atoms and ionizing photons escaped from the HII regions around massive stars.

Cosmology models predict that external accretion shocks form in the outer region of galaxy clusters due to supersonic gas infall from filaments and voids in the cosmic web. They are characterized by high sonic and Alfv\'enic Mach numbers, $M_s\sim10-10^2$ and $M_A\sim10^2-10^3$, and propagate into weakly magnetized plasmas of $\beta\equiv P_g/P_B\gtrsim10^2$. Although strong accretion shocks are expected to be efficient accelerators of cosmic rays (CRs), nonthermal signatures of shock-accelerated CRs around clusters have not been confirmed, and detailed acceleration physics at such shocks has yet to be understood. In this study, we first establish through two-dimensional particle-in-cell simulations that at strong high-$\beta$ shocks electrons can be pre-energized via stochastic Fermi acceleration owing to the ion-Weibel instability in the shock transition region, possibly followed by injection into diffusive shock acceleration. Hence, we propose that the models derived from conventional thermal leakage injection may be employed for the acceleration of electrons and ions at accretion shocks as well. Applying these analytic models to numerical shock zones identified in structure formation simulations, we estimate nonthermal radiation, such as synchrotron and inverse-Compton (IC) emission due to CR electrons, and $\pi^0$-decay $\gamma$-rays due to CR protons, around simulated clusters. Our models with the injection parameter, $Q\approx3.5-3.8$, predict synthetic synchrotron maps, which seem consistent with recent radio observations of the Coma cluster. However, the detection of nonthermal IC X-rays and $\gamma$-rays from accretion shocks would be quite challenging. We suggest that the proposed analytic models may be adopted as generic recipes for CR production at cosmological shocks.

By using the LAMOST time-domain survey data, we study stellar activities based on the $\rm{H_{\alpha}}$ lines for about 2000 stars in four $K$2 plates. Two indices, $R_{\rm{H\alpha}}^{'}$ and $R_{\rm{H\alpha}}^{+}$, are computed from LAMOST spectra, the former of which is derived by excluding the photospheric contributions to the $\rm{H_{\alpha}}$ lines, while the latter is derived by further subtracting the non-dynamo driven chromospheric emission. Meanwhile, the periodicity and variation amplitudes are computed from \emph{K2} light curves. Both the $R_{\rm{H\alpha}}^{'}$-Ro relation and $R_{\rm{H\alpha}}^{+}$-Ro relation show complicated profiles in the non-saturated decay region. Hot stars show flatter slopes and higher activity level than cool stars, and the behaviour is more notable in the $R_{\rm{H\alpha}}^{+}$-$R_{o}$ relation. This is consistent with recent studies using other activity proxies, including $L_{\rm{x}}/L_{\rm{bol}}$, $R_{\rm{HK}}^{'}$ and amplitudes of optical light curves. % This may suggest different kinds of stars follow different power laws in the decay region. Most of our targets have multiple observations, and some of them exhibit significant variability of ${\rm{H\alpha}}$ emissions, which may cause the large scatters shown in the decay region. We find three targets exhibiting positive correlation in rotational phase, possibly indicating that their optical light curves are dominated by hot faculae rather than cool starspots.

The fluctuations in the dark matter-baryon relative velocity field are imprinted as acoustic oscillations in the 21-cm power spectrum during cosmic dawn (CD). These velocity acoustic oscillations (VAOs) keep the imprints of the comoving sound horizon scale. In a previous work by Mu\~noz, it has been demonstrated that these VAOs can be treated as standard rulers to measure the cosmic expansion rate at high redshifts by considering a variety of Lyman-Werner feedback strengths and foreground contamination scenarios. Here we extend that analysis by using a modified version of the public code \texttt{21cmFAST}. We use this code to simulate the VAOs in 21-cm power spectrum and forecast the potential to constrain $H(z)$ with the HERA radio telescope, taking into account the effects of Lyman-$\alpha$ heating, Lyman-Werner feedback and foregrounds, the dependence on various astrophysical parameters, and the degeneracy with cosmological parameters. We find that $H(z)$ can be measured with HERA at $\sim 0.3-6\%$ relative accuracy in the range $11 < z < 20$, under different astrophysical and foreground scenarios, with uncertainties in the Planck cosmological parameters setting a $\sim 0.08-0.2\%$ relative-error floor in the measurement. This accuracy is on par with most low-redshift measurements and can be helpful in testing various cosmological scenarios motivated by the ongoing ``Hubble Tension".

Using four mixed bivariate distributions (Normal distribution, Skew-Normal distribution, Student distribution, Skew-Student distribution) and bootstrap re-sampling analysis, we analyze the samples of CGRO/BATSE, Swift/BAT and Fermi/GBM gamma-ray bursts in detail on the t90-hardness ratio plane. The Bayesian information criterion is used to judge the goodness of fit for each sample, comprehensively. It is found that all the three samples show a symmetric (either normal or student) distribution. It is also found that the existence of three classes of gamma-ray bursts is preferred by the three samples, but the strength of this preference varies with the sample size: when the sample size of the data set is larger, the preference of three classes scheme becomes weaker. Therefore, the appearance of an intermediate class may be caused by a small sample size and the possibility that there are only two classes of gamma-ray bursts still cannot be expelled yet. A further bootstrap re-sampling analysis also confirms this result.

We present broadband radio flux-density measurements supernova (SN) 1996cr, made with MeerKAT, ATCA and ALMA, and images made from very long baseline interferometry (VLBI) observations with the Australian Long Baseline Array. The spectral energy distribution of SN 1996cr in 2020, at age, $t \sim$8700 d, is a power-law, with flux density, $S\propto \nu^{-0.588 \pm 0.011}$ between 1 and 34 GHz, but may steepen at $>35$ GHz. The spectrum has flattened since $t = 5370$ d (2010). Also since $t = 5370$ d, the flux density has declined rapidly, with $S_{\rm 9 GHz} \propto t^{-2.9}$. The VLBI image at $t = 8859$ d shows an approximately circular structure, with a central minimum reminiscent of an optically-thin spherical shell of emission. For a distance of 3.7 Mpc, the average outer radius of the radio emission at that time was $(5.1 \pm 0.3) \times 10^{17}$ cm, and SN 1996cr has been expanding with a velocity of $4650 \pm 1060$ km s$^{-1}$ between $t=4307$ and 8859 d. It must have undergone considerable deceleration before $t = 4307$ d. Deviations from a circular shell structure in the image suggest a range of velocities up to $\sim$7000 km s$^{-1}$, and hint at the presence of a ring- or equatorial-belt-like structure rather than a complete spherical shell.

Supernovae and their remnants provide energetic feedback to the ambient interstellar medium (ISM), which is often distributed in multiple gas phases. Among them, warm molecular hydrogen (H$_2$) often dominates the cooling of the shocked molecular ISM, which has been observed with the H$_2$ emission lines at near-infrared wavelengths. Such studies, however, were either limited in narrow filter imaging or sparsely sampled mid-infrared spectroscopic observations with relatively poor angular resolutions. Here we present near-infrared ($H$- and $K$-band) spectroscopic mosaic observations towards the A, B, C, and G regions of the supernova remnant (SNR) IC 443, with the K-band Multi-Object Spectrograph (KMOS) onboard the Very Large Telescope (VLT). We detected 20 ro-vibrational transitions of H$_2$, one H line (Br$\gamma$), and two [Fe II] lines, which dominate broadband images at both $H$- and $K$-band. The spatial distribution of H$_2$ lines at all regions are clumpy on scales from $\sim 0.1$ pc down to $\sim 0.008$ pc. The fitted excitation temperature of H$_2$ is between 1500 K and 2500 K, indicating warm shocked gas in these regions. The multi-gas-phase comparison shows stratified shock structures in all regions, which explains the co-existence of multiple types of shocks in the same regions. Last, we verify the candidates of young stellar objects previously identified in these regions with our spectroscopic data, and find none of them are associated with young stars. This sets challenges to the previously proposed scenario of triggered star formation by SNR shocks in IC~443.

[Abridged] This review paper discussed which chemical effects may be at play in a planet-forming disk midplane, which effects are relevant under different conditions, and which tools are available for modelling chemical kinetics in a disk midplane. The review goes on to discuss some important efforts in the planet formation modelling community to treat chemical evolution, and, vice versa, efforts in the chemical modelling community to implement more physical effects related to planet formation into the chemical modelling. The aim of this review is both to outline some concepts related to planet formation chemistry, but also to encourage, not just collaboration between the planet formation modelling community and the astrochemical community, but also assistance and guidance from one community to the other. Guidance, regarding which effects, out of many, might be more relevant than others under certain planet formation conditions, and regarding why certain included effects lead to certain important modelling outcomes. As the research fields of exoplanet atmospheres and protoplanetary disks near new frontiers in observational insights with upcoming facilities, developing appropriate modelling frameworks (including physical and chemical effects) is paramount to ultimately enable the linking of a chemically characterised exoplanet atmospheres to its formation history in its natal protoplanetary disk.

