Papers for Tuesday, Jan 10 2023

The microphysical, kinetic properties of astrophysical plasmas near accreting compact objects are still poorly understood. For instance, in modern general-relativistic magnetohydrodynamic simulations, the relation between the temperature of electrons $T_{e}$ and protons $T_{p}$ is prescribed in terms of simplified phenomenological models where the electron temperature is related to the proton temperature in terms of the ratio between the gas and magnetic pressures, or $\beta$ parameter. We here present a very comprehensive campaign of {two-dimensional} kinetic Particle-In-Cell (PIC) simulations of special-relativistic turbulence to investigate systematically the microphysical properties of the plasma in the trans-relativistic regime. Using a realistic mass ratio between electrons and protons, we analyze how the index of the electron energy distributions $\kappa$, the efficiency of nonthermal particle production $\mathcal{E}$, and the temperature ratio $\mathcal{T}:=T_{e}/T_{p}$, vary over a wide range of values of $\beta$ and $\sigma$. For each of these quantities, we provide two-dimensional fitting functions that describe their behaviour in the relevant space of parameters, thus connecting the microphysical properties of the plasma, $\kappa$, $\mathcal{E}$, and $\mathcal{T}$, with the macrophysical ones $\beta$ and $\sigma$. In this way, our results can find application in wide range of astrophysical scenarios, including the accretion and the jet emission onto supermassive black holes, such as M87* and Sgr A*.

DR Tau has been noted for its unusually high variability in comparison with other T Tauri stars. Although it is one of the most extensively studied pre-main sequence stars, observations with millimeter interferometry have so far been relatively limited. We present NOEMA images of $^{12}$CO, $^{13}$CO, C$^{18}$O, SO, DCO$^+$, and H$_2$CO toward DR Tau at a resolution of $\sim0.5''$ ($\sim100$ au). In addition to the protoplanetary disk, CO emission reveals an envelope, a faint asymmetric outflow, and a spiral arm with a clump. The $\sim1200$ au extent of the CO arm far exceeds that of the spiral arms previously detected in scattered light, which underlines the necessity of sensitive molecular imaging for contextualizing the disk environment. The kinematics and compact emission distribution of C$^{18}$O, SO, DCO$^+$, and H$_2$CO indicate that they originate primarily from within the Keplerian circumstellar disk. The SO emission, though, also exhibits an asymmetry that may be due to interaction with infalling material or unresolved substructure. The complex environment of DR Tau is reminiscent of those of outbursting FUor sources and some EXor sources, suggesting that DR Tau's extreme stellar activity could likewise be linked to disk instabilities promoted by large-scale infall.

Using 190,000 spectra from the seventeenth data release of the Sloan Digital Sky Survey, we investigate the ultraviolet emission line properties in z=2 quasars. Specifically, we quantify how the shape of CIV 1549A and the equivalent width (EW) of HeII 1640A depend on the black hole mass and Eddington ratio inferred from MgII 2800A. Above L/L_Edd>0.2, there is a strong mass dependence in both CIV blueshift and HeII EW. Large CIV blueshifts are observed only in regions with both high mass and high accretion rate. Including X-ray measurements for a subsample of 5,300 objects, we interpret our observations in the context of AGN accretion and outflow mechanisms. The observed trends in HeII and 2 keV strength are broadly consistent with theoretical QSOSED models of AGN spectral energy distributions (SEDs) for low spin black holes, where the ionizing SED depends on the accretion disc temperature and the strength of the soft excess. High spin models are not consistent with observations, suggesting SDSS quasars at z=2 may in general have low spins. We find a dramatic switch in behaviour at L/L_Edd<0.2: the ultraviolet emission properties show much weaker trends, and no longer agree with QSOSED predictions, hinting at changes in the structure of the broad line region. Overall the observed emission line trends are generally consistent with predictions for radiation line driving where quasar outflows are governed by the SED, which itself results from the accretion flow and hence depends on both the SMBH mass and accretion rate.

Around 400 million years after the big bang, ultraviolet emission (Lyman Continuum, LyC) from star-forming galaxies drove the reionization of the Universe. How this radiation escapes the cold neutral gas (HI) of galaxies with sufficiently little absorption to reionize the intergalactic medium is poorly understood. HI has never been mapped in confirmed LyC-emitters, leaving major uncertainties on how LyC photons escape galaxies and ionize the intergalactic medium. We imaged the 21cm HI emission of nearby reionization-era analog galaxy Haro 11 to identify how ionizing radiation escapes the neutral interstellar medium. We find that merger-driven interactions have tidally displaced up to 82% of the neutral gas from the ultraviolet emission production sites in the galaxy, allowing the escape of ionizing radiation to the intergalactic medium. Increased galaxy interactions in the early Universe predicted by cosmological models could contribute significantly to the reionization of the Universe.

SMSS J160540.18$-$144323.1 is the carbon-enhanced metal-poor (CEMP) star with the lowest iron abundance ever measured, [Fe/H]=-6.2, which was first reported with the SkyMapper telescope. The carbon abundance is A(C)~6.1 in the low-C band, as the majority of the stars in this metallicity range. Yet, constraining the isotopic ratio of key species, such as carbon, sheds light on the properties and origin of these elusive stars. We performed high-resolution observations of SMSS1605$-$1443 with the ESPRESSO spectrograph to look for variations in the radial velocity ($v_{rad}$) with time. These data have been combined with older MIKE and UVES archival observations to enlarge the temporal baseline. The $^{12}$C/$^{13}$C isotopic ratio is also studied to explore the possibility of mass transfer from a binary companion. A cross-correlation function against a natural template was applied to detect $v_{rad}$ variability and a spectral synthesis technique was used to derive $^{12}$C/$^{13}$C in the stellar atmosphere. We confirm previous indications of binarity in SMSS1605$-$1443 and measured a lower limit $^{12}$C/$^{13}$C$>60$ at more than a 3$\sigma$ confidence level, proving that this system is chemically unmixed and that no mass transfer from the unseen companion has happened so far. Thus, we confirm the CEMP-no nature of SMSS1605$-$1443 and show that the pristine chemical composition of the cloud from which it formed is currently imprinted in its stellar atmosphere free of contamination.

Layers of ionized plasma, in the form of winds ejected from the accretion disk of Supermassive Black Holes (SMBHs) are frequently observed in Active Galactic Nuclei (AGNs). Winds with a velocity often exceeding $0.1c$ are called Ultra-Fast-Outflows (UFOs) and thanks to their high power they can play a key role in the co-evolution between the SMBH and the host galaxy. In order to construct a proper model of the properties of these winds, it is necessary to consider special relativistic corrections due to their very high velocities. We present a derivation of the Poynting-Robertson effect (P-R effect) and apply it to the description of the dynamics of UFOs. The P-R effect is a special relativistic correction which breaks the isotropy of the radiation emitted by a moving particle funneling the radiation in the direction of motion. As a result of the conservation of the four-momentum, the emitting particles are subjected to a drag force and decelerate. We provide a derivation of the drag force caused by the P-R effect starting from general Lorentz transformations and assuming isotropic emission in the gas reference frame. Then, we derive the equations to easily implement this drag force in future simulations. Finally, we apply them in a toy model in which the gas particles move radially under the influence of the gravitation force, the radiation pressure and the drag due to the P-R effect. P-R effect plays an important role in determining the velocity profile of the wind. For a wind launched from $r_0=10r_s$ (where $r_S$ stands for the Schwarzschild radius), the asymptotic velocity reached by the wind is between $10$% and $24$% smaller than the one it would possess if we neglect the effect. This shows that the P-R effect should be taken into account when studying the dynamics of high-velocity, photoionized outflows in general.

Understanding the origins of ultrahigh energy cosmic rays (UHECRs) - which reach energies in excess of $10^{20}~{\rm eV}$ - stretches particle acceleration physics to its very limits. In this review, we discuss how such energies can be reached, using general arguments that can often be derived on the back of an envelope. We explore possible particle acceleration mechanisms, with special attention paid to shock acceleration. Informed by the arguments derived, we discuss where UHECRs might come from and which classes of powerful astrophysical objects could be UHECR sources; generally, we favour radio galaxies, GRB afterglows and other sources which are not too compact and dissipate prodigious amounts of energy on large scales, allowing them to generate large products $\beta B R$ without the CRs undergoing restrictive losses. Finally, we discuss when UHECRs are accelerated by highlighting the importance of source variability, and explore the intriguing possibility that the UHECR arrival directions are partly a result of "echoes" from magnetic structures in the local Universe.

We present the Rhapsody-C simulations that extend the Rhapsody-G suite of massive galaxy clusters at the $M_{\rm vir}\sim10^{15}\thinspace{\rm M}_{\odot}$ scale with cosmological magneto-hydrodynamic zoom-in simulations that include anisotropic thermal conduction, modified supermassive black hole (SMBH) feedback, new SMBH seeding and SMBH orbital decay model. These modelling improvements have a dramatic effect on the SMBH growth, star formation and gas depletion in the proto-clusters. We explore the parameter space of the models and report their effect on both star formation and the thermodynamics of the intra-cluster medium (ICM) as observed in X-ray and SZ observations. We report that the star formation in proto-clusters is strongly impacted by the choice of the SMBH seeding as well as the orbital decay of SMBHs. Feedback from AGNs is substantially boosted by the SMBH decay, its time evolution and impact range differ noticeably depending on the AGN energy injection scheme used. Compared to a mass-weighted injection whose energy remains confined close to the central SMBHs, a volume-weighted thermal energy deposition allows to heat the ICM out to large radii which severely quenches the star formation in proto-clusters. By flattening out temperature gradients in the ICM, anisotropic thermal conduction can reduce star formation early on but weakens and delays the AGN activity. Despite the dissimilarities found in the stellar and gaseous content of our haloes, the cluster scaling relations we report are surprisingly insensitive to the subresolution models used and are in good agreement with recent observational and numerical studies.

Filament finders are limited, among other things, by the abundance of spectroscopic redshift data. As there are proportionally more photometric redshift data than spectroscopic, we aim to use photometric data to improve and expand the areas where we can detect the large-scale structure of the Universe. We present a proof of concept, showing that the Bisous filament finder can improve the detected filamentary network with photometric redshift data. We created mock data from the MultiDark-Galaxies catalogue. Galaxies with spectroscopic redshifts were given exact positions from the simulation. Galaxies with photometric redshifts were given uncertainties along one coordinate. The errors were generated with different Gaussian distributions for different samples. There are three different types of samples: spectroscopic only, photometric only, and mixed samples of galaxies with photometric and spectroscopic redshifts. In photometric-only samples, the larger the uncertainty for photometric redshifts, the fewer filaments are detected, and the filaments strongly align along the line of sight. Using mixed samples improves the number of filaments detected and decreases the alignment bias of those filaments. The results are compared against the full spectroscopic sample. The recall for photometric-only samples depends heavily on the size of uncertainty and dropped close to 20%; for mixed samples, the recall stayed between 40% and 80%. The false discovery rate stayed below 5% in every sample tested in this work. Mixed samples showed better results than corresponding photometric-only or spectroscopic-only samples for every uncertainty size and number of spectroscopic galaxies in mixed samples. Mixed samples of galaxies with photometric and spectroscopic redshifts help us to improve and extend the large-scale structure further than possible with only spectroscopic samples.