We report the discovery of two companion sources to a strongly lensed galaxy SPT0418-47 ("ring") at redshift 4.225, targeted by the JWST Early Release Science program. We confirm that these sources are at a similar redshift as the ring based on H$\alpha$ detected in the NIRSpec spectrum, and [C II] 158 $\mu$m line from ALMA. Using multiple spectral lines detected in JWST/NIRSpec, the rest-frame optical to infrared images from NIRCam and MIRI, and far-infrared (FIR) dust continuum detected by ALMA, we argue that the newly discovered sources are actually lensed images of the same companion galaxy, hereafter referred to as SPT0418-SE ("SE"), located within 5 kpc in the source plane of the ring. The star formation rate derived using [C II] and dust continuum puts a lower limit of 17 M$_\odot$/yr, while the SFR$_\mathrm{H\alpha}$ is estimated to be $\sim$200 times lower, thereby confirming that SE is a heavily dust obscured star-forming galaxy. Analysis using optical strong line diagnostics suggests that SE has near solar elemental abundance, while the ring appears to have super-solar metallicity O/H and N/O. We attempt to reconcile the high metallicity in this system by invoking early onset of star formation with continuous high star forming efficiency, or that optical strong line diagnostics need revision at high redshift. We suggest that SPT0418-47 resides in a massive dark matter halo with yet to be discovered neighbors. This work highlights the importance of joint analysis of JWST and ALMA data for a deep and complete picture of the early Universe.

White-light stellar flares are now reported by the thousands in long-baseline, high precision, broad-band photometry from missions like Kepler, K2, and TESS. These observations are crucial inputs for assessments of biosignatures in exoplanetary atmospheres and surface ultraviolet radiation dosages for habitable zone planets around low-mass stars. A limitation of these assessments, however, is the lack of near-ultraviolet spectral observations of stellar flares. To motivate further empirical investigation, we use a grid of radiative-hydrodynamic simulations with an updated treatment of the pressure broadening of hydrogen lines to predict the $\lambda \approx 1800-3300$ \AA\ continuum flux during the rise and peak phases of a well-studied superflare from the dM3e star AD Leo. These predictions are based on semi-empirical superpositions of radiative flux spectra consisting of a high-flux electron beam simulation with a large, low-energy cutoff ($\gtrsim 85$ keV) and a lower-flux electron beam simulation with a smaller, low-energy cutoff ($\lesssim 40$ keV). The two-component models comprehensively explain the hydrogen Balmer line broadening, the optical continuum color temperature, the Balmer jump strength, and the far-ultraviolet continuum strength and shape in the rise/peak phase of this flare. We use spatially resolved analyses of solar flare data from the Interface Region Imaging Spectrograph, combined with the results of previous radiative-hydrodynamic modeling of the 2014 Mar 29 X1 solar flare (SOL20140329T17:48), to interpret the two-component electron beam model as representing the spatial superposition of bright kernels and fainter ribbons over a larger area.

Gravitational collapse of dark matter overdensities leads to the formation of dark matter halos which embed galaxies and galaxy clusters. An intriguing feature of dark matter halos is that their density profiles closely follow a universal form irrespective of the initial condition or the corresponding growth history. This represents a class of dynamical systems with emergent universalities. We propose an ``iterative mean-field approach'' to compute the solutions of the gravitational collapse dynamics. This approach iteratively searches for the evolution of the interaction field $\phi(t)$ -- in this case the enclosed mass profile $M(r,t)$ -- that is consistent with the dynamics, thus that $\phi(t)$ is the fix-point of the iterative mapping, $\mathcal{H}(\phi) = \phi$. The formalism replaces the N-body interactions with one-body interactions with the coarse-grained interaction field, and thus shares the spirit of the mean-field theory in statistical physics. This ``iterative mean-field approach'' combines the versatility of numerical simulations and the comprehensiveness of analytical solutions, and is particularly powerful in searching for and understanding intermediate asymptotic states in a wide range of dynamical systems where the solutions can not be obtained through the traditional self-similar analysis.

The neutral atomic hydrogen (HI) mass function (HIMF) describes the distribution of the HI content of galaxies at any epoch; its evolution provides an important probe of models of galaxy formation and evolution. Here, we report Giant Metrewave Radio Telescope HI 21cm spectroscopy of blue star-forming galaxies at $z\approx0.20-0.42$ in the Extended Groth Strip, which has allowed us to determine the scaling relation between the average HI mass ($\rm{M_{HI}}$) and the absolute B-band magnitude ($\rm{M_B}$) of such galaxies at $z \approx 0.35$, by stacking the HI 21cm emission signals of galaxy subsamples in different $\rm{M_B}$ ranges. We combine this $\rm{M_{HI}-M_B}$ scaling relation (with a scatter assumed to be equal to that in the local Universe) with the known B-band luminosity function of star-forming galaxies at these redshifts to determine the HIMF at $z\approx0.35$. We show that the use of the correct scatter in the $\rm{M_{HI}-M_B}$ scaling relation is critical for an accurate estimate of the HIMF. We find that the HIMF has evolved significantly from $z\approx0.35$ to $z\approx0$, i.e. over the last four Gyr, especially at the high-mass end. High-mass galaxies, with $\rm{M_{HI}\gtrsim10^{10}\ M_\odot}$, are a factor of $\approx3.4$ less prevalent at $z\approx0.35$ than at $z \approx 0$. Conversely, there are more low-mass galaxies, with $\rm{M_{HI} \approx10^9\ {M}_\odot}$, at $z\approx0.35$ than in the local Universe. While our results may be affected by cosmic variance, we find that massive star-forming galaxies have acquired a significant amount of HI through merger events or accretion from the circumgalactic medium over the past four Gyr.

We present the effective-field theory (EFT)-based cosmological full-shape analysis of the anisotropic power spectrum of eBOSS quasars at the effective redshift $z_{\rm eff}=1.48$. We perform extensive tests of our pipeline on simulations, paying a particular attention to the modeling of observational systematics, such as redshift smearing, fiber collisions, and the radial integral constraint. Assuming the minimal $\Lambda$CDM model, and fixing the primordial power spectrum tilt and the physical baryon density, we find the Hubble constant $H_0=(66.7\pm 3.2)~$km~s$^{-1}$Mpc$^{-1}$, the matter density fraction $\Omega_m=0.32\pm 0.03$, and the late-time mass fluctuation amplitude $\sigma_8=0.95\pm 0.08$. These measurements are fully consistent with the Planck cosmic microwave background results. Our eBOSS quasar $S_8$ posterior, $0.98\pm0.11$, does not exhibit the so-called $S_8$ tension. Our work paves the way for systematic full-shape analyses of quasar samples from future surveys like DESI.

We present novel constraints on the underlying galaxy formation physics (e.g., mass loading factor, star formation history, metal retention) at $z \gtrsim 7$ for the low-mass ($M_*\sim10^5$ M$_\odot$) Local Group ultra-faint dwarf galaxy (UFD) Eridanus II (Eri II) Using a hierarchical Bayesian framework, we apply a one-zone chemical evolution model to Eri II's CaHK-based photometric metallicity distribution function (MDF; [Fe/H]) and find that the evolution of Eri II is well-characterized by a short, exponentially declining star-formation history ($\tau_\text{SFH} = 0.39\pm_{0.13}^{0.18}$ Gyr), a low star-formation efficiency ($\tau_\text{SFE} = 27.56\pm_{12.92}^{25.14}$ Gyr), and a large mass-loading factor ($\eta = 194.53\pm_{42.67}^{33.37}$). Our results are consistent with Eri II forming the majority of its stars before the end of reionization. The large mass-loading factor is consistent with strong outflows in Eri II and is in good agreement with theoretical predictions for momentum-driven galactic winds. It also results in the ejection of $>$90% of the metals produced in Eri II. We make predictions for the distribution of [Mg/Fe]-[Fe/H] in Eri II as well as the prevalence of ultra metal-poor stars, both of which can be tested by future chemical abundance measurements. Spectroscopic follow-up of the highest metallicity stars in Eri II ($\text{[Fe/H]}> -2$) will greatly improve model constraints. Our new framework can readily be applied to all UFDs throughout the Local Group, providing new insights in to the underlying physics governing the evolution of the faintest galaxies in the reionization-era.

At least one major merger is currently taking place in the MW. The Sgr dwarf spheroidal galaxy is being tidally destroyed while orbiting around the MW, whose close passages perturb the MW disc externally. In this work, using a series of hydrodynamical simulations, we investigate how massive dwarf galaxies on quasi-polar Sgr-like orbits impact the star formation activity inside the MW-like discs. First, we confirm that interactions with orbiting satellites enhance the star formation rate in the host galaxy. However, prominent short-time scale bursts are detected during the very close passages (<20 kpc) of massive (>2\times 10^{10} \Msun) gas-poor satellites. In the case of gas-rich satellites, while we see a substantial enhancement of the star formation on a longer time scale, we do not detect prominent peaks in the star formation history of the host. This can be explained by the steady accretion of gas being stripped from the satellite, which smoothens short-term variations in the star formation rate of the host. It is important that the impact of the satellite perturbations, especially its first encounters, is seen mainly in the outer~(>10 kpc) disc of the host. We also found that the close passages of satellites cause the formation of a substantial amount of low-metallicity stars in the host, and the effect is the most prominent in the case of gas infall from the satellites resulting in the dilution of the mean stellar metallicity soon after the first pericentric passage of massive satellites. Our simulations are in favour of causality between the recent passages of the Sgr galaxy and the bursts of the star formation in the solar neighbourhood~(\approx 1 and \approx 2 Gyr ago); however, in order to reproduce the SF burst at its first infall (\approx 6 Gyr), we require a very close pericentric passage (<20 kpc) with subsequent substantial mass loss of the Sgr precursor.