The Haystack Telescope is an antenna with a diameter of 37~m and an elevation-dependent surface accuracy of $\le{}100~\mu{}\rm{}m$ that is capable of millimeter-wave observations. The radome-enclosed instrument serves as a radar sensor for space situational awareness, with about one-third of the time available for research by MIT Haystack Observatory. Ongoing testing with the K-band (18-26~GHz) and W-band receivers (currently 85-93~GHz) is preparing the inclusion of the telescope into the Event Horizon Telescope (EHT) array and the use as a single-dish research telescope. Given its geographic location, the addition of the Haystack Telescope to current and future versions of the EHT array would substantially improve the image quality.

We combine datasets from the CGM$^{2}$ and CASBaH surveys to model a transition point, $R_{\rm cross}$, between circumgalactic and intergalactic media (CGM and IGM, respectively). In total, our data consist of 7244 galaxies at z < 0.5 with precisely measured spectroscopic redshifts, all having impact parameters of 0.01 - 20 comoving Mpc from 28 QSO sightlines with high-resolution UV spectra that cover H I Ly$\alpha$. Our best-fitting model is an exclusionary two-component model that combines a 3D absorber-galaxy cross correlation function with a simple Gaussian profile at inner radii to represent the CGM. By design, this model gives rise to a determination of $R_{\rm cross}$ as a function of galaxy stellar mass, which can be interpreted as the boundary between the CGM and IGM. For galaxies with $10^8 \leq M_{\star}/M_{\odot} \leq 10^{10.5}$, we find that $R_{\rm cross}(M_{\star}) \approx 2 \pm 0.6 R_{\rm vir}$. Additionally, we find excellent agreement between $R_{\rm cross}(M_{\star})$ and the theoretically-determined splashback radius for galaxies in this mass range. Overall, our results favor models of galaxy evolution at z < 0.5 that distribute $T \approx 10^{4}$K gas to distances beyond the virial radius.

The "cosmic web", the filamentary large-scale structure in a cold dark matter Universe, is readily apparent via galaxy tracers in spectroscopic surveys. However, the underlying dark matter structure is as of yet unobservable and mapping the diffuse gas permeating it lies beyond practical observational capabilities. A recently developed technique, inspired by the growth and movement of Physarum polycephalum "slime mold", has been used to map the cosmic web of a low redshift sub-sample of the SDSS spectroscopic galaxy catalog. This model, the Monte Carlo Physarum Machine (MCPM) was shown to promisingly reconstruct the cosmic web. Here, we improve the formalism used in calibrating the MCPM to better recreate the Bolshoi-Planck cosmological simulation's density distributions and apply them to a significantly larger cosmological volume than previous works using the Sloan Digital Sky Survey (SDSS, $z < 0.1$) and the Extended Baryon Oscillation Spectroscopic Survey (eBOSS) Luminous Red Galaxy (LRG, $z \lesssim 0.5$) spectroscopic catalogs. We present the "Cosmic Slime Value Added Catalog" which provides estimates for the cosmic overdensity for the sample of galaxies probed spectroscopically by the above SDSS surveys. In addition, we provide the fully reconstructed 3D density cubes of these volumes. These data products were released as part of Sloan Digital Sky Survey Data Release 17 and are publicly available. We present the input catalogs and the methodology for constructing these data products. We also highlight exciting potential applications to galaxy evolution, cosmology, the intergalactic and circumgalactic medium, and transient phenomenon localization.

The strongest known correspondence between ALMA 3mm emission and other solar observations is between the H-alpha line width and 3 mm brightness temperature, while the typical 3-5min p-mode oscillations found in many chromospheric diagnostics are often lacking from ALMA Band 3 and 6 observations. We study these issues using a publicly available data set of weak network flux near disk center at time SOL2017-03-17T15:42-16:45 that includes IBIS H-alpha and ALMA 3 mm data series. We confirm the correlation between the H-alpha line width and the 3 mm temperature, but find a different slope between the two diagnostics for hot versus cool regions, both of which are steeper than previous reports. The origin of the two slopes is unknown, but does hold for the duration of the observations. Spatially averaged power spectra of the IBIS data do show p-mode oscillations while the ALMA data do not. However, removing IBIS data at times corresponding to the ALMA calibration windows makes the averaged power spectra for the two data series nearly identical. Spatial maps of the power integrated over p-mode frequency bands agree well between the two data series and show the typical pattern of magnetic shadows and halos found in many chromospheric diagnostics. We therefore argue that the lack of observed p-modes in the ALMA data may be predominantly due to spectral windowing induced by the timing and duration of the calibration observations.

JWST has begun its scientific mission, which includes the atmospheric characterization of transiting exoplanets. Some of the first exoplanets to be observed by JWST have equilibrium temperatures below 1000 K, which is a regime where photochemical hazes are expected to form. The optical properties of these hazes, which controls how they interact with light, are critical for interpreting exoplanet observations, but relevant data are not available. Here we measure the optical properties of organic haze analogues generated in water-rich exoplanet atmosphere experiments. We report optical constants (0.4 to 28.6 micron) of organic hazes for current and future observational and modeling efforts covering the entire wavelength range of JWST instrumentation and a large part of Hubble. We use these optical constants to generate hazy model atmospheric spectra. The synthetic spectra show that differences in haze optical constants have a detectable effect on the spectra, impacting our interpretation of exoplanet observations. This study emphasizes the need to investigate the optical properties of hazes formed in different exoplanet atmospheres, and establishes a practical procedure to determine such properties.

It has been well established in the local universe that galaxy properties differ based on the large-scale environment in which they reside. As luminous Lyman-alpha nebulae have been shown to trace overdense environments at z~2-3, comparing the properties of galaxies within Lyman-alpha nebulae systems to those in the field can provide insight into how and when locally-observed trends between galaxy properties and environment emerged. Six Lyman-alpha nebulae were discovered at z~2.3 in a blind search of the GOODS-S extragalactic field, a region also covered by the 3D-HST spectroscopic survey. Utilizing 3D-HST data, we identified 86 galaxies in the vicinity of these nebulae and used statistical tests to compare their physical properties to galaxies elsewhere in the field. Galaxies lying within 320 proper kpc of a Lyman-alpha nebula are roughly half a magnitude brighter than those in the field, with higher stellar masses, higher star formation rates, and larger effective radii. Even when considering the effects of sample incompleteness, our study suggests that galaxies in overdensities at z~2.3 traced by Lyman-alpha nebulae are being influenced by their environment. Furthermore, Lyman-alpha nebula-associated galaxies lie on the same main sequence of star formation as field galaxies, but have a larger proportion of high-mass galaxies, consistent with the idea that galaxy evolution is accelerated in rich environments. Expanded surveys for Lyman-alpha nebulae in other deep extragalactic fields and galaxy spectroscopic follow-up with JWST will better constrain the demographics of Lyman-alpha nebula-associated galaxies.

The last 22.5 orbits of the Cassini mission brought the spacecraft to less than 3000 km from Saturn's 1-bar surface. These close encounters offered an unprecedented view of Saturn's magnetic field, including contributions from the internal dynamo, the ionosphere, and the magnetosphere. In this chapter, we highlight the new picture of Saturn's magnetic field from the Cassini mission including the persistent yet time-varying low-latitude field-aligned currents, Alfv\'en waves planet-ward of the D-ring, extreme axisymmetry, and high-degree magnetic moments. We then discuss the implications and new questions raised for Saturn's innermost magnetosphere, equatorial ionosphere, and interior. We conclude this chapter with an outlook for the future exploration of Saturn and other giant planets.

Planetary nebulae (PNe), the ejected envelopes of red giant stars, provide us with a history of the last, mass-losing phases of 90 percent of stars initially more massive than the Sun. Here, we analyse James Webb Space Telescope (JWST) Early Release Observation (ERO) images of the PN NGC3132. A structured, extended H2 halo surrounding an ionised central bubble is imprinted with spiral structures, likely shaped by a low-mass companion orbiting the central star at 40-60 AU. The images also reveal a mid-IR excess at the central star interpreted as a dusty disk, indicative of an interaction with another, closer companion. Including the previously known, A-type visual companion, the progenitor of the NGC3132 PN must have been at least a stellar quartet. The JWST images allow us to generate a model of the illumination, ionisation and hydrodynamics of the molecular halo, demonstrating the power of JWST to investigate complex stellar outflows. Further, new measurements of the A-type visual companion allow us to derive the value for the mass of the progenitor of a central star to date with excellent precision: 2.86+/-0.06 Mo. These results serve as path finders for future JWST observations of PNe providing unique insight into fundamental astrophysical processes including colliding winds, and binary star interactions, with implications for supernovae and gravitational wave systems.

We study the choked accretion process of an ultrarelativistic fluid onto axisymmetric Kerr-Sen black holes in Einstein-Maxwell-dilation-axion theory. Based on solving procedure mentioned by Petrich, Shapiro,and Teukolsky, we further calculate the solution describing the velocity potential {\Phi} of a stationary, irrotational fluid, which satisfies the stiff equation of state. Then, by using the ZAMO framework, we draw the streamlined diagram of the quadrupolar flow solution and investigate how parameters affect the solution's coefficient and stagnation point. The injection rate, ejection rate, and critical angle are discussed in detail at the end of the article.

The James Webb Space Telescope Time-Domain Field (JWST-TDF) is an $\sim$14$'$ diameter field near the North Ecliptic Pole that will be targeted by one of the JWST Guaranteed Time Observations programs. Here, we describe our James Clerk Maxwell Telescope SCUBA-2 850 $\mu$m imaging of the JWST-TDF and present the submillimeter source catalog and properties. We also present a catalog of radio sources from Karl J. Jansky Very Large Array 3 GHz observations of the field. These observations were obtained to aid JWST's study of the dust-obscured galaxies that contribute significantly to the cosmic star formation at high redshifts. Our deep 850 $\mu$m map covers the JWST TDF at a noise level of $\sigma_{850}$ = 1.0 mJy beam$^{-1}$, detecting 83/31 sources in the main/supplementary signal-to-noise ratio (S/N $>$ 4 / S/N = 3.5 - 4) sample respectively. The 3 GHz observations cover a 24$'$ diameter field with a 1 $\sigma$ noise of 1$\mu$Jy beam$^{-1}$ at a 0$.\!\!^{\prime\prime}$7 FWHM. We identified eighty-five 3 GHz counterparts to sixty-six 850 $\mu$m sources and then matched these with multiwavelength data from the optical to the mid-infrared wave bands. We performed spectral energy distribution fitting for 61 submillimeter galaxies (SMGs) matched with optical/near-infrared data, and found that SMGs at S/N $>$ 4 have a median value of $z_{phot} = $2.22 $\pm$ 0.12, star formation rates of 300 $\pm$ 40 M$_{\odot}\,{\rm yr^{-1}}$ (Chabrier initial mass function), and typical cold dust masses of 5.9 $\pm$ 0.7 $ \times$ 10$^{8} $M$_{\odot}$, in line with bright SMGs from other surveys. The large cold dust masses indicate correspondingly large cool gas masses, which we suggest are a key factor necessary to drive the high star formation rates seen in this population

New developments in data processing and visualization are being made in preparation for upcoming radioastronomical surveys planned with the Square Kilometre Array (SKA) and its precursors. A major goal is enabling extraction of science information from the data in a mostly automated way, possibly exploiting the capabilities offered by modern computing infrastructures and technologies. In this context, the integration of source analysis algorithms into data visualization tools is expected to significantly improve and speed up the cataloguing process of large area surveys. To this aim, the CIRASA (Collaborative and Integrated platform for Radio Astronomical Source Analysis) project was recently started to develop and integrate a set of services for source extraction, classification and analysis into the ViaLactea visual analytic platform and knowledge base archive. In this contribution, we will present the project objectives and tools that have been developed, interfaced and deployed so far on the prototype European Open Science Cloud (EOSC) infrastructure provided by the H2020 NEANIAS project.

Some accretion powered X-ray pulsars with supergiant companion stars undergo occasional rapid spin-up episodes that last for weeks to a few months. We explore the changes in the accretion environment of the pulsar GX 301-2 during its latest 80 days long spin-up episode in 2019 when the spin frequency of the pulsar increased by ~2% over two orbits of the binary. By performing time-resolved spectroscopy with the MAXI/GSC spectra of the source, we estimated the equivalent hydrogen column density and equivalent width of the iron fluorescence line during the spin-up episode, and compared them with the long-term average values estimated by orbital-phase resolved spectroscopy. The measured absorption column density during the spin-up episode is about twice that of an average orbit, while the equivalent width of the iron line is less than half of an average orbit. Though the spin-up episode started immediately after a pre-periastron flare and lasted for the two consecutive orbits of the binary, the associated enhancement in luminosity started a few days after the pre-periastron flare and lasted only during the first orbit, and some enhancement was seen again during the pre-periastron passage of the second orbit. The absorption column density and iron line equivalent width vary throughout the spin-up episode and are distinct from an average orbit. These observations indicate a significant change in the accretion and reprocessing environment in GX 301-2 during the spin-up episode and may hold important clues for the phenomenon in this source and several other sources with supergiant companions.

The escape fraction of Lyman continuum (LyC) photons ($f_{esc}$) is a key parameter for determining the sources of cosmic reionization at $z\geq 6$. At these redshifts, owing to the opacity of the intergalactic medium, LyC emission cannot be measured directly. However LyC leakers during the epoch of reionization could be identified using indirect indicators, that have been extensively tested at low and intermediate redshift. These include a high [OIII]/[OII] flux ratio, a high star formation surface density and a compact size. In this work we present observations of 29 $4.5 \leq z \leq 8$ gravitationally lensed galaxies in the Abell 2744 cluster field. From a combined analysis of JWST-NIRSpec and NIRCam data we accurately derive their physical and spectroscopic properties: our galaxies have low masses $(\log(M_\star)\sim 8.5)$, blue UV spectral slopes ($\beta \sim -2.1$), compact sizes ($r_e \sim 0.3-0.5$ kpc), and high [OIII]/[OII] flux ratios. Such properties are similar to those of low-redshift LyC leakers. Indirectly inferring the fraction of escaping ionizing photons, we find that more than 80\% of our galaxies have predicted $f_{esc}$ larger than 0.05, i.e. they would be considered leakers. The average predicted $f_{esc}$ of our sample is 0.12, suggesting that similar galaxies at $z\geq 6$ provided a substantial contribution to cosmic reionization.

Gravitational waves (GWs) from tens of millions of compact binaries in our Milky Way enter the milli-Hertz band of space-based detection. The majority of them cannot be resolved individually, resulting in a foreground confusion noise for Laser Interferometer Space Antenna (LISA). The concept of Taiji mission is similar to LISA's with slightly better sensitivity, which means that the galactic GW signals will also affect the detection with Taiji. Here we generate the GW signals from 29.8 million galactic binaries for Taiji and subtract the `resolvable' sources. The confusion noise is estimated and fitted in an analytic form with 6-month, 1-year, 2-year and 4-year observation time. We find that the full sensitivity curve is slightly lower for Taiji than for LISA at frequencies of $\leq 0.8$ mHz and around 2~mHz. For a 4-year lifetime, more than 29 thousand sources are resolvable with Taiji. Compared to LISA, Taiji can subtract $\sim 20 \%$ more sources and the distribution of them in our Milky Way is consistent with that of the resolvable sources with LISA.

We present Karl G. Jansky Very Large Array (VLA) K-band (19 GHz) observations of the redshifted CO(1-0) line emission toward the radio galaxy TN J0924$-$2201 at $z=5.2$, which is one of the most distant CO-detected radio galaxies. With the angular resolution of $\sim2''$, the CO(1-0) line emission is resolved into three clumps, within $\pm500$ km\,s$^{-1}$ relative to its redshift, where is determined by Ly$\alpha$. We find that they locate off-center and 12-33 kpc away from the center of the host galaxy, which has counterparts in $HST$ $i$-band, $Spitzer$/IRAC and ALMA Band-6 (230 GHz; 1.3 mm). With the ALMA detection, we estimate $L_{\rm IR}$ and SFR of the host galaxy to be $(9.3\pm1.7)\times10^{11} L_{\odot}$ and $110\pm20$ $M_{\odot}\,\rm yr^{-1}$, respectively. We also derive the $3\sigma$ upper limit of $M_{\rm H_{2}}<1.3\times10^{10}$ $M_{\odot}$ at the host galaxy. The detected CO(1-0) line luminosities of three clumps, $L'_{\rm CO(1-0)}$ = (3.2-4.7)$\times10^{10}$ $\rm\,K\,km\,s^{-1}pc^{2}$, indicate the presence of three massive molecular gas reservoirs with $M_{\rm H_{2}}$ = (2.5-3.7)$\times10^{10}$ $M_{\odot}$, by assuming the CO-to-H$_{2}$ conversion factor $\alpha_{\rm CO} = 0.8$ $M_{\rm \odot}\rm\,(K\,km\,s^{-1}pc^{2})^{-1}$, although the star formation rate (SFR) is not elevated because of the non-detection of ALMA 1.3 mm continuum (SFR $<$ 40 $M_\odot$ yr$^{-1}$). From the host galaxy, the nearest molecular gas clump labeled as clump A, is apparently aligning with the radio jet axis, showing the radio-CO alignment. The possible origin of these three clumps around TN J0924$-$2201 can be interpreted as merger, jet-induced metal enrichment and outflow.

It has recently been reported that the application of convolutional neural-network techniques to infer the dark-matter distribution in the local cosmos has revealed how it follows the $D\approx 2$ hierarchical distribution of galaxies in the locality, rather than exhibiting the expected homogeneity throughout the IGM. Taken at face value, this implies that the Hubble Law, observed to be followed on scales which are deep inside the observed hierarchical structures, can no longer be assumed to arise from universal expansion. So, if not universal expansion, then what? As a possibility, it has been recognized for a considerable time that if the lower cut-off scales of a $D \approx 2$ hierarchical cosmos are identified with the scales of a typical galaxy, then gravitational redshift automatically follows the Hubble Law with $H_g \approx 70\,km/sec/Mpc$. Inter alia, this suggests a model of galaxy formation in a $D\approx2$ hierarchical IGM in which all of the material $M_0$ within a sphere $R_0$ coalesces about a unique center so that hierarchical symmetry is broken on the scale $(M_0,R_0)$. Putting these things together leads unambiguously to the conclusion that, in an hierachical cosmos, the Dark Matter hypothesis and Milgrom's MOND hypothesis are two sides of the same coin.

Short gamma-ray bursts are associated with binary neutron star mergers, which are multimessenger astronomical events that have been observed both in gravitational waves and in the multiband electromagnetic spectrum. Depending on the masses of the stars in the binary and on details of their largely unknown equation of state, a dynamically evolving and short-lived neutron star may be formed after the merger, existing for approximately 10-300 ms before collapsing to a black hole. Numerical relativity simulations across different groups consistently show broad power spectral features in the 1-5 kHz range in the post-merger gravitational wave signal, which is inaccessible by current gravitational-wave detectors but could be seen by future third generation ground-based detectors in the next decade. This implies the possibility of quasiperiodic modulation of the emitted gamma-rays in a subset of events where a neutron star is formed shortly prior to the final collapse to a black hole. Here we present two such signals identified in the short bursts GRB 910711 and GRB 931101B from archival BATSE data, which are compatible with the predictions from numerical relativity.

Sunquakes are enhanced seismic waves excited in some energetic solar flares. Up to now, their origin has still been controversial. In this Letter, we select and study 20 strong flares in Solar Cycle 24, whose impulse phase is fully captured by the \emph{Reuven Ramaty High Energy Solar Spectroscopic Imager} (\emph{RHESSI}). For 11 out of 12 sunquake-active flares in our sample, the hard X-ray (HXR) emission shows a good temporal and spatial correlation with the white-light (WL) enhancement and the sunquake. Spectral analysis also reveals a harder photon spectrum that extends to several hundred keV, implying a considerable population of flare-accelerated nonthermal electrons at high energies. Quantitatively, the total energy of electrons above 300 keV in sunquake-active flares is systematically different from that in sunquake-quiet flares, while the difference is marginal for electrons above 50 keV. All these facts support highly energetic electrons as a preferred driver of the sunquakes. Such an electron-driven scenario can be reasonably accommodated in the framework of a recently proposed selection rule for sunquake generation. For the remaining one event, the sunquake epicenter is cospatial with a magnetic imprint, i.e., a permanent change of magnetic field on the photosphere. Quantitative calculation shows that the flare-induced downward Lorentz force can do enough work to power the sunquake, acting as a viable sunquake driver for this specific event.

We performed a study of high redshift ($z>2$) quasars, looking for the main differences between Radio Loud Quasars (RLQ) and Radio Quiet Quasars (RQQ) in the X-ray band. Our sample of 472 RQQ and 81 RLQ was selected by cross-matching the SDSS DR7 quasars catalog with the Chandra Source Catalog. We computed the X-ray luminosity for the two samples and confirmed the X-ray luminosity excess of RLQ over RQQ. We fit the X-ray spectra assuming the absorbed power law model and obtained the photon index ($\Gamma$) values for all the sources in the sample. We excluded quasars with a low number of counts ($<10$) and large uncertainty on the best-fit photon index ($\Gamma_{err}>1$), and obtained the mean values of $\Gamma_{RLQ}=1.70 \hspace{0.5mm}_{-0.33}^{+0.36}$ and $\Gamma_{RQQ}=2.19 \hspace{0.5mm}_{-0.44}^{+0.46}$ for the RLQ and RQQ samples, respectively, showing that the RLQ have flatter (harder) X-ray spectra than RQQ. The Kuiper-two test confirms this result with the significant difference between the RLQ and RQQ photon index distributions ($D_{k}=0.37$ and P-value $= 10^{-6}$). We also evaluated the hardness ratio distributions and confirmed that the spectra of RLQ are flatter than the spectra of the RQQ. The RLQ's hard-to-soft ratio distribution is skewed towards the hard X-ray band, while the RQQ is towards the soft X-ray band. The hard-to-medium and medium-to-soft ratios show no difference.