Solar flares are some of the most energetic events in the solar system and can be studied to investigate the physics of plasmas and stellar processes. One interesting aspect of solar flares is the presence of accelerated (nonthermal) particles, whose signatures appear in solar flare hard X-ray emissions. Debate has been ongoing since the early days of the space age as to how these particles are accelerated, and one way to probe relevant acceleration mechanisms is by investigating short-timescale (tens of milliseconds) variations in solar flare hard X-ray flux. The Impulsive Phase Rapid Energetic Solar Spectrometer (IMPRESS) CubeSat mission aims to measure these fast hard X-ray variations. In order to produce the best possible science data from this mission, we characterize the IMPRESS scintillator detectors using Geant4 Monte Carlo models. We show that the Geant4 Monte Carlo detector model is consistent with an analytical model. We find that Geant4 simulations of X-ray and optical interactions explain observed features in experimental data, but do not completely account for our measured energy resolution. We further show that nonuniform light collection leads to double-peak behavior at the 662 keV $^{137}$Cs photopeak and can be corrected in Geant4 models and likely in the lab.

Rotation may affect the occurrence of sustainable hydrogen burning in very low-mass stellar objects by the introduction of centrifugal force to the hydrostatic balance as well as by the appearance of rotational break-up of the objects (mass-shedding limit) for rapidly rotating cases. We numerically construct the models of rotating very low-mass stellar objects that may or may not experience sustained nuclear reaction (hydrogen-burning) as their energy source. The rotation is not limited to being slow so the effect of the rotational deformation of them is not infinitesimally small. Critical curves of sustainable hydrogen burning in the parameter space of mass versus central degeneracy, on which the nuclear energy generation balances the surface luminosity, are obtained for different values of angular momentum. It is shown that if the angular momentum exceeds the threshold $J_0=8.85\times 10^{48}{\rm erg}~{\rm s}$ the critical curve is broken up into two branches with lower and higher degeneracy because of the mass-shedding limit. Based on the results, we model mechano-thermal evolutions of substellar objects, in which cooling, as well as mass/angular momentum reductions, are followed for two simplified cases. The case with such external braking mechanisms as magnetized wind or magnetic braking is mainly controlled by the spin-down timescale. The other case with no external braking leads to the mass-shedding limit after gravitational contraction. Thereafter the object sheds its mass to form a ring or a disc surrounding it and shrinks.

We discuss the mechanism(s) of bar formation in isolated and tidally interacting disk galaxies using the results of idealized collisionless Nbody simulations of the galaxies. In order to better understand the mechanism, we investigate orbital eccentricities (e), epochs of apocenter passages (t_a), azimuthal angles at t_a (varphi_a), precession rates (Omega_pre), for individual stars, as well as bar strengths represented by relative m=2 Fourier amplitude (A_2) and bar pattern speeds (Omega_bar). The main results are as follows. A significant fraction of stars with initially different varphi_a and Omega_pre in an isolated disk galaxy can have similar values within several dynamical timescales. This synchronization of varphi_a and Omega_pre, which is referred to as apsidal precession synchronization (``APS'') in the present study, is caused by the enhanced strength of the tangential component of gravitational force. A weak seed bar (A_2<0.1) is first formed through APS in local regions of a disk, then the bar grows due to APS. In the bar growth phase (0.1<A_2<0.4), APS can proceed more efficiently due to stronger tangential force from the bar so that it can enhance the bar strength further. This positive feedback loop in APS is the key physical mechanism of bar growth in isolated stellar disks. Bar formation can be severely suppressed in disks with lower disk mass fractions and/or higher $Q$ parameters due to much less efficient APS. APS proceeds more rapidly and more efficiently due to strong tidal perturbation in the formation of tidal bars compared to spontaneous bar formation.

With a unique set of 54 overlapping narrow-band and two broader filters covering the entire optical range, the incoming Javalambre-Physics of the Accelerating Universe Astrophysical Survey (J-PAS) will provide a great opportunity for stellar physics and near-field cosmology. In this work, we use the miniJPAS data in 56 J-PAS filters and 4 complementary SDSS-like filters to explore and prove the potential of the J-PAS filter system in characterizing stars and deriving their atmospheric parameters. We obtain estimates for the effective temperature with a good precision (<150 K) from spectral energy distribution fitting. We have constructed the metallicity-dependent stellar loci in 59 colours for the miniJPAS FGK dwarf stars, after correcting certain systematic errors in flat-fielding. The very blue colours, including uJAVA-r, J0378-r, J0390-r, uJPAS-r, show the strongest metallicity dependence, around 0.25 mag/dex. The sensitivities decrease to about 0.1 mag/dex for the J0400-r, J0410-r, and J0420-r colours. The locus fitting residuals show peaks at the J0390, J0430, J0510, and J0520 filters, suggesting that individual elemental abundances such as [Ca/Fe], [C/Fe], and [Mg/Fe] can also be determined from the J-PAS photometry. Via stellar loci, we have achieved a typical metallicity precision of 0.1 dex. The miniJPAS filters also demonstrate strong potential in discriminating dwarfs and giants, particularly the J0520 and J0510 filters. Our results demonstrate the power of the J-PAS filter system in stellar parameter determinations and the huge potential of the coming J-PAS survey in stellar and Galactic studies.

The motion of cosmic strings in the universe leads to the generation of wakes behind them. We study magnetized wakes of cosmic strings moving in the post recombination plasma. We show that magnetic reconnection can occur in the post shock region. Since the width of the cosmic string wake is very small, the reconnection occurs over a very short lengthscale. The reconnection leads to a large amount of kinetic energy being released in the post shock region of the cosmic string wake. This enhances the kinetic energy released during the reconnection. We make a rudimentary estimate of the kinetic energy released by the magnetic reconnection in cosmic strings wakes and show that it can account for low energy Gamma Ray Bursts (GRB) in the post recombination era.

NGC5128 galaxy is a giant elliptical galaxy located in the Centaurus group of galaxies at 3.8 Mpc. We aim to study the star formation history (SFH) of two different fields of the galaxy. The northeastern field (Field 1) is located at a distance of 18.8 kpc, while the southern field (Field 2) is at 9.9 kpc. We use a photometric method that is based on identifying long period variable (LPV) stars and asymptotic giant branch (AGB) stars, as they are strong tracers of star formation and galaxy evolution due to their luminosity and variability; 395 LPVs in Field 1 and 671 LPVs in Field 2 have been identified. These two fields present similar SFHs, although the SF rate of Field 2 is more enhanced. We find that the galaxy has three major star formation episodes t $\sim$ 800 Myr ago, t $\sim$ 3.2 Gyr ago, and t $\sim$ 10 Gyr ago, where t is look-back time. The rate of star formation at $\sim$ 800 Myr ago agrees with previous studies suggesting that the galaxy experienced a merger around that time. Furthermore, NGC5128 has experienced a lower star formation rate in its recent history which could have been driven by jet-induction star formation and multiple outbursts of AGN activity in this galaxy, as well as a minor merger around 400 Myr ago.

We find several missing one-loop-order contributions in previous considerations about secondary gravitational waves induced at nonlinear order in cosmological perturbations. We consider a consistent perturbative expansion to third-order in cosmological perturbations, including higher-order interactions and iterative solutions ignored in the previous literature. Tensor fluctuations induced by the source with two scalar and one tensor perturbations are correlated with the first-order tensor fluctuation and thus give a one-loop-order correction to the tensor power spectrum. The missing loop correction is \textit{scale-invariant} and \textit{negative} in the superhorion region, which secondarily reduces the initial primordial tensor power spectrum prior to the horizon re-entry. Such an IR behavior is very different from the auto-spectrum of second-order induced tensor modes discussed in the previous literature and can be important for the actual gravitational wave measurements. For a sharp peak of scalar fluctuations with $A_\zeta=10^{-2}$ at $k_*=10^{5}h/{\rm Mpc}$ motivated by the LIGO/Virgo events, we show that the tensor power spectrum at the cosmic microwave background scale reduces by at most 35%. Hence, the polarization B-mode might not be seen because of the reduction of the original tensor spectrum due to the secondary effect of primordial black hole formation.