In this work, we consider an interacting dark-fluid cosmological model in which energy exchange between dark matter and dark energy occurs through diffusion. After solving the background expansion history for a late-time universe, we attempt to constrain the cosmological parameters by comparing simulated values of the model against Supernovae Type 1A data. We consider four different cases and compare them against the LCDM model as the "true model". Our results show that the diffusive model in which dark energy flows to dark matter is the most likely alternative to LCDM model. This model is not only in line with Planck 2018 observational results but can also give a potential explanation to the so-called Hubble tension.

We combine JWST and HST imaging with ALMA~CO(2-1) spectroscopy to study the highly turbulent multi-phase intergalactic medium (IGM) in Stephan's Quintet on 25-150 pc scales. Previous Spitzer observations revealed luminous H$_2$ line cooling across a 45 kpc-long filament, created by a giant shock-wave, following the collision with an intruder galaxy NGC~7318b. We demonstrate that the MIRI/F1000W/F770W filters are dominated by 0-0~S(3)~H$_2$ and a combination of PAH and 0-0~S(5)~H$_2$ emission. They reveal the dissipation of kinetic energy as massive clouds experience collisions, interactions and likely destruction/re-cycling within different phases of the IGM. In one kpc-scaled structure, warm H$_2$ formed a triangular-shaped head and tail of compressed and stripped gas behind a narrow shell of cold H$_2$. In another region, two cold molecular clumps with very different velocities are connected by an arrow-shaped stream of warm, probably shocked, H$_2$ suggesting a cloud-cloud collision is occurring. In both regions, a high warm-to-cold molecular gas fraction indicates that the cold clouds are being disrupted and converted into warm gas. We also map gas associated with an apparently forming dwarf galaxy. We suggest that the primary mechanism for exciting strong mid-IR H$_2$ lines throughout Stephan's Quintet is through a fog of warm gas created by the shattering of denser cold molecular clouds and mixing/recycling in the post-shocked gas. Without spectroscopy, JWST cannot provide a complete picture of the kinematics and excitation of the shocked warm gas, but it reveals the rich variety of ways that different gas phases interact with one another in Stephan's Quintet.

A planet's history dictates its current potential to host habitable conditions and life. The concept of the Continuously Habitable Zone (CHZ) has been used to define the region around a star most likely to host planets with long-term habitability. However, definitions of the CHZ vary in the literature and often conflict with each other. Calculating the fraction of habitable zone planets in the CHZ as a function of stellar properties, we find that the quality of a star as a host for planets with long-term habitability and biosignatures depends strongly on the formulation of the CHZ used. For instance, older M stars are either excellent or sub-optimal hosts for CHZ planets, depending on whether one's definition of habitability prioritizes the total time spent in the habitable zone or the continuity of habitable conditions from the delivery of volatiles to its current age. In this study, we focus on Belatedly Habitable Zone (BHZ) planets, i.e. planets which enter the habitable zone after formation due to the evolution of their host star. We find that between ~29-74% of planets in the habitable zone belong to this class of BHZ planets depending on the timescale for the delivery of volatiles. Whether these planets can retain their volatiles and support habitable conditions is unclear. Since BHZ planets comprise a large portion of the planets we expect to survey for biosignatures with future missions, the open question of their habitability is an important factor for mission design, survey strategies, and the interpretation of results.

In this series of papers we present an emulator-based halo model for the non-linear clustering of galaxies in modified gravity cosmologies. In the first paper, we present emulators for the following halo properties: the halo mass function, concentration-mass relation and halo-matter cross-correlation function. The emulators are trained on data extracted from the \textsc{FORGE} and \textsc{BRIDGE} suites of $N$-body simulations, respectively for two modified gravity (MG) theories: $f(R)$ gravity and the DGP model, varying three standard cosmological parameters $\Omega_{\mathrm{m0}}, H_0, \sigma_8$, and one MG parameter, either $\bar{f}_{R0}$ or $r_{\mathrm{c}}$. Our halo property emulators achieve an accuracy of $\lesssim 1\%$ on independent test data sets. We demonstrate that the emulators can be combined with a galaxy-halo connection prescription to accurately predict the galaxy-galaxy and galaxy-matter correlation functions using the halo model framework.

Weak gravitational lensing is one of the most important probes of the nature of dark matter and dark energy. In order to extract cosmological information from next-generation weak lensing surveys (e.g., Euclid, Roman, LSST, and CSST) as much as possible, accurate measurements of weak lensing shear are required. In this work, we present a fully deep-learning-based approach to measuring weak lensing shear accurately. Our approach comprises two modules. The first one contains a CNN with two branches for taking galaxy images and PSF simultaneously, and the output of this module includes the galaxy's magnitude, size, and shape. The second module includes a multiple-layer Neural Network to calibrate weak lensing shear measurements. We name the program Forklens and make it publicly available online. Applying Forklens to CSST-like mock images, we achieve consistent accuracy with traditional approaches (such as moment-based measurement and forward model fitting) on the sources with high signal-to-noise ratios (S/N). For the sources with meagre S/N, Forklens exhibits powerful latent denoising ability and offers accurate predictions on galaxy shapes. The final shear measurements with Forklens deliver a multiplicative bias $m=-0.4\pm3.0\times10^{-3}$ and an additive bias $c=-0.5\pm1.9\times10^{-4}$. Our tests with CSST-like simulation show that Forklens is competitive with other shear measurement algorithms such as Metacalibration, while Forklens can potentially lower the S/N limit. Moreover, the whole procedure of Forklens is automated and costs about 0.6 milliseconds per galaxy, which is appropriate to adequately take advantage of the sky coverage and depth of the upcoming weak lensing surveys.

Context. While it is generally assumed that Class II sources evolve largely in isolation from their environment, many still lie close to molecular clouds and may continue to interact with them. This may result in late accretion of material onto the disk that can significantly influence disk processes and planet formation. Aims. In order to systematically study late infall of gas onto disks, we identify candidate Class II sources in close vicinity to a reflection nebula (RN) that may be undergoing this process. Methods. First we targeted Class II sources with known kilo-au scale gas structures - possibly due to late infall of material - and we searched for RNe in their vicinity in optical and near-infrared images. Second, we compiled a catalogue of Class II sources associated with RNe and looked for the large-scale CO structures in archival ALMA data. Using the catalogues of protostars and RNe, we also estimated the probability of Class II sources interacting with surrounding material. Results. All of the sources with large-scale gas structures also exhibit some reflection nebulosity in their vicinity. Similarly, at least five Class II objects associated with a prominent RNe, and for which adequate ALMA observations are available, were found to have spirals or stream-like structures which may be due to late infall. We report the first detection of these structures around S CrA. Conclusions. Our results suggest that a non-negligible fraction of Class II disks in nearby star-forming regions may be associated with RNe and could therefore be undergoing late accretion of gas. Surveys of RNe and kilo-au scale gas structures around Class II sources will allow us to better understand the frequency and impact of late-infall phenomena.

As an exact result required by the Etherington reciprocity theorem, the cosmic distance duality relation (CDDR), $\eta(z)=D_L(z)(1+z)^{-2}/D_A(z)=1$ plays an essential part in modern cosmology. In this paper, we present a new method ($\eta(z_i)/\eta(z_j)$) to use the measurements of ultra-compact structure in radio quasars (QSO) and the latest observations of type Ia supernova (SN Ia) to test CDDR. By taking the observations directly from SN Ia and QSOs, one can completely eliminate the uncertainty caused by the calibration of the absolute magnitudes of standard candles ($M_B$) and the linear sizes of standard rulers ($l_m$). Benefit from the absence of nuisance parameters involved in other currently available methods, our analysis demonstrates no evidence for the deviation and redshift evolution of CDDR up to $z=2.3$. The combination of our methodology and the machine learning Artificial Neural Network (ANN) would produce $10^{-3}$ level constraints on the violation parameter at high redshifts. Our results indicate perfect agreement between observations and predictions, supporting the persisting claims that the Etherington reciprocity theorem could still be the best description of our universe.

Stellar feedback, the energetic interaction between young stars and their birthplace, plays an important role in the star formation history of the universe and the evolution of the interstellar medium (ISM). Correctly interpreting the observations of star-forming regions is essential to understand stellar feedback, but it is a non-trivial task due to the complexity of the feedback processes and degeneracy in observations. In our recent paper, we introduced a conditional invertible neural network (cINN) that predicts seven physical properties of star-forming regions from the luminosity of 12 optical emission lines as a novel method to analyze degenerate observations. We demonstrated that our network, trained on synthetic star-forming region models produced by the WARPFIELD-Emission predictor (WARPFIELD-EMP), could predict physical properties accurately and precisely. In this paper, we present a new updated version of the cINN that takes into account the observational uncertainties during network training. Our new network named Noise-Net reflects the influence of the uncertainty on the parameter prediction by using both emission-line luminosity and corresponding uncertainties as the necessary input information of the network. We examine the performance of the Noise-Net as a function of the uncertainty and compare it with the previous version of the cINN, which does not learn uncertainties during the training. We confirm that the Noise-Net outperforms the previous network for the typical observational uncertainty range and maintains high accuracy even when subject to large uncertainties.

The cosmological principle states that the Universe is statistically homogeneous and isotropic at large distance scales. There currently exist many observations which indicate a departure from this principle. It has been shown that many of these observations can be explained by invoking superhorizon cosmological perturbations and may be consistent with the Big Bang paradigm. Remarkably, these modes simultaneously explain the observed Hubble tension, i.e., the discrepancy between the direct and indirect measurements of the Hubble parameter. We propose several tests of the cosmological principle using SKA. In particular, we can reliably extract the signal of dipole anisotropy in the distribution of radio galaxies. The superhorizon perturbations also predict a significant redshift dependence of the dipole signal which can be nicely tested by the study of signals of reionization and the dark ages using SKA. We also propose to study the alignment of radio galaxy axes as well as their integrated polarization vectors over distance scales ranging from a few Mpc to Gpc. We discuss data analysis techniques that can reliably extract these signals from data.

In this work, we investigate the existence of neutron stars (NS) in the framework of $f(\mathbb{T},\CMcal{T})$ gravity, where $\mathbb{T}$ is the torsion tensor and $\CMcal{T}$ is the trace of the energy-momentum tensor. The hydrostatic equilibrium equations are obtained, however, with $p$ and $\rho$ quantities passed on by effective quantities $\Bar{p}$ and $\Bar{\rho}$, whose mass-radius diagrams are obtained using modern equations of state (EoS) of nuclear matter derived from relativistic mean field models and compared with the ones computed by the Tolman-Oppenheimer-Volkoff (TOV) equations. Substantial changes in the mass-radius profiles of NS are obtained even for small changes in the free parameter of this modified theory. The results indicate that the use of $f(\mathbb{T},\CMcal{T})$ gravity in the study of NS provides good results for the masses and radii of some important astrophysical objects, as for example, the low-mass X-ray binary (LMXB) NGC 6397 and the pulsar of millisecond PSR J0740+6620. In addition, radii results inferred from the Lead Radius EXperiment (PREX-2) can also be described for certain parameter values.

Expected to be of the highest survey power telescope in the northern hemisphere, the Wide Field Survey Telescope (WFST) will begin its routine observations of the northern sky since 2023. WFST will produce a lot of scientific data to support the researches of time-domain astronomy, asteroids and the solar system, galaxy formation and cosmology and so on. We estimated that the 5 $\sigma$ limiting magnitudes of WFST with 30 second exposure are $u=22.31$ mag, $g=23.42$ mag, $r=22.95$ mag, $i=22.43$ mag, $z=21.50$ mag, $w=23.61$ mag. The above values are calculated for the conditions of $airmass=1.2$, seeing = 0.75 arcsec, precipitable water vapour (PWV) = 2.5 mm and Moon-object separation = $45^{\circ}$ at the darkest New Moon night of the Lenghu site (V=22.30 mag, Moon phase $\theta=0^{\circ}$). The limiting magnitudes in different Moon phase conditions are also calculated. The calculations are based on the empirical transmittance data of WFST optics, the vendor provided CCD quantum efficiency, the atmospherical model transmittance and spectrum of the site. In the absence of measurement data such as sky transmittance and spectrum, we use model data.

We here report the detection of the nebular HeII4686 line in 32 HII regions in the metal-poor collisional ring galaxy Cartwheel using the Multi-Unit Spectroscopic Explorer (MUSE) dataset. The measured I(HeII4686)/I(Hbeta) ratio varies from 0.004 to 0.07, with a mean value of 0.010+/-0.003. Ten of these 32 HII regions are coincident with the location of an Ultra Luminous X-ray (ULX) source. We used the flux ratios of important diagnostic lines and results of photoionization by Simple Stellar Populations (SSPs) to investigate the likely physical mechanisms responsible for the ionization of He+. We find that the majority of the regions (27) are consistent with photoionization by star clusters in their Wolf-Rayet (WR) phase with initial ionization parameter -3.5<logU<-2.0. Blue Bump (BB), the characteristic feature of the WR stars, however, is not detected in any of the spectra. We demonstrate that this non-detection is due to the relatively low equivalent width (EW) of the BB in metal-poor SSPs, in spite of containing sufficient number of WR stars to reproduce the observed I(HeII4686)/I(Hbeta) ratio of 1.5% at the Cartwheel metallicity of Z=0.004. The HII regions in the WR phase that are coincident with a ULX source do not show line ratios characteristic of ionization by X-ray sources. However, the ULX sources may have a role to play in the ionization of He+ in two (#99, 144) of the five regions that are not in the WR phase. Ionization by radiative shocks along with the presence of channels for the selective leakage of ionizing photons are the likely scenarios in #17 and #148, the two regions with the highest observed I(HeII4686)/I(Hbeta) ratio.

Cluster galaxies are subject to the ram pressure exerted by the intracluster medium, which can perturb or even strip away their gas while leaving the stars unperturbed. We model the distribution and kinematics of the stars and the molecular gas in four late-type cluster galaxies (JO201, JO204, JO206, and JW100), which show tails of atomic and ionized gas indicative of ongoing ram pressure stripping. We analyze MUSE@VLT data and CO data from ALMA searching for signatures of radial gas flows, ram pressure stripping, and other perturbations. We find that all galaxies, with the possible exception of JW100, host stellar bars. Signatures of ram pressure are found in JO201 and JO206, which also shows clear indications of ongoing stripping in the molecular disk outskirts. The stripping affects the whole molecular gas disk of JW100. The molecular gas kinematics in JO204 is instead dominated by rotation rather than ram pressure. We also find indications of enhanced turbulence of the molecular gas compared to field galaxies. Large-scale radial flows of molecular gas are present in JO204 and JW100, but more uncertain in JO201 and JO206. We show that our galaxy sample follows the molecular gas mass-size relation, confirming that it is essentially independent of environment even for the most extreme cases of stripping. Our findings are consistent with the molecular gas being affected by ram pressure on different timescales and less severely than the atomic and ionized gas phases, likely because the molecular gas is denser and more gravitationally bound to the galaxy.

The existence of multiple active galactic nuclei (AGN) at small projected distances on the sky is due to either the presence of multiple, in-spiraling SMBHs, or to gravitational lensing of a single AGN. Both phenomena allow us to address important astrophysical and cosmological questions. However, few kpc-separation multiple AGN are currently known. Recently, the newly-developed Gaia Multi peak (GMP) method provided numerous new candidate members of these populations. We present spatially resolved, integral-field spectroscopy of a sample of four GMP-selected multiple AGNs candidates. In all of these systems, we detect two or more components with sub-arcsec separations. We find that two of the systems are dual AGNs, one is either an intrinsic triple or a lensed dual AGN, while the last system is a chance AGN/star alignment. Our observations double the number of confirmed multiple AGNs at projected separations below 7 kpc at z > 0.5, present the first detection of a possible triple AGN in a single galaxy at z > 0.5, and successfully test the GMP method as a novel technique to discover previously unknown multiple AGNs.

Context. Transverse oscillations are ubiquitously observed in the solar corona, both in coronal loops and open magnetic flux tubes. Numerical simulations suggest that their dissipation could heat coronal loops, counterbalancing radiative losses. These models rely on a continuous driver at the footpoint of the loops. However, analytical works predict that transverse waves are subject to a cut-off in the transition region. It is thus unclear whether they can reach the corona, and indeed heat coronal loops. Aims. Our aims are to determine how the cut-off of kink waves affects their propagation into the corona, and to characterize the variation of the cut-off frequency with altitude. Methods. Using 3D magnetohydrodynamic simulations, we modelled the propagation of kink waves in a magnetic flux tube, embedded in a realistic atmosphere with thermal conduction, that starts in the chromosphere and extends into the corona. We drove kink waves at four different frequencies, and determined whether they experienced a cut-off. We then calculated the altitude at which the waves were cut-off, and compared it to the prediction of several analytical models. Results. We show that kink waves indeed experience a cut-off in the transition region, and we identified the analytical model that gives the best predictions. In addition, we show that waves with periods shorter than approximately 500 s can still reach the corona by tunnelling through the transition region, with little to no attenuation of their amplitude. This means that such waves can still propagate from the footpoints of loop, and result in heating in the corona.

We report the detection of stimulated hydrogen radio recombination line (RRL) emission from ionized gas in a $z=0.89$ galaxy using 580--1670 MHz observations from the MeerKAT Absorption Line Survey (MALS). The RRL emission originates in a galaxy that intercepts and strongly lenses the radio blazar PKS 1830-211 ($z=2.5$). This is the second detection of RRLs outside of the local universe and the first clearly associated with hydrogen. We detect effective H144$\alpha$ (and H163$\alpha$) transitions at observed frequencies of 1156 (798) MHz by stacking 17 (27) RRLs with 21$\sigma$ (14$\sigma$) significance. The RRL emission contains two main velocity components and is coincident in velocity with HI 21 cm and OH 18 cm absorption. We use the RRL spectral line energy distribution and a Bayesian analysis to constrain the density ($n_e$) and the volume-averaged pathlength ($\ell$) of the ionized gas. We determine $\log( n_e ) = 2.0_{-0.7}^{+1.0}$ cm$^{-3}$ and $\log( \ell ) = -0.7_{-1.1}^{+1.1}$ pc towards the north east (NE) lensed image, likely tracing the diffuse thermal phase of the ionized ISM in a thin disk. Towards the south west (SW) lensed image, we determine $\log( n_e ) = 3.2_{-1.0}^{+0.4}$ cm$^{-3}$ and $\log( \ell ) = -2.7_{-0.2}^{+1.8}$ pc, tracing gas that is more reminiscent of H II regions. We estimate a star formation (surface density) rate of $\Sigma_{\mathrm{SFR}} \sim 0.6$ M$_{\odot}$ yr$^{-1}$ kpc$^{-2}$ or SFR $\sim 50$ M$_{\odot}$ yr$^{-1}$, consistent with a star-forming main sequence galaxy of $M_{\star} \sim 10^{11}$ M$_{\odot}$. The discovery presented here opens up the possibility of studying ionized gas at high redshifts using RRL observations from current and future (e.g., SKA and ngVLA) radio facilities.

We present the first exoplanet phase curve measurement made with the JWST NIRSpec instrument, highlighting the exceptional stability of this newly-commissioned observatory for exoplanet climate studies. The target, WASP-121b, is an ultrahot Jupiter with an orbital period of 30.6 hr. We analyze two broadband light curves generated for the NRS1 and NRS2 detectors, covering wavelength ranges of 2.70-3.72 micron and 3.82-5.15 micron, respectively. Both light curves exhibit minimal systematics, with approximately linear drifts in the baseline flux level of 30 ppm/hr (NRS1) and 10 ppm/hr (NRS2). Assuming a simple brightness map for the planet described by a low-order spherical harmonic dipole, our light curve fits suggest that the phase curve peaks coincide with orbital phases $3.36 \pm 0.11$ deg (NRS1) and $2.66 \pm 0.12$ deg (NRS2) prior to mid-eclipse. This is consistent with the strongest dayside emission emanating from eastward of the substellar point. We measure planet-to-star emission ratios of $3,924 \pm 7$ ppm (NRS1) and $4,924 \pm 9$ ppm (NRS2) for the dayside hemisphere, and $136 \pm 8$ ppm (NRS1) and $630 \pm 10$ ppm (NRS2) for the nightside hemisphere. The latter nightside emission ratios translate to planetary brightness temperatures of $926 \pm 12$ K (NRS1) and $1,122 \pm 10$ K (NRS2), which are low enough for a wide range of refractory condensates to form, including enstatite and forsterite. A nightside cloud deck may be blocking emission from deeper, hotter layers of the atmosphere, potentially helping to explain why cloud-free 3D general circulation model simulations systematically over-predict the nightside emission for WASP-121b.

The short timescale of the solar flare reconnection process has long proved to be a puzzle. Recent studies suggest the importance of the formation of plasmoids in the reconnecting current sheet, with quantifying the aspect ratio of the width to length of the current sheet in terms of a negative power $\alpha$ of the Lundquist number, i.e. $S^{-\alpha}$, being key to understanding the onset of plasmoids formation. In this paper we make the first application of theoretical scalings for this aspect ratio to observed flares to evaluate how plasmoid formation may connect with observations. We find that for three different flares showing plasmoids a range of $\alpha$ values of $\alpha= 0.27$ to $0.31$. The values in this small range implies that plasmoids may be forming before the theoretically predicted critical aspect ratio ($\alpha=1/3$) has been reached, potentially presenting a challenge for the theoretical models.