We use the most recent data release (DR9) of the DESI legacy imaging survey and SDSS galaxy groups to measure the conditional luminosity function (CLF) for groups with halo mass $M_{\rm h}\ge 10^{12}M_{\odot}$ and redshift $0.01\le z\le 0.08$, down to a limiting $r$-band magnitude of $M_{\rm r}=-10\sim-12$. For a given halo mass we measure the CLF for the total satellite population, as well as separately for the red and blue populations classified using the $(g-z)$ color. We find a clear faint-end upturn in the CLF of red satellites, with a slope $\alpha\approx-1.8$ which is almost independent of halo mass. This faint-end upturn is not seen for blue satellites and for the total population. Our stellar population synthesis modeling shows that the $(g-z)$ color provides a clean red/blue division, and that group galaxies in the red population defined by $(g-z)$ are all dominated by old stellar populations. The fraction of old galaxies as a function of galaxy luminosity shows a minimum at a luminosity $M_{\rm r}\sim-18$, corresponding to a stellar mass $M_\ast\sim10^{9.5}M_\odot$. This mass scale is independent of halo mass and is comparable to the characteristic luminosity at which galaxies show a dichotomy in surface brightness and size, suggesting that the dichotomy in the old fraction and in galaxy structure may have a common origin. The rising of the old fraction at the faint end for Milky Way (MW)-sized halos found here is in good agreement with the quenched fraction measured both for the MW/M31 system and from the ELVES survey. We discuss the implications of our results for the formation and evolution of low-mass galaxies, and for the stellar mass functions of low-mass galaxies to be observed at high redshift.

Sheth-Tormen mass function has been widely used to quantify the abundance of dark matter halos. It is a significant improvement over the Press-Schechter mass function as it uses ellipsoidal collapse in place of spherical collapse. Both of these mass functions can be written in a form that is universal, i.e., independent of cosmology and power spectrum when scaled in suitable variables. However, cosmological simulations have shown that this universality is approximate. In this paper, we investigate the power spectrum dependence of halo mass function through a suite of dark-matter-only N-body simulations of seven power-law models in an Einstein-de Sitter cosmology. This choice of cosmology and a power-law power spectrum ensures the self-similar evolution of dark matter distribution, allowing us to isolate the power spectrum dependence of mass function. We find that the mass function shows a clear non-universality. We present fits for the parameters of the Sheth-Tormen mass function for a range of power-law power-spectrum indices. We find a mild evolution in the overall shape of the mass function with the epoch. Finally, we extend our result to LCDM cosmology. We show that the Sheth-Tormen mass function with parameter values derived from a matched power-law EdS cosmology provides a better fit to the LCDM mass function than the standard Sheth-Tormen mass function. Our results indicate that an improved analytical theory is required to provide better fits to the mass function.

We investigate pre-merger coherent radio emission from neutron star mergers arising due to the magnetospheric interaction between compact objects. We consider two plausible radiation mechanisms, and show that if one neutron star has a surface magnetic field $B_{\rm s} \ge 10^{12}$G, coherent millisecond radio bursts with characteristic temporal morphology and inclination angle dependence are observable to Gpc distances with next-generation radio facilities. We explore multi-messenger and multi-wavelength methods of identification of a NS merger origin of radio bursts, such as in fast radio burst surveys, triggered observations of gamma-ray bursts and gravitational wave events, and optical/radio follow-up of fast radio bursts in search of kilonova and radio afterglow emission. We present our findings for current and future observing facilities, and make recommendations for verifying or constraining the model.

The elusive nature of Dark Matter (DM) remains a mystery far from being solved. A vast effort is dedicated to search for signatures of feeble DM interactions with Standard Model particles. In this work, we explore the signatures of axion DM boosted by interactions with Supernova neutrinos: Neutrino-Boosted Axion DM ($\nu$BADM). We focus on $\nu$BADM converting into photons in the Galactic magnetic field, generating a peculiar gamma-ray flux. This signal falls in the poorly explored MeV energy range, that will be probed by next generation gamma-ray missions. Once more, astrophysical searches might act as a probe of fundamental physics, unveiling the nature and properties of DM.

The mechanism to produce the numerous Galactic-Centre filaments (GCF) that vertically penetrate the Galactic plane without clear evidence of connection to the disc remains a mystery . Here we show that the GCFs are explained by relics of supernova remnants (rSNR) driven by hundreds of supernovae (SNe) exploded in the star-forming ring of the central molecular zone (CMZ) at an SN rate of $\sim 2\times 10^{-4}$ y$^{-1}$ in the past $\sim 0.5$ My. The evolution of rSNRs is simulated by the propagation of fast-mode magneto-hydrodynamic (MHD) waves, which are shown to converge around the Galactic rotation axis by the focusing effect. Tangential projection of the cylindrical wave fronts on the sky constitutes the vertical filaments. The SNR model explains not only the morphology, but also the non-thermal radio spectrum, smoothed brightness over the distribution area consistent with the $\Sigma-D$ relation of SNR,and the heating mechanism of hot plasma in the GC. We also discuss the implication of this model on the study of star-formation activity in the central region of the Galaxy.

Like their lower mass siblings, massive protostars can be expected to: a) be surrounded by circumstellar disks and b) launch magnetically-driven jets and outflows. The disk formation and global evolution is thereby controlled by advection of angular momentum from large scales, the efficiency of magnetic braking and the resistivity of the medium, and the internal thermal and magnetic pressures of the disk. We perform a series of 30 simulations of a massive star forming from the gravitational collapse of a molecular cloud threaded by an initially-uniform magnetic field, starting from different values for the mass of the cloud, its initial density and rotation profiles, its rotational energy content, the magnetic field strength, and the resistivity of the material. The gas and dust is modeled with the methods of resistive magnetohydrodynamics, also considering radiation transport of thermal emission and self-gravity. After the initial infall phase dominated by the gravitational collapse, an accretion disk is formed, shortly followed by the launching of magnetically-driven outflows. Two layers can be distinguished in the accretion disk: a thin layer, vertically supported by thermal pressure, and a thick layer, vertically supported by magnetic pressure. We observe the effects of magnetic braking in the inner ~50 au of the disk at late times in our fiducial case. The parameter study reveals that the size of the disk is mostly determined by the density and rotation profiles of the initial mass reservoir and not by the magnetic field strength. Magnetic pressure can slightly increase the size of the accretion disk, while magnetic braking is more relevant in the innermost parts of the disk as opposed to the outer disk. From the parameter study, we infer that multiple initial conditions for the onset of gravitational collapse are able to produce a given disk size and protostellar mass.

We analyse a sunspot simulation in an effort to understand the origin of the convective instabilities giving rise to the penumbral and umbral distinct regimes. We applied the criterion from Gough \& Tayler (1966), accounting for the stabilising effect of the vertical magnetic field to investigate the convective instabilities in a MURaM sunspot simulation. We find: (1) a highly unstable shallow layer right beneath the surface extending all over the simulation box in which convection is triggered by radiative cooling in the photosphere; (2) a deep umbral core (beneath -5 Mm) stabilised against overturning convection that underlies a region with stable background values permeated by slender instabilities coupled to umbral dots; (3) filamentary instabilities below the penumbra nearly parallel to the surface and undulating instabilities coupled to the penumbra which originate in the deep layers. These deep-rooted instabilities result in the vigorous magneto-convection regime characteristic of the penumbra; (4) convective downdrafts in the granulation, penumbra, and umbra develop at about 2 km/s, 1 km/s, and 0.1 km/s, respectively, indicating that the granular regime of convection is more vigorous than the penumbra convection regime which, in turn, is more vigorous than the close-to-steady umbra; (5) the GT criterion outlines both the sunspot magnetopause and peripatopause, highlighting the tripartite nature of the sub-photospheric layers of magnetohydrodynamic (MHD) sunspot models; and, finally, (6) the Jur\v{c}\'ak criterion is the photospheric counterpart of the GT criterion in deep layers. The GT criterion as a diagnostic tool reveals the tripartite nature of sunspot structure with distinct regimes of magneto-convection in the umbra, penumbra, and granulation operating in realistic MHD simulations.

A large dataset of visual magnitudes for all three designs of Starlink satellites is analyzed. Brightness phase functions are derived for the Original, VisorSat and Post-VisorSat models. Similarities and differences between the functions for these spacecraft are noted. A metric called the characteristic magnitude is defined as the average brightness of a satellite when seen overhead at the end of astronomical twilight. When the phase functions are evaluated according to this metric, the characteristic magnitudes are: Original, 4.7; VisorSat, 6.2; and Post-VisorSat, 5.5.

We develop a new process of image plane self-calibration for interferometric imaging data. The process is based on Shape-Orientation-Size (SOS) conservation for the principal triangle in an image generated from the three fringes made from a triad of receiving elements, in situations where interferometric phase errors can be factorized into element-based terms. The basis of the SOS conservation principle is that, for a 3-element array, the only possible image corruption due to an element-based phase screen is a tilt of the aperture plane, leading to a shift in the image plane. Thus, an image made from any 3-element interferometer represents a true image of the source brightness, modulo an unknown translation. Image plane self-calibration entails deriving the unknown translations for each triad image via cross-correlation of the observed triad image with a model image of the source brightness. After correcting for these independent shifts, and summing the aligned triad images, a good image of the source brightness is generated from the full array, recovering source structure at diffraction-limited resolution. The process is iterative, using improved source models based on previous iterations. We demonstrate the technique in the high signal-to-noise context, and include a configuration based on radio astronomical facilities, and simple models of double sources. We show that the process converges for the simple models considered, although convergence is slower than for aperture-plane self-calibration for large-$N$ arrays. As currently implemented, the process is most relevant for arrays with a small number of elements. More generally, the technique provides geometric insight into closure phase and the self-calibration process. The technique is generalizable to non-astronomical interferometric imaging applications across the electromagnetic spectrum.