We present an analysis of the star-formation rates (SFRs) and dust attenuation properties of star-forming galaxies at $2.7\leq z<6.5$ drawn from the Cosmic Evolution Early Release Science (CEERS) Survey. Our analysis is based on {\it JWST}/NIRSpec Micro-Shutter Assembly (MSA) $R\sim1000$ spectroscopic observations covering approximately $1-5$$\mu$m. Our primary rest-frame optical spectroscopic measurements are H$\alpha$/H$\beta$ Balmer decrements, which we use as an indicator of nebular dust attenuation. In turn, we use Balmer decrements to obtain dust-corrected H$\alpha$-based SFRs (i.e., SFR(H$\alpha$)). We construct the relationship between SFR(H$\alpha$) and stellar mass ($M_*$) in three bins of redshift ($2.7\leq z< 4.0$, $4.0\leq z< 5.0$, and $5.0\leq z<6.5$), which represents the first time the star-forming main sequence has been traced at these redshifts using direct spectroscopic measurements of Balmer emission as a proxy for SFR. In tracing the relationship between SFR(H$\alpha$) and $M_*$ back to such early times ($z>3$), it is essential to use a conversion factor between H$\alpha$ and SFR that accounts for the subsolar metallicity prevalent among distant galaxies. We also use measured Balmer decrements to investigate the relationship between dust attenuation and stellar mass out to $z\sim6$. The lack of significant redshift evolution in attenuation at fixed stellar mass, previously confirmed using Balmer decrements out to $z\sim2.3$, appears to hold out to $z\sim 6.5$. Given the rapidly evolving gas, dust, and metal content of star-forming galaxies at fixed mass, this lack of significant evolution in attenuation provides an ongoing challenge to explain.

Wavefront sensing and control (WFSC) will play a key role in improving the stability of future large segmented space telescopes while relaxing the thermo-mechanical constraints on the observatory structure. Coupled with a coronagraph to reject the light of an observed bright star, WFSC enables the generation and stabilisation of a dark hole (DH) in the star image to perform planet observations. While WFSC traditionally relies on a single wavefront sensor (WFS) input to measure wavefront errors, the next generation of instruments will require several WFSs to address aberrations with different sets of spatial and temporal frequency contents. The multiple measurements produced in such a way will then have to be combined and converted to commands for deformable mirrors (DMs) to modify the wavefront subsequently. We asynchronously operate a loop controlling the high-order modes digging a DH and a control loop that uses the rejected light by a Lyot coronagraph with a Zernike wavefront sensor to stabilize the low-order aberrations. Using the HiCAT testbed with a segmented telescope aperture, we implement concurrent operations and quantify the expected cross-talk between the two controllers. We then present experiments that alternate high-order and low-order control loops to identify and estimate their respective contributions. We show an efficient combination of the high-order and low-order control loops, keeping a DH contrast better than 5 x 10-8 over a 30 min experiment and stability improvement by a factor of 1.5. In particular, we show a contrast gain of 1.5 at separations close to the DH inner working angle, thanks to the low-order controller contribution. Concurrently digging a DH and using the light rejected by a Lyot coronagraph to stabilize the wavefront is a promising path towards exoplanet imaging and spectroscopy with future large space observatories.

As galactic halos are not directly visible, there are many ambiguities regarding their composition and rotational velocity. Though most of the dark matter is non-baryonic, {\it some fraction is}, and it can be used to trace the halo rotation. Asymmetries in the CMB towards M31 had been seen in the Planck data and ascribed to the rotational Doppler shift of the M31 halo. Subsequently, the same methods were used in the direction of five other galaxies belonging to the Local Group, namely M33, M81, M82, NGC 5128, and NGC 4594. It had been proved that there could be stable clouds of gas and dust in thermal equilibrium with the CMB at 2.7 K, which had been called ``virial clouds''. In this paper, adopting this scenerio, an attempt is made to constrain the fraction of dust grains and gas molecules in the clouds.

Chromospheric inferences rely on the interpretation of spectral lines that are formed under Non-Local Thermodynamic Equilibrium (NLTE) conditions. In the presence of oscillations, changes in the opacity impact the response height of the spectral lines and hinder the determination of the real properties of the fluctuations. We aim to explore the relationship between the chromospheric oscillations inferred by NLTE inversion codes and the waves' intrinsic fluctuations in velocity and temperature. Numerical simulations of wave propagation in an umbra have been computed with the code MANCHA. The NLTE synthesis and inversion code NICOLE has been used to compute spectropolarimetric Ca II 8542 \AA\ line profiles for the models obtained from the simulations. The synthetic profiles have been inverted and the inferences from the inversions have been compared with the known simulated atmospheres. NLTE inversions of the Ca II 8542 \AA\ line capture low-frequency oscillations, including those in the main band of chromospheric oscillations around 6 mHz. In contrast, waves with frequencies above 9 mHz are poorly characterized. Velocity oscillations at those higher frequencies exhibit clear indications of opacity fluctuations. The main response of the line to velocity fluctuations comes from low chromospheric heights, whereas the response to temperature shows sudden jumps between the high photosphere and the low chromosphere. This strong variation in the heights where the line is sensitive to temperature is revealed as a strong oscillatory power in the inferred fluctuations. Our results validate the use of NLTE inversions to study chromospheric oscillations with frequencies below 9 mHz. The interpretation of higher frequency oscillations and the power of temperature oscillations must be addressed with care since they exhibit signatures of opacity oscillations.

The brighter-fatter effect affects all CCD sensors to various degrees. Deep-depleted thick sensors are seriously affected and the measurement of galaxy shapes for cosmic shear measurements requires an accurate correction of the effect in science images. We describe the whole correction chain we have implemented for the CCDs of the Hyper Suprime-Cam imager on the Subaru Telescope. We derive non linearity corrections from a new sequence of flat field images, and measure their statistics, namely their two-pixel function. We constrain an electrostatic model from flat field statistics that we use to correct science images. We find evidence that some fraction of the observed variance and some covariances is not due to the combination of Poisson statistics and electrostatics -- and the cause remains elusive. We then have to ignore some measurements when deriving the electrostatic model. Over a wide range of image qualities and in the 5 bands of the imager, stars in corrected science images exhibit size variations with flux small enough to predict the point spread function for faint objects to an accuracy better than $10^{-3}$ for the trace of second moments -- and even better for the ellipticity and the fourth radial moment. This performance is sufficient for upcoming large-scale cosmic shear surveys such as Rubin/LSST.

We introduce a new clustering algorithm, MulGuisin (MGS), that can find galaxy clusters using topological information from the galaxy distribution. This algorithm was first introduced in an LHC experiment as a Jet Finder software, which looks for particles that clump together in close proximity. The algorithm preferentially considers particles with high energies and merges them only when they are closer than a certain distance to create a jet. MGS shares some similarities with the minimum spanning tree (MST) since it provides both clustering and graph-based topology information. Also, similar to the density-based spatial clustering of applications with noise (DBSCAN), MGS uses the ranking or the local density of each particle to construct clustering. In this paper, we compare the performances of clustering algorithms using some controlled data and some realistic simulation data as well as the SDSS observation data, and we demonstrate that our new algorithm find clusters most efficiently and it defines galaxy clusters in a way that most closely resembles human vision.

Saturn's rings are composed of icy grains, most in the mm to m size ranges, undergoing several collisions per orbit. Their collective behaviour generates a remarkable array of structure over many orders of magnitude, much of it not well understood. On the other hand, the collisional properties and parameters of individual ring particles are poorly constrained; usually N-body simulations and kinetic theory employ hard-sphere models with a coefficient of restitution $\epsilon$ that is constant or a decreasing function of impact speed. Due to plastic deformation of surface regolith, however, it is likely that $\epsilon$ will be more complicated, at the very least a non-monotonic function. We undertake N-body simulations with the REBOUND code with non-monotonic $\epsilon$ laws to approximate surfaces that are friable but not sticking. Our simulations reveal that such ring models can support two thermally stable steady states for the same (dynamical) optical depth: a cold and a warm state. If the ring breaks up into radial bands of one or the other state, we find that warmer states tend to migrate into the colder states via a coherent travelling front. We also find stationary `viscous' fronts, which connect states of different optical depth, but the same angular momentum flux. We discuss these preliminary results and speculate on their implications for structure formation in Saturn's B and C-rings, especially with respect to structures that appear in Cassini images but not in occultations.

Observations of the first billion years of cosmic history are currently limited. We demonstrate the synergy between observations of the sky-averaged 21-cm signal from neutral hydrogen and interferometric measurements of the corresponding spatial fluctuations. By jointly analysing data from SARAS3 (redshift $z\approx15-25$) and limits from HERA ($z\approx8$ and $10$), we produce the tightest constraints to date on the astrophysics of galaxies 200 million years after the Big Bang. We disfavour at $95\%$ confidence scenarios in which power spectra are $\geq126$ mK$^{2}$ at $z=25$ and the sky-averaged signals are $\leq-277$ mK.

In this work, we used N-body simulations and a radiative transfer package to model the evolution of eccentric debris discs produced by giant impacts between planetary embryos. This included how the morphology and infrared emission of these discs varied with embryo eccentricity and collision true anomaly. We found that eccentric discs inherit the eccentric properties of the centre of mass orbit of the two colliding embryos. However, the orientation of the collision with the respect to this orbit plays a key role in determining how closely the disc material resembles the centre of mass orbit. Additionally, we found that increased eccentricity acted to suppress the formation of certain short-term variations in the disc emission depending on the collision position. These short-term variations have been associated with an observational phenomenon called extreme debris discs. Short-term variability has been suggested as a potential signature for giant impacts.

Aims. GAIA delivers the positions and velocities of stars at unprecedented precision. Therefore, for star clusters, there exists much higher confidence in whether a specific star is a member of a particular group. However, membership determination is still challenging for young star clusters. At ages 2-10 Myr, the gas is expelled, leading to cluster expansion, while many former members become unbound. We aim to assess the accuracy of the methods used to distinguish between bound and unbound cluster members. After identifying the most suitable technique, we wish to understand which of the two populations provides more insights into the initial configuration and the dynamic history of a cluster. Methods. Here, we perform N-body simulations of the dynamics of such young star clusters. We investigate how cluster dynamics and observational limitations affect the recovered information about the cluster from a theoretical perspective. Results. We find that the much-used method of distance and velocity cutoffs for membership determination often leads to false negatives and positives alike. Often observational studies focus on the stars remaining bound. However, they quickly lose the memory of the pre-gas expulsion phase due to interactions with other cluster members. Our study shows that the unbound stars hold the key to charting a cluster's dynamic history. Backtracking unbound stars can provide the original cluster size and determine the time of gas expulsion. This information is lost in the bound population. In addition, former members are often better indicators for disc lifetimes or initial binary fractions. We apply the backtracking analysis, with varying success, to the clusters: Upper Scorpius and NGC 6530. For highly substructured clusters such as Upper Scorpius, backtracking to the individual subcluster centres will provide better results in the future (abridged).