We explore the presence of self-interacting bosonic dark matter (DM) whithin neutron stars (NSs) in light of the latest mass-radius measurements of the Neutron Star Interior Composition Explorer (NICER). The bosonic DM is distributed in NSs as a core for DM particles with high mass, low fraction and low self-coupling constant or as a halo for particles with low mass, high fraction and high self-coupling constant leading to formation of DM admixed NSs. We focus on the evolution of the visible and dark radius of the mixed object due to DM model parameters and fractions. It is shown that DM core formation reduces the visible radius and total mass pushing them below observational limits while halo formation is in favor of the latest mass-radius constraints. Applying joint constraints for radius of $1.4M_{\odot}$ NSs and the maximum mass from NICER and LIGO/Virgo observations, we scan over the parameter space of the bosonic DM model to obtain an allowed region. It turns out that the maximum mass limit provides a more stringent constraint compare to the radius one. Our investigation allows for the exclusion of a large portion of DM fractions for sub-GeV bosons and limited the amount of accumulated DM to be less than $\sim4\%$ for the entire mass range at the strong coupling regime $\lambda=\pi$. In this paper, we introduce main features of the pulse profile corresponding to the DM admixed NS and the effect of DM halo on the light bending is considered extensively as an independent probe for the DM model. We find that the depth of minimum fluxes in the pulse profiles crucially depend on the amount of DM distributed around NS and its compactness. The current/future astrophysics missions via precise measurements of compact object properties may test the possibility of the existence of DM within NSs and break the degeneracies between different scenarios to interpret exotic observations.

In this work, we want to exploit the magnification bias of the SMGs using two different foreground samples, quasi-stellar objects (QSOs) and galaxies. Our aim is to study and compare their mass density profiles and estimate their masses and concentrations. The background SMG sample consists of objects observed by \textit{Herschel} with 1.2<z<4.0. The foreground samples are QSOs and massive galaxies with spectroscopic redshifts between 0.2 and 1.0. The cross-correlation measurements are estimated with the Davis-Peebles estimator by stacking the SMG-QSO and SMG-galaxy pairs for the two analysed cases, respectively. This approach allows us to study the mass density profile from $\sim2$ to $\sim250$ arcsec. Moreover, the analysis is carried out by combining two of the most common theoretical mass density profiles in order to fit the cross-correlation measurements. The measurements are correctly fitted after splitting the available angular scales into an inner and an outer part using independent mass density profiles for each region. For the QSOs, we obtain masses and concentrations of $\log_{10}(M/M_{\odot})=13.51\pm0.04; C=6.85\pm0.34$ for the inner part and $\log_{10}(M/M_{\odot})=13.44\pm0.17; C=0.36\pm0.18$ for outer parts. For the galaxy sample are $\log_{10}(M/M_{\odot})=13.32\pm0.08; C=8.23\pm0.77$ and $\log_{10}(M/M_{\odot})=12.78\pm0.21; C=1.21\pm1.01$ for the inner and outer parts, respectively. In both samples, the inner part has an excess in the mass density profile and much higher concentration with respect to the outer part. We obtain similar values for the central mass with both samples, in agreement with those of galaxy clusters results. However, the estimated masses for the outer region and the concentrations of the inner region both vary with lens sample. This could be related to the probability of galactic interactions and/or the different evolutionary stages.

Feeding with gas in streams is predicted to be an important galaxy growth mechanism. Using an idealised setup, we study the impact of stream feeding (with 10$^7$ M$_{\odot}$ Myr$^{-1}$ rate) on the star formation and outflows of disc galaxies with $\sim$10$^{11}$ M$_{\odot}$ baryonic mass. The magneto-hydrodynamical simulations are carried out with the PIERNIK code and include star formation, feedback from supernova, and cosmic ray advection and diffusion. We find that stream accretion enhances galactic star formation. Lower angular momentum streams result in more compact discs, higher star formation rates and stronger outflows. In agreement with previous studies, models including cosmic rays launch stronger outflows travelling much further into the galactic halo. Cosmic ray supported outflows are also cooler than supernova only driven outflows. With cosmic rays, the star formation is suppressed and the thermal pressure is reduced. We find evidence for two distinct outflow phases. The warm outflows have high angular momentum and stay close to the galactic disc, while the hot outflow phase has low angular momentum and escapes from the centre deep into the halo. Cosmic rays can therefore have a strong impact on galaxy evolution by removing low angular momentum, possibly metal enriched gas from the disc and injecting it into the circumgalactic medium.

We conduct a systematic search for protocluster candidates at $z \geq 6$ in the COSMOS field using the recently released COSMOS2020 source catalog. We select galaxies using a number of selection criteria to obtain a sample of galaxies that have a high probability of being inside a given redshift bin. We then apply overdensity analysis to the bins using two density estimators, a Weighted Adaptive Kernel Estimator and a Weighted Voronoi Tessellation Estimator. We have found 15 significant ($>4\sigma$) candidate galaxy overdensities across the redshift range $6\le z\le7.7$. The majority of the galaxies appear to be on the galaxy main sequence at their respective epochs. We use multiple stellar-mass-to-halo-mass conversion methods to obtain a range of dark matter halo mass estimates for the overdensities in the range of $\sim10^{11-13}\,M_{\rm \odot}$, at the respective redshifts of the overdensities. The number and the masses of the halos associated with our protocluster candidates are consistent with what is expected from the area of a COSMOS-like survey in a standard $\Lambda$CDM cosmology. Through comparison with simulation, we expect that all the overdensities at $z\simeq6$ will evolve into a Virgo-/Coma-like clusters at present (i.e., with masses $\sim 10^{14}-10^{15}\,M_{\rm \odot}$). Compared to other overdensities identified at $z \geq 6$ via narrow-band selection techniques, the overdensities presented appear to have $\sim10\times$ higher stellar masses and star-formation rates. We compare the evolution in the total star-formation rate and stellar mass content of the protocluster candidates across the redshift range $6\le z\le7.7$ and find agreement with the total average star-formation rate from simulations.

We report the detection of magnesium dicarbide, MgC$_2$, in the laboratory at centimeter wavelengths and assign $^{24}$MgC$_2$, $^{25}$MgC$_2$, and $^{26}$MgC$_2$ to 14 unidentified lines in the radio spectrum of the circumstellar envelope of the evolved carbon star IRC+10216. The structure of MgC$_2$ is found to be T-shaped with a highly ionic bond between the metal atom and the C$_2$ unit, analogous to other dicarbides containing electropositive elements. A two-temperature excitation model of the MgC$_2$ emission lines observed in IRC+10216 yields a very low rotational temperature of $6\pm1$ K, a kinetic temperature of $22\pm13$ K, and a column density of $(1.0 \pm 0.3) \times 10^{12}$ cm$^{-2}$. The abundance of MgC$_2$ relative to the magnesium-carbon chains MgCCH, MgC$_4$H, and MgC$_6$H is $1{:}2{:}22{:}20$ and provides a new constraint on the sequential radiative association-dissociative recombination mechanisms implicated in the production of metal-bearing molecules in circumstellar environments.

We present a Bayesian jackknife test for assessing the probability that a data set contains biased subsets, and, if so, which of the subsets are likely to be biased. The test can be used to assess the presence and likely source of statistical tension between different measurements of the same quantities in an automated manner. Under certain broadly applicable assumptions, the test is analytically tractable. We also provide an open source code, CHIBORG, that performs both analytic and numerical computations of the test on general Gaussian-distributed data. After exploring the information theoretical aspects of the test and its performance with an array of simulations, we apply it to data from the Hydrogen Epoch of Reionization Array (HERA) to assess whether different sub-seasons of observing can justifiably be combined to produce a deeper 21cm power spectrum upper limit. We find that, with a handful of exceptions, the HERA data in question are statistically consistent and this decision is justified. We conclude by pointing out the wide applicability of this test, including to CMB experiments and the $H_0$ tension.

We use in-situ data from the Wind spacecraft to survey the amplitude of turbulent fluctuations in the proton density and total magnetic field inside a large sample of near-Earth magnetic clouds (MCs) associated with coronal mass ejections (CMEs) from the Sun. We find that the most probable value of the modulation index for proton density fluctuations ($\delta n_{p}/n_{p}$) inside MCs ranges from 0.13 to 0.16, while the most probable values for the modulation index of the total magnetic field fluctuations ($\delta B/B$) range from 0.04 to 0.05. We also find that the most probable value of the Mach number fluctuations ($\delta M$) inside MCs is $\approx 0.1$. The anomalous resistivity inside near-Earth MCs arising from electron scattering due to turbulent magnetic field fluctuations exceeds the (commonly used) Spitzer resistivity by a factor of $\approx 500-1000$. The enhanced Joule heating arising from this anomalous resistivity could impact our understanding of the energetics of CME propagation.

In this work, we study whether the engulfment of a brown dwarf (BD) by a solar-like main-sequence (MS) star can significantly alter the structure of the star and the Li content on its surface. We perform 3D Smoothed Particle Hydrodynamics simulations of the engulfment of a BD with masses 0.01 and 0.019 Msun, onto an MS star of 1 Msun and solar composition, in three different scenarios: a head-on collision, a grazing collision, and a merger. We study the dynamics of the interaction in detail, and the relevance of the type of interaction and the mass of the BD on the final fate of the sub-stellar object and the host star in terms of mass loss of the system, angular momentum transfer, and changes in the Li abundance in the surface of the host star. We found that most of the BD mass is diluted in the denser region of the MS star. Only in the merger scenario a significant fraction (40%) of the BD material would remain in the outer layers. We find a clear increase in the surface rotational velocity of the host star after the interaction, ranging between 25 km/s (grazing collision) to 50 km/s (merger). We also find a significant mass loss from the system (1e-4 - 1e-3 Msun) due to the engulfment, which in the case of the merger, may form a circumstellar disk-like structure. Assuming that neither the depth of the convective envelope of the host star nor its mass content are modified during the interaction, a small change in the surface Li abundance in the head-on and grazing collisions is found. However, in the merger we find large Li enhancements, by factors 20-30, depending on the BD mass. Some of these features could be detected observationally in the host star provide they remain long enough time.

Uranus and Neptune exhibit fast surface zonal winds that can reach up to few hundred meters per second. Previous studies on zonal gravitational harmonics and Ohmic dissipation constraints suggest that the wind speeds diminish rapidly in relatively shallow depths within the planets. Through a case-by-case comparison between the missing dynamical gravitational harmonic $J^\prime_4$ from structure models, and with that expected from fluid perturbations, we put constraints on zonal wind decay in Uranus and Neptune. To this end, we generate polytropic empirical structure models of Uranus and Neptune using $4^{\rm th}$-order Theory of Figures (ToF) that leave hydrostatic $J_4$ as an open parameter. Allotting the missing dynamical contribution to density perturbations caused by zonal winds (and their dynamic self-gravity), we find that the maximum scale height of zonal winds are $\sim 2-3\%$ of the planetary radii for both planets. Allowing the models to have $J_2$ solutions in the $\pm 5 \times 10^{-6}$ range around the observed value has similar implications. The effect of self-gravity on $J^\prime_4$ is roughly a factor of ten lower than that of zonal winds, as expected. The decay scale heights are virtually insensitive to the proposed modifications to the bulk rotation periods of Uranus and Neptune in the literature. Additionally, we find that the dynamical density perturbations due to zonal winds have a measurable impact on the shape of the planet, and could potentially be used to infer wind decay and bulk rotation period via future observations.

We present a new planetary global circulation model, planetMPAS, based on the state-of-the-art NCAR MPAS General Circulation Model. Taking advantage of the cross compatibility between WRF and MPAS, planetMPAS includes most of the planetWRF physics parameterization schemes for terrestrial planets such as Mars and Titan. PlanetMPAS also includes a set of physics that represents radiative transfer, dry convection, moist convection and its associated microphysics for the Jovian atmosphere. We demonstrate that, despite the rigid-lid approximation, planetMPAS is suitable to simulate the climate systems in Martian and Jovian atmospheres with potential application to slow-rotating planets such as Titan. Simulations using planetMPAS show that the new model can reproduce many aspects of the observed features on Mars and Jupiter, such as the seasonal CO2 cycle, polar argon enrichment, zonal mean temperature, and qualitative dust opacity on Mars, as well as the equatorial superrotation and banded zonal wind patterns on Jupiter.

We describe the fast transient classification algorithm in the center of the kilonova (KN) science module currently implemented in the Fink broker and report classification results based on simulated catalogs and real data from the ZTF alert stream. We used noiseless, homogeneously sampled simulations to construct a basis of principal components (PCs). All light curves from a more realistic ZTF simulation were written as a linear combination of this basis. The corresponding coefficients were used as features in training a random forest classifier. The same method was applied to long (>30 days) and medium (<30 days) light curves. The latter aimed to simulate the data situation found within the ZTF alert stream. Classification based on long light curves achieved 73.87% precision and 82.19% recall. Medium baseline analysis resulted in 69.30% precision and 69.74% recall, thus confirming the robustness of precision results when limited to 30 days of observations. In both cases, dwarf flares and point Type Ia supernovae were the most frequent contaminants. The final trained model was integrated into the Fink broker and has been distributing fast transients, tagged as \texttt{KN\_candidates}, to the astronomical community, especially through the GRANDMA collaboration. We showed that features specifically designed to grasp different light curve behaviors provide enough information to separate fast (KN-like) from slow (non-KN-like) evolving events. This module represents one crucial link in an intricate chain of infrastructure elements for multi-messenger astronomy which is currently being put in place by the Fink broker team in preparation for the arrival of data from the Vera Rubin Observatory Legacy Survey of Space and Time.

The James Webb Space Telescope's Near Infrared Imager and Slitless Spectrograph (JWST-NIRISS) flies a 7-hole non-redundant mask (NRM), the first such interferometer in space, operating at 3-5 \micron~wavelengths, and a bright limit of $\simeq 4$ magnitudes in W2. We describe the NIRISS Aperture Masking Interferometry (AMI) mode to help potential observers understand its underlying principles, present some sample science cases, explain its operational observing strategies, indicate how AMI proposals can be developed with data simulations, and how AMI data can be analyzed. We also present key results from commissioning AMI. Since the allied Kernel Phase Imaging (KPI) technique benefits from AMI operational strategies, we also cover NIRISS KPI methods and analysis techniques, including a new user-friendly KPI pipeline. The NIRISS KPI bright limit is $\simeq 8$ W2 magnitudes. AMI (and KPI) achieve an inner working angle of $\sim 70$ mas that is well inside the $\sim 400$ mas NIRCam inner working angle for its circular occulter coronagraphs at comparable wavelengths.

Stochastic inflation can resolve strong inflationary perturbations, which seed primordial black holes. I present a fast and accurate way to compute these perturbations in typical black hole producing single-field models, treating the short-wavelength Fourier modes beyond the de Sitter approximation. The squeezing and freezing of the modes reduces the problem to one dimension, and the resulting new form of the stochastic equations, dubbed `constrained stochastic inflation', can be solved efficiently with semi-analytical techniques and numerical importance sampling. In an example case, the perturbation distribution is resolved in seconds deep into its non-Gaussian tail, a speed-up of factor $10^9$ compared to a previous study. Along the way, I comment on the role of the momentum constraint in stochastic inflation.

We carry out three dimensional smoothed particle hydrodynamics simulations to study the impact of planet-disc interactions on a gravitationally unstable protoplanetary disc. We find that the impact of a planet on the disc's evolution can be described by three scenarios. If the planet is sufficiently massive, the spiral wakes generated by the planet dominate the evolution of the disc and gravitational instabilities are completely suppressed. If the planet's mass is too small, then gravitational instabilities are unaffected. If the planet's mass lies between these extremes, gravitational instabilities are weakened. We present mock Atacama Large Millimeter/submillimeter Array (ALMA) continuum observations showing that the observability of large-scale spiral structures is diminished or completely suppressed when the planet is massive enough to influence the disc's evolution. Our results show that massive discs that would be expected to be gravitationally unstable can appear axisymmetric in the presence of a planet. Thus, the absence of observed large-scale spiral structures alone is not enough to place upper limits on the disc's mass, which could have implications on observations of young Class I discs with rings & gaps.

Cosmic voids are promising cosmological laboratories for studying the dark energy phenomenon and alternative gravity theories. They are receiving special attention nowadays in view of the new generation of galaxy spectroscopic surveys, which are covering an unprecedented volume and redshift range. There are two primary statistics in void studies: (i) the void size function, which characterises the abundance of voids, and (ii) the void-galaxy cross-correlation function, which contains information about the density and velocity fields in these regions. However, it is necessary a complete description of the effects of geometrical (Alcock-Paczynski effect, AP) and dynamical (Kaiser effect, RSD) distortions around voids in order to design reliable cosmological tests based on these statistics. Observational measurements show prominent anisotropic patterns that lead to biased cosmological constraints if they are not properly modelled. This thesis addresses this problematic by presenting a theoretical and statistical framework based on dynamical and cosmological foundations capable of describing all the underlying effects involved: the expansion effect (t-RSD), the off-centring effect (v-RSD), the AP-volume effect and the ellipticity effect (e-RSD). These effects can be understood by studying the mapping of voids between real and redshift space. In this way, we lay the foundations for a proper modelling of the aforementioned statistics. In addition, we present a new cosmological test based on two perpendicular projections of the correlation function. The method is fiducial-cosmology free, which allows us to effectively break any possible degeneracy between the cosmological parameters involved. Moreover, it allows us to significantly reduce the number of mock catalogues needed to estimate covariances.

In this follow-up paper, we investigate the use of Convolutional Neural Network for deriving stellar parameters from observed spectra. Using hyperparameters determined previously, we have constructed a Neural Network architecture suitable for the derivation of Teff, log g, [M/H], and vesini. The network was constrained by applying it to databases of AFGK synthetic spectra at different resolutions. Then, parameters of A stars from Polarbase, SOPHIE, and ELODIE databases are derived as well as FGK stars from the Spectroscopic Survey of Stars in the Solar Neighbourhood. The network model average accuracy on the stellar parameters are found to be as low as 80 K for Teff , 0.06 dex for log g, 0.08 dex for [M/H], and 3 km/s for vesini for AFGK stars.