Recent work has shown that searches for diffuse radio emission by MeerKAT - and eventually the SKA - are well suited to provide some of the strongest constraints yet on dark matter annihilations. To make full use of the observations by these facilities, accurate simulations of the expected dark matter abundance and diffusion mechanisms in these astrophysical objects are required. However, because of the computational costs involved, various mathematical and numerical techniques have been developed to perform the calculations in a feasible manner. Here we provide the first quantitative comparison between methods that are commonly used in the literature, and outline the applicability of each one in various simulation scenarios. These considerations are becoming ever more important as the hunt for dark matter continues into a new era of precision radio observations.

We present our investigations of the physical and dynamical properties of selected Earth co-orbital asteroids. The photometric optical light curves as well as rotation periods and pole solutions for a sample of four Earth co-orbital asteroids, namely (138175) 2000 EE104 (P=13.9476+/-0.0051 hrs), (418849) 2008 WM64 (P=2.4077+/-0.0001 hrs), 2016 CA138 (P=5.3137+/-0.0016 hrs) and 2017 SL16 (P=0.3188+/-0.0053 hrs), are determined or improved and presented in this work. For this investigation, we combine observations carried out at the Bulgarian National Astronomical Observatory - Rozhen using the FoReRo2 instrument attached to the 2mRCC telescope as well as sparse data from AstDys2 database. Parallel to the rotational properties we did numerical dynamical simulations to investigate the orbital stability of those objects and to find out if there is a relation with their rotational properties. Our results show that the orbit stability is affected by the orbit itself and mainly its eccentricity and inclination, which are responsible for the close encounters with other Solar system planets. We cannot make a definitive conclusion about the relation between orbit stability and the rotational state of the asteroids, so we need further investigations and observations in order to prove or disprove it.

With over 5,000 exoplanets currently detected, there is a need for a primary classification method to prioritise candidates for biosignature observations. Here, we develop a classification method to categorise rocky exoplanets based on their closest solar system analogue using available data of observed stellar and planetary features, masses, and radii, to model non-thermal atmospheric escape, thermal atmospheric escape, and stellar irradiation boundaries. Applying this classification method to the 720 rocky exoplanets in our sample with uncertainties in planetary masses, radii, stellar temperatures, and fluxes propagated via a Monte Carlo model indicates that 22% $\pm$ 8% are Mercury analogues, 39% $\pm$ 4% are Mars analogues, 11% $\pm$ 1% are Venus analogues, 2% $\pm$ 1% are Earth analogues, and 26% $\pm$ 12% are without a known planetary counterpart in our solar system. Extrapolating to conditions on LHS 3844b and GJ 1252b, our classification method gives results reasonably consistent with current observations. Subsequently, to demonstrate the functionality of this classification method, we plot our catalogued sample of exoplanets on an adjusted surface pressure versus temperature phase diagram, presenting more realistic estimates of the potential surface phases (gas, liquid or ice). Our new classification method could help target selection for future exoplanet characterisation missions.

FU Orionis-type objects (FUors) are low-mass pre-main-sequence objects which go through a short-lived phase (~100 years) of increased mass accretion rate (from 10^-8 to 10^-4 M_sun yr^-1). These eruptive young stars are in the early stages of stellar evolution and, thus, still deeply embedded in a massive envelope that feeds material to the circumstellar disk that is then accreted onto the star. Some FUors drive molecular outflows, i.e. low-velocity wide-angle magneto-hydrodynamical winds, that inject energy and momentum back to the surrounding envelopes, and help clear the material surrounding the young star. Here we present a 12CO (3--2), 13CO (3--2) and 12CO (4--3) survey of 20 FUor-type eruptive young stars observed with APEX. We use our 13CO (3--2) observations to measure the masses of the envelopes surrounding each FUor and find an agreement with the FUor evolutionary trend found from the 10um silicate feature. We find outflows in 11 FUors, calculate their masses and other kinematic properties, and compare these with those of outflows found around quiescent young stellar objects gathered from the literature. This comparison indicates that outflows in FUors are more massive than outflows in quiescent sources, and that FUor outflows have a higher ratio outflow mass with respect to the envelope than the quiescent sample, indicating that the eruptive young stars have lower star-forming efficiencies. Finally, we found that the outflow forces in FUors are similar to those of quiescent young stellar objects, indicating that their accretion histories are similar or that the FUor outflows have lower velocities.

Type IIn supernovae potentially constitute a large fraction of the gravitationally lensed supernovae predicted to be found with upcoming facilities. However, the local rate is used for these estimates, which is assumed to be independent of properties such as the host galaxy mass. Some studies hint that a host galaxy mass bias may exist for IIn supernovae. This paper aims to provide an updated local IIn supernova-to-core-collapse ratio based on data from the Palomar Transient Factory (PTF) and the Zwicky Transient Facility (ZTF) Bright Transient Survey (BTS). Furthermore, the goal is to investigate the dependency of the IIn supernova peak magnitude on the host galaxy mass and the consequences of a possible host galaxy mass preference on the volumetric rate of type IIn supernovae. We constructed approximately volume-limited subsamples to determine the local IIn supernova-to-core-collapse ratio. We investigated the absolute peak magnitude of a subsample of type IIn and superluminous II or IIn supernovae exploring how this relates to the i-band magnitude of the host galaxies (as a proxy for stellar mass). We presented a method to quantify the effect of a potential preference for low-mass host galaxies utilizing the UniverseMachine algorithm. The IIn supernova-to-core-collapse ratios for PTF and BTS are 0.046 +- 0.013 and 0.048 +- 0.011, respectively, which results in a ratio of 0.047 +- 0.009, which is consistent with the ratio of 0.05 currently used to estimate the number of gravitationally lensed IIn supernovae. We report fainter host galaxy median absolute magnitudes for type IIn brighter than -20.5 mag with a 3 sigma significance. If the IIn supernova-to-core-collapse ratio were described by the power law model $IIn/CC = 0.15 \cdot \log(M/M_{\odot})^{-0.05}$, we would expect a slightly elevated volumetric rate for redshifts beyond 3.2.

We perform a deep survey of planetary nebulae (PNe) in the spiral galaxy NGC 300 to construct its planetary nebula luminosity function (PNLF). We aim to derive the distance using the PNLF and to probe the characteristics of the most luminous PNe. We analyse 44 fields observed with MUSE at the VLT, covering a total area of $\sim11$ kpc$^2$. We find [OIII]5007 sources using the differential emission line filter (DELF) technique. We identify PNe through spectral classification using the aid of the BPT-diagram. The PNLF distance is derived using the maximum likelihood estimation technique. For the more luminous PNe, we also measure their extinction using the Balmer decrement. We estimate the luminosity and effective temperature of the central stars of the luminous PNe, based on estimates of the excitation class and the assumption of optically thick nebulae. We identify 107 PNe and derive a most-likely distance modulus $(m-M)_0 = 26.48^{+0.11}_{-0.26}$ ($d = 1.98^{+0.10}_{-0.23}$ Mpc). We find that the PNe at the PNLF cut-off exhibit relatively low extinction, with some high extinction cases caused by local dust lanes. We present the lower limit luminosities and effective temperatures of the central stars for some of the brighter PNe. We also identify a few Type I PNe that come from a young population with progenitor masses $>2.5 \, M_\odot$, however do not populate the PNLF cut-off. The spatial resolution and spectral information of MUSE allow precise PN classification and photometry. These capabilities also enable us to resolve possible contamination by diffuse gas and dust, improving the accuracy of the PNLF distance to NGC 300.

For centuries, humanity wondered if there were other worlds like ours in the Universe. For about a quarter of a century, we have known that planetary systems exist around other stars, and more than 3800 exoplanetary systems have been discovered so far. However, the large majority of the exoplanets remain invisible to us since we usually infer their presence by their effect on their star. The chapter is devoted to stellar hosts and their characteristics, emphasizing their description by discovery method and links between the properties of the host stars and their planets. The star-planet connection is vital to constrain the theories on the formation and evolution of planetary systems, including our own.

A major goal in the search for extraterrestrial life is the detection of liquid water on the surface of exoplanets. On terrestrial planets, volcanic outgassing is a significant source of atmospheric and surface water and a major contributor to the long-term evolution of the atmosphere. The rate of volcanism depends on the interior evolution and on numerous feedback processes between atmosphere and interior, which continuously shape atmospheric composition, pressure, and temperature. We present the results of a comprehensive 1D model of the coupled evolution of the interior and atmosphere of rocky exoplanets that combines central feedback processes between these two reservoirs. We carried out more than 280,000 simulations over a wide range of mantle redox states and volatile content, planetary masses, interior structures and orbital distances in order to robustly assess the emergence, accumulation and preservation of surface water on rocky planets. To establish a conservative baseline of which types of planets can outgas and sustain water on their surface, we focus here on stagnant-lid planets. We find that only a narrow range of the mantle redox state around the iron-w\"ustite buffer allows forming atmospheres that lead to long-term habitable conditions. At oxidizing conditions similar to those of the Earth's mantle, most stagnant-lid planets transition into a runaway greenhouse regime akin to Venus due to strong CO$_2$ outgassing. At more reducing conditions, the amount of outgassed greenhouse gases is often too low to keep surface water from freezing. In addition, Mercury-like planets with large metallic cores are able to sustain habitable conditions at an extended range of orbital distances as a result of lower volcanic activity.

The multi-dimensional phase space density (both position and velocity) of star-forming regions may encode information on the initial conditions of star and planet formation. Recently, a new metric based on the Mahalanobis distance has been used to show that hot Jupiters are more likely to be found around exoplanet host-stars in high 6D phase space density, suggesting a more dynamic formation environment for these planets. However, later work showed that this initial result may be due to a bias in the age of hot Jupiters and the kinematics of their host stars. We test the ability of the Mahalanobis distance and density to differentiate more generally between star-forming regions with different morphologies by applying it to static regions that are either substructured or smooth and centrally concentrated. We find that the Mahalanobis distance is unable to distinguish between different morphologies, and that the initial conditions of the N-body simulations cannot be constrained using only the Mahalanobis distance or density. Furthermore, we find that the more dimensions in the phase space the less effective the Mahalanobis density is at distinguishing between different initial conditions. We show that a combination of the mean three-dimensional (x, y, z) Mahalanobis density and the Q-parameter for a region can constrain its initial virial state. However this is due to the discriminatory power of the Q-parameter and not from any extra information imprinted in the Mahalanobis density. We therefore recommend continued use of multiple diagnostics for determining the initial conditions of star-forming regions, rather than relying on a single multi-dimensional metric.

The optical and near-ultraviolet (NUV) continuum radiation in M dwarf flares is thought to be the impulsive response of the lower stellar atmosphere to magnetic energy release and electron acceleration at coronal altitudes. This radiation is sometimes interpreted as evidence of a thermal photospheric spectrum with $T \approx 10^4$ K. However, calculations show that standard solar flare coronal electron beams lose their energy in a thick target of gas in the upper and middle chromosphere (log$_{10}$ column mass /[g cm$^{-2}$] $\lesssim -3$). At larger beam injection fluxes, electric fields and instabilities are expected to further inhibit propagation to low altitudes. We show that recent numerical solutions of the time-dependent equations governing the power-law electrons and background coronal plasma (Langmuir and ion-acoustic) waves from Kontar et al. produce order-of-magnitude larger heating rates than occur in the deep chromosphere through standard solar flare electron beam power-law distributions. We demonstrate that the redistribution of beam energy above $E \gtrsim 100$ keV in this theory results in a local heating maximum that is similar to a radiative-hydrodynamic model with a large, low-energy cutoff and a hard power-law index. We use this semi-empirical forward modeling approach to produce opaque NUV and optical continua at gas temperatures $T \gtrsim 12,000$ K over the deep chromosphere with log$_{10}$ column mass /[g cm$^{-2}$] of $-1.2$ to $-2.3$. These models explain the color temperatures and Balmer jump strengths in high-cadence M dwarf flare observations, and they clarify the relation among atmospheric, radiation, and optical color temperatures in stellar flares.