Both stars and planets can lose mass through an expansive wind outflow, often constrained or channeled by magnetic fields that form a surrounding magnetosphere. The very strong winds of massive stars are understood to be driven by line-scattering of the star's radiative momentum, while in the Sun and even lower-mass stars a much weaker mass loss arises from the thermal expansion of a mechanically heated corona. In exoplanets around such low-mass stars, the radiative heating and wind interaction can lead to thermal expansion or mechanical ablation of their atmospheres. Stellar magnetospheres result from the internal trapping of the wind outflow, while planetary magnetospheres are typically shaped by the external impact from the star's wind. But in both cases the stressing can drive magnetic reconnection that results in observable signatures such as X-ray flares and radio outbursts. This review will aim to give an overview of the underlying physics of these processes with emphasis on their similarities and distinctions for stars vs. planets.

Both long and short gamma-ray bursts (GRBs) are expected to occur in the dense environments of active galactic nuclei (AGN) accretion disks. As these bursts propagate through the disks they live in, they photoionize the medium causing time-dependent opacity that results in transients with unique spectral evolution. In this paper we use a line-of-sight radiation transfer code coupling metal and dust evolution to simulate the time-dependent absorption that occurs in the case of both long and short GRBs. Through these simulations, we investigate the parameter space in which dense environments leave a significant and time-variable imprint on the bursts. Our numerical investigation reveals that time dependent spectral evolution is expected for central supermassive black hole masses between $10^5$ and $10^7$ solar masses in the case of long GRBs, and between $10^4$ and $10^7$ solar masses in the case of short GRBs. Our findings can lead to the identification of bursts exploding in AGN disk environments through their unique spectral evolution coupled with a central location. In addition, the study of the time-dependent evolution would allow for studying the disk structure, once the identification with an AGN has been established. Finally, our findings lead to insight into whether GRBs contribute to the AGN emission, and which kind, thus helping to answer the question of whether GRBs can be the cause of some of the as-of-yet unexplained AGN time variability.

We present GRaM-X (General Relativistic accelerated Magnetohydrodynamics on AMReX), a new GPU-accelerated dynamical-spacetime general relativistic magnetohydrodynamics (GRMHD) code which extends the GRMHD capability of Einstein Toolkit to GPU-based exascale systems. GRaM-X supports 3D adaptive mesh refinement (AMR) on GPUs via a new AMR driver for the Einstein Toolkit called CarpetX which in turn leverages AMReX, an AMR library developed for use by the United States DOE's Exascale Computing Project (ECP). We use the Z4c formalism to evolve the equations of GR and the Valencia formulation to evolve the equations of GRMHD. GRaM-X supports both analytic as well as tabulated equations of state. We implement TVD and WENO reconstruction methods as well as the HLLE Riemann solver. We test the accuracy of the code using a range of tests on static spacetime, e.g. 1D MHD shocktubes, the 2D magnetic rotor and a cylindrical explosion, as well as on dynamical spacetimes, i.e. the oscillations of a 3D TOV star. We find excellent agreement with analytic results and results of other codes reported in literature. We also perform scaling tests and find that GRaM-X shows a weak scaling efficiency of $\sim 40-50\%$ on 2304 nodes (13824 NVIDIA V100 GPUs) with respect to single-node performance on OLCF's supercomputer Summit.

Kernel phase imaging (KPI) enables the direct detection of substellar companions and circumstellar dust close to and below the classical (Rayleigh) diffraction limit. We present a kernel phase analysis of JWST NIRISS full pupil images taken during the instrument commissioning and compare the performance to closely related NIRISS aperture masking interferometry (AMI) observations. For this purpose, we develop and make publicly available the custom "Kpi3Pipeline" enabling the extraction of kernel phase observables from JWST images. The extracted observables are saved into a new and versatile kernel phase FITS file (KPFITS) data exchange format. Furthermore, we present our new and publicly available "fouriever" toolkit which can be used to search for companions and derive detection limits from KPI, AMI, and long-baseline interferometry observations while accounting for correlated uncertainties in the model fitting process. Among the four KPI targets that were observed during NIRISS instrument commissioning, we discover a low-contrast (~1:5) close-in (~1 $\lambda/D$) companion candidate around CPD-66~562 and a new high-contrast (~1:170) detection separated by ~1.5 $\lambda/D$ from 2MASS~J062802.01-663738.0. The 5-$\sigma$ companion detection limits around the other two targets reach ~6.5 mag at ~200 mas and ~7 mag at ~400 mas. Comparing these limits to those obtained from the NIRISS AMI commissioning observations, we find that KPI and AMI perform similar in the same amount of observing time. Due to its 5.6 times higher throughput if compared to AMI, KPI is beneficial for observing faint targets and superior to AMI at separations >325 mas. At very small separations (<100 mas) and between ~250-325 mas, AMI slightly outperforms KPI which suffers from increased photon noise from the core and the first Airy ring of the point-spread function.

Metal-poor, star-forming dwarf galaxies produce extreme nebular emission and likely played a major role in cosmic reionization. Yet, determining their contribution to the high-redshift ionizing photon budget is hampered by the lack of observations constraining the ionizing spectra of individual massive stars more metal-poor than the Magellanic Clouds (20-50%$\,Z_\odot$). We present new Keck Cosmic Web Imager (KCWI) optical integral field unit spectroscopy of the only HII region in Leo P (3%$\,Z_\odot$), which is powered by a single O star. We calculate the required production rate of photons capable of ionizing H and He from the observed H$\beta$ and HeI$\,\lambda$4471 emission-line fluxes. Remarkably, we find that the ionizing photon production rate and spectral hardness predicted by a TLUSTY model fit to the stellar SED agrees with our observational measurements within the uncertainties. We then fit Cloudy photoionization models to the full suite of optical emission lines in the KCWI data and show that the shape of the same TLUSTY ionizing continuum simultaneously matches lines across a wide range of ionization energies. Finally, we detect OIII] and NIII] nebular emission in the Hubble Space Telescope far-ultraviolet spectrum of the Leo P HII region, and highlight that the rarely observed NIII] emission cannot be explained by our Cloudy models. These results provide the first observational evidence that widely used, yet purely theoretical, model spectra accurately predict the ionizing photon production rate from late-O stars at very low metallicity, validating their use to model metal-poor galaxies both locally and at high redshift.

As part of the second phase of Advanced Virgo upgrade program, instrumented baffles are being constructed to be installed around the end mirrors in the main arms, in continuation of what has been implemented for the input mode cleaner end mirror during phase I. These baffles will be equipped with photosensors, allowing for real-time monitoring of the stray light around the mirrors. In this paper, we present optical simulations of the light distribution in the detector main cavities to assess the ability of the sensors to effectively monitor misalignment and defects on the mirrors surface and to play a role in the pre-alignment of the interferometer.

A novel instrumented baffle surrounding the suspended end mirror in the input mode cleaner cavity of the Virgo interferometer was installed in spring 2021. Since then, the device has been regularly operated in the experiment and the obtained results indicate a good agreement with simulations of the stray light inside the optical cavity. The baffle will operate in the upcoming O4 observation run, serving as a demonstrator of the technology designed to instrument the baffles in front of the main mirrors in time for O5. In this paper we present a detailed description of the baffle design, including mechanics, front-end electronics, data acquisition, as well as optical and vacuum tests, calibration and installation procedures, and performance results.

Anomaly detection algorithms are typically applied to static, unchanging, data features hand-crafted by the user. But how does a user systematically craft good features for anomalies that have never been seen? Here we couple deep learning with active learning -- in which an Oracle iteratively labels small amounts of data selected algorithmically over a series of rounds -- to automatically and dynamically improve the data features for efficient outlier detection. This approach, AHUNT, shows excellent performance on MNIST, CIFAR10, and Galaxy-DESI data, significantly outperforming both standard anomaly detection and active learning algorithms with static feature spaces. Beyond improved performance, AHUNT also allows the number of anomaly classes to grow organically in response to Oracle's evaluations. Extensive ablation studies explore the impact of Oracle question selection strategy and loss function on performance. We illustrate how the dynamic anomaly class taxonomy represents another step towards fully personalized rankings of different anomaly classes that reflect a user's interests, allowing the algorithm to learn to ignore statistically significant but uninteresting outliers (e.g., noise). This should prove useful in the era of massive astronomical datasets serving diverse sets of users who can only review a tiny subset of the incoming data.

We revisit the viability of the CMSSM, searching for regions of parameter space that yield a neutralino dark matter density compatible with Planck measurements, as well as LHC constraints including sparticle searches and the mass of the Higgs boson, recent direct limits on spin-independent and -dependent dark matter scattering from the LUX-ZEPLIN (LZ) experiment, the indirect constraints from Fermi-LAT and H.E.S.S. on dark matter annihilations to photons in dwarf spheroidal galaxies and the Galactic Centre, and the IceCube limits on muons from annihilations to neutrinos in the Sun. For representative values of $\tan \beta$ and $A_0$ we map in detail the Planck-compatible strips in CMSSM parameter planes, which exhibit multiple distinctive features for large $\tan \beta$, $A_0 = 0$ and $\mu > 0$, and identify portions of the strips that survive all the phenomenological constraints. We find that the most powerful constraint is that from $m_h$, followed by the LZ limit on spin-independent scattering, whereas sparticle searches at the LHC and indirect dark matter searches are less restrictive. Most of the surviving CMSSM parameter space features a Higgsino-like dark matter particle with a mass $\sim 1000-1100$ GeV, which could best be probed with future direct searches for dark matter scattering.

We present the second data release of gravitational waveforms from binary neutron star merger simulations performed by the Computational Relativity (CoRe) collaboration. The current database consists of 254 different binary neutron star configurations and a total of 590 individual numerical-relativity simulations using various grid resolutions. The released waveform data contain the strain and the Weyl curvature multipoles up to $\ell=m=4$. They span a significant portion of the mass, mass-ratio,spin and eccentricity parameter space and include targeted configurations to the events GW170817 and GW190425. CoRe simulations are performed with 18 different equations of state, seven of which are finite temperature models, and three of which account for non-hadronic degrees of freedom. About half of the released data are computed with high-order hydrodynamics schemes for tens of orbits to merger; the other half is computed with advanced microphysics. We showcase a standard waveform error analysis and discuss the accuracy of the database in terms of faithfulness. We present ready-to-use fitting formulas for equation of state-insensitive relations at merger (e.g. merger frequency), luminosity peak, and post-merger spectrum.

Motivated by the fact that the pre-inflationary era may evolve in an exotic way, in this work we formalize anisotropic evolution in the context of modified gravity, focusing on pre-inflationary and near the vicinity of the inflationary epochs. We specialize on specific metrics like Bianchi and Taub and we formalize the inflationary theory in vacuum $F(R)$ gravity, in $F(R)$ gravity with an extra scalar field and in Gauss-Bonnet gravity. We discuss the qualitative effects of the anisotropies on the evolution of the Universe and also we consider several specific solutions, like the de Sitter solution, in both the isotropic and anisotropic contexts. Furthermore, several exotic modified gravity cosmological solutions, like the ones which contain finite time singularities, are also discussed in brief.

In [1], a most general higher curvature non-local gravity action admitting $R^2$-like inflationary solution predicting scalar spectral index $n_s(N)\approx 1-\frac{2}{N}$, where $N$ is the number of e-folds before the end of inflation, $N\gg 1$, any value of the tensor-to-scalar ratio $r(N)<0.036$ and tensor tilt $n_t(N)$ violating the $r= -8n_t$ condition was obtained. In this paper, we compute scalar primordial non-Gaussianities (PNGs) in this theory and effectively demonstrate that higher curvature non-local terms lead to new shapes of reduced bispectrum $f_{\rm NL}\left( k_1,\,k_2,\,k_3 \right)$ mimicking several classes of scalar field models of inflation known in the literature. We obtain $\vert f_{\rm NL}\vert \sim O(1-10)$ in the equilateral, orthogonal, and squeezed limits and the running of PNGs measured by the quantity $\vert\frac{d\ln f_{\rm NL}}{d\ln k}\vert\lesssim 1$. We project these results in the scope of future CMB, Large Scale Structure observations to probe the nature of quantum gravity. Furthermore, we demonstrate that $R^2$-like inflation in non-local modification of gravity brings a paradigm shift in our understanding of early Universe cosmology through non-trivial predictions which go beyond the current status of effective field theories (EFTs) of single field, quasi-single field, and multiple field inflation. In summary, through our generalized non-local $R^2$-like inflation, we obtain for the first time a robust geometric framework of inflation that can explain any detection of observable quantities related to scalar PNGs.

We present the implementation of coupling the EUropean Heliospheric FORcasting Information Asset (EUHFORIA) and the improved Particle Acceleration and Transport in the Heliosphere (iPATH) model and simulate the widespread solar energetic particle (SEP) event of 2020 November 29. We compare the simulated time intensity profiles with measurements at Parker Solar Probe (PSP), the Solar Terrestrial Relations Observatory (STEREO)-A, SOlar and Heliospheric Observatory (SOHO) and Solar Orbiter (SolO). We focus on the influence of the history of shock acceleration on the varying SEP time intensity profiles and investigate the underlying causes in the origin of this widespread SEP event. The temporal evolution of shock parameters and particle fluxes during this event are examined. We find that adopting a realistic solar wind background can significantly impact the expansion of the shock and consequently the shock parameters. Time intensity profiles with an energetic storm particle event at PSP are well reproduced from the simulation. In addition, the simulated and observed time intensity profiles of protons show a similar two-phase enhancement at STA. These results illustrate that modelling a shock using a realistic solar wind is crucial in determining the characteristics of SEP events. The decay phase of the modelled time intensity profiles at Earth agrees well with observations, indicating the importance of perpendicular diffusion in widespread SEP events. Taking into account the possible large curved magnetic field line connecting to SolO, the modelled time intensity profiles show good agreement with the observation. We suggest that the largely distorted magnetic field lines due to a stream interaction region may be a key factor in understanding the observed SEPs at SolO in this event.

In a model of spontaneous scalarization of neutron stars proposed by Damour and Esposite-Farese, a general relativistic branch becomes unstable to trigger tachyonic growth of a scalar field $\phi$ toward a scalarized branch. Applying this scenario to cosmology, there is fatal tachyonic instability of $\phi$ during inflation and matter dominance being incompatible with solar-system constraints on today's field value $\phi_0$. In the presence of a four-point coupling $g^2 \phi^2 \chi^2/2$ between $\phi$ and an inflaton field $\chi$, it was argued by Anson et al. that a positive mass squared heavier than the square of a Hubble expansion rate leads to the exponential suppression of $\phi$ during inflation and that $\phi_0$ can remain small even with the growth of $\phi$ after the radiation-dominated epoch. For several inflaton potentials approximated as $V(\chi)=m^2 \chi^2/2$ about the potential minimum, we study the dynamics of $\phi$ during reheating as well as other cosmological epochs in detail. For certain ranges of the coupling $g$, the homogeneous field $\phi$ can be amplified by parametric resonance during a coherent oscillation of the inflaton. Incorporating the backreaction of created particles under a Hartree approximation, the maximum values of $\phi$ reached during preheating are significantly smaller than those obtained without the backreaction. We also find that the minimum values of $g$ consistent with solar system bounds on $\phi$ at the end of reheating are of order $10^{-5}$ and hence there is a wide range of acceptable values of $g$. Thus, the scenario proposed by Anson et al. naturally leads to the viable cosmological evolution of $\phi$ consistent with local gravity constraints, without modifying the property of scalarized neutron stars.

We model the reported existence of substantive magnetic fields in the vicinity of the central supermassive black holes in Sagitarius A* and Messier 87*, in terms of an axisymmetric, non-rotating Ernst-Melvin-Schwarzschild black hole spacetime with appropriate parameters. We compute the geodesic nodal-plane precession frequency for a test particle with mass, for such a spacetime, and obtain a non-vanishing result, surpassing earlier folklore that only axisymmetric spacetimes with rotation (non-vanishing Kerr parameter) can generate such a precession. We call this magnetic field-generated phenomenon Gravitational Larmor Precession. We discuss observational prospects of this precession in terms of available magnetic field strengths close to central black holes in galaxies.

In this work, we obtain exact thick brane models in $4+1$ dimensions generated by higher order field theory kinks, inspired by specific potentials for $\phi^{10}$ and $\phi^{18}$ models. We verify that the geodesic equation along the fifth dimension confirms the confining effects of the scalar field on the brane for all of these models. These models provide new solutions with exponential and power-law tails which live in different topological sectors. We show that the resulting branes of specific exponential law models do not possess $Z_2$-symmetry. Furthermore, we examine the stability of the thick branes, by determining the sign of the $w^2$ term in the expansion of the potential for the resulting Schr\"{o}dinger-like equation. It turns out that two of the three models of the $\phi^{10}$ brane are stable, while another contains unstable modes for certain ranges of the model parameters. We also show that the brane solution from the specific $\phi^{18}$ models are stable, while the others involve neutral equilibrium. The asymptotic behaviour of the brane solutions are also discussed.

We present a method to search for scalar field ultralight dark matter directly interacting with gravitational-wave interferometers via a modulation of the fine structure constant and the electron mass. This modulation induces an effective strain in solid materials at a frequency determined by the mass of the dark matter particle. We study the prospects for looking for such an effect in the LIGO detectors by using the solid cavity which is nominally used for pre-stabilizing the laser frequency and we project upper limits. We contextualize them with previous limits from GEO600, possible limits from a similar strain in the LIGO beamsplitter, and with potential limits from upcoming experiments like LISA, Cosmic Explorer and from an upgraded solid cavity. We find that with the sensitivity of Advanced LIGO, competitive upper limits on DM coupling can be placed at the level of $\left\vert d_{m_e}+d_e\right\vert \sim 0.2$ for $m_\text{DM} \sim 10^{-13}\,\mathrm{eV}/\mathrm{c}^2$ with a combination of two searches using the solid cavity and the beamsplitter in LIGO; future experiments could reduce this upper limit to $\sim10^{-3}$.