We present the results obtained with an end-to-end simulator of an Extreme Adaptive Optics (XAO) system control loop. It is used to predict its on-sky performances and to optimise the AO loop algorithms. It was first used to validate a novel analytical model of the fitting error, a limit due to the Deformable Mirror (DM) shape. Standard analytical models assume a sharp correction under the DM cutoff frequency, disregarding the transition between the AO corrected and turbulence dominated domains. Our model account for the influence function shape in this smooth transition. Then, it is well-known that Shack-Hartmann wavefront sensors (SH-WFS) have a limited spatial bandwidth, the high frequencies of the wavefront being seen as low frequencies. We show that this aliasing error can be partially compensated (both in terms of Strehl ratio and contrast) by adding priors on the turbulence statistics in the framework of an inverse problem approach. This represents an alternative to the standard additional optical filter used in XAO systems. In parallel to this numerical work, a bench was aligned to experimentally test the AO system and these new algorithms comprising a DM192 ALPAO deformable mirror and a 15x15 SH-WFS. We present the predicted performances of the AO loop based on end-to-end simulations.

The recently-proposed Aether Scalar Tensor (AeST) model reproduces both the successes of particle dark matter on cosmological scales and those of Modified Newtonian Dynamics (MOND) on galactic scales. But the AeST model reproduces MOND only up to a certain maximum galactocentric radius. Since MOND is known to fit very well to observations at these scales, this raises the question whether the AeST model comes into tension with data. We test whether or not the AeST model is in conflict with observations using a recent analysis of data for weak gravitational lensing. We solve the equations of motion of the AeST model, analyze the solutions' behavior, and compare the results to observational data. The AeST model shows some deviations from MOND at the radii probed by weak gravitational lensing. This creates a tension with the data. To entirely rule out the model, however, a more advanced data analysis as well as an improved theoretical understanding would be necessary.

The CHIME/FRB project has detected hundreds of fast radio bursts (FRBs), providing an unparalleled population to probe statistically the foreground media that they illuminate. One such foreground medium is the ionized halo of the Milky Way (MW). We estimate the total Galactic electron column density from FRB dispersion measures (DMs) as a function of Galactic latitude using four different estimators, including ones that assume spherical symmetry of the ionized MW halo and ones that imply more latitudinal-variation in density. Our observation-based constraints of the total Galactic DM contribution for $|b|\geq 30^\circ$, depending on the Galactic latitude and selected model, span 87.8 - 141 pc cm^-3. This constraint implies upper limits on the MW halo DM contribution that range over 52-111 pc cm^-3. We discuss the viability of various gas density profiles for the MW halo that have been used to estimate the halo's contribution to DMs of extragalactic sources. Several models overestimate the DM contribution, especially when assuming higher halo gas masses (~ 3.5 x 10^12 solar masses). Some halo models predict a higher MW halo DM contribution than can be supported by our observations unless the effect of feedback is increased within them, highlighting the impact of feedback processes in galaxy formation.

We take advantage of the extraordinary weather conditions available between February and March 2022 over Spain to analyze the brightest fireballs recorded by the monitoring stations of the Spanish Meteor Network (SPMN). We study the atmospheric flight of 15 large meteoroids to determine if they are meteorite dropper events to prepare campaigns to search for freshly fallen extraterrestrial material. We investigate their origins in the Solar System and their dynamic association with parent bodies and meteoroid streams. Employing our Python pipeline 3D-FireTOC, we reconstruct the atmospheric trajectory utilizing ground-based multi-station observations and compute the heliocentric orbit. In addition, we applied an ablation model to estimate the initial and terminal mass of each event. Using a dissimilarity criterion and propagating backward in time, we check the connection of these meteoroids with known complexes and near-Earth objects. We also calculate if the orbits are compatible with recent meteoroid ejections. We find that ~27% of these fireballs are dynamically associated with minor meteoroid streams and exhibit physical properties of cometary bodies, as well as one associated with a near-Earth asteroid. We identify two meteorite-producing events; however, the on-site search was unsuccessful. By considering that these fireballs are mostly produced by cm-sized rocks that might be the fragmentation product of much larger meteoroids, our findings emphasize the idea that the population of near-Earth objects is a source of near-term impact hazards, existing large Earth-colliding meteoroids in the known complexes.

The First Ionization Potential (FIP) bias, whereby elemental abundances for low FIP elements in different coronal structures vary from their photospheric values and may also vary with time, has been widely studied. In order to study the temporal variation, and to understand the physical mechanisms giving rise to the FIP bias, we have investigated the hot cores of three ARs using disk-integrated soft X-ray spectroscopic observation with the Solar X-ray Monitor (XSM) onboard Chandrayaan-2. Observations for periods when only one AR was present on the solar disk were used so as to ensure that the AR was the principal contributor to the total X-ray intensity. The average values of temperature and EM were ~3 MK and 3.0E46/cm3 respectively. Regardless of the age and activity of the AR, the elemental abundances of the low FIP elements, Al, Mg, and Si were consistently higher than their photospheric values. The average FIP bias for Mg and Si was ~3, whereas the FIP bias for the mid-FIP element, S, was ~1.5. However, the FIP bias for the lowest FIP element, Al, was observed to be higher than 3, which, if real, suggests a dependence of the FIP bias of low FIP elements on their FIP value. Another major result from our analysis is that the FIP bias of these elements is established in within ~10 hours of emergence of the AR and then remains almost constant throughout its lifetime.

The dispersion of fast radio bursts (FRBs) is a measure of the large-scale electron distribution. It enables measurements of cosmological parameters, especially of the expansion rate and the cosmic baryon fraction. The number of events is expected to increase dramatically over the coming years, and of particular interest are bursts with identified host galaxy and therefore redshift information. In this paper, we explore the covariance matrix of the dispersion measure (DM) of FRBs induced by the large-scale structure, as bursts from a similar direction on the sky are correlated by long wavelength modes of the electron distribution. We derive analytical expressions for the covariance matrix and examine the impact on parameter estimation from the FRB dispersion measure - redshift relation. The covariance also contains additional information that is missed by analysing the events individually. For future samples containing over $\sim300$ FRBs with host identification over the full sky, the covariance needs to be taken into account for unbiased inference, and the effect increases dramatically for smaller patches of the sky.

The Southern African Large Telescope (SALT) survey of helium-rich hot subdwarfs aims to explore evolutionary pathways amongst groups of highly-evolved stars. The selection criteria mean that several hot white dwarfs and related objects have also been included. This paper reports the discovery and analysis of eight new very hot white dwarf and pre-white dwarf stars with effective temperatures exceeding 100,000 K. They include two PG1159 stars, one DO white dwarf, three O(He) and two O(H) stars. One of the O(H) stars is the central star of a newly-discovered planetary nebula, the other is the hottest `naked' O(H) star. Both of the PG1159 stars are GW Vir variables, one being the hottest GW Vir star measured and a crucial test for pulsation stability models. The DO white dwarf is also the hottest in its class.

The simultaneous observation of gravitational waves (GW) and prompt electromagnetic counterparts from the merger of two neutron stars can help reveal the properties of extreme matter and gravity during and immediately after the final plunge. Rapid sky localization of these sources is crucial to facilitate such multi-messenger observations. Since GWs from binary neutron star (BNS) mergers can spend up to 10-15 mins in the frequency bands of the detectors at design sensitivity, early warning alerts and pre-merger sky localization can be achieved for sufficiently bright sources, as demonstrated in recent studies. In this work, we present pre-merger BNS sky localization results using CBC-SkyNet, a deep learning model capable of inferring sky location posterior distributions of GW sources at orders of magnitude faster speeds than standard Markov Chain Monte Carlo methods. We test our model's performance on a catalog of simulated injections from Sachdev et al. (2020), recovered at 0-60 secs before merger, and obtain comparable sky localization areas to the rapid localization tool BAYESTAR. These results show the feasibility of our model for rapid pre-merger sky localization and the possibility of follow-up observations for precursor emissions from BNS mergers.

Early dark energy (EDE) is one of the most promising possibilities in order to resolve the Hubble tension: the discrepancy between early and late-Universe measurements of the Hubble constant. In this paper we propose a model of a scalar field which can explain both EDE and late Dark Energy (DE) in a joined manner without additional fine-tuning. The field features kinetic poles as with alpha-attractors. Our model provides an injection of EDE near matter-radiation equality, and redshifts away shortly after via free-fall, later refreezing to become late-time DE at the present day. Using reasonable estimates of the current constraints on EDE from the literature, we find that the parameter space is narrow but viable. As such our model is readily falsifiable. In contrast to other work in EDE, our model is non-oscillatory, which causes its decay to be faster than that of the usual oscillatory EDE, thereby achieving better agreement with observations.

The introduction of deep wide-field surveys in recent years and the adoption of machine learning techniques have led to the discoveries of $\mathcal{O}(10^4)$ strong gravitational lensing systems and candidates. However, the discovery of multiply lensed transients remains a rarity. Lensed transients and especially lensed supernovae are invaluable tools to cosmology as they allow us to constrain cosmological parameters via lens modeling and the measurements of their time delays. In this paper, we develop a pipeline to perform a targeted lensed transient search. We apply this pipeline to 5807 strong lenses and candidates, identified in the literature, in the DESI Legacy Imaging Surveys Data Release 9 (DR9) footprint. For each system, we analyze every exposure in all observed bands (DECam $g$, $r$, and $z$). Our pipeline finds, groups, and ranks detections that are in sufficient proximity temporally and spatially. After the first round of inspection, for promising candidate systems, we further examine the newly available DR10 data (with additional $i$ and $\textrm{Y}$ bands). Here we present our targeted lensed supernova search pipeline and seven new lensed supernova candidates, including a very likely lensed supernova $-$ probably a Type Ia $-$ in a system with an Einstein radius of $\sim 1.5''$.

Interferometers (e.g. ALMA and NOEMA) allow us to obtain the detailed brightness distribution of astronomical sources in 3 dimensions (R.A., Dec., frequency). However, the spatial correlation of the noise makes it difficult to evaluate the statistical uncertainty of the measured quantities and the statistical significance of the results obtained. The noise correlation properties in the interferometric image are fully characterized and easily measured by the noise autocorrelation function (ACF). We present the method for (1) estimating the statistical uncertainty due to the correlated noise in the spatially integrated flux and spectra directly, (2) simulating the correlated noise to perform a Monte Carlo simulation in image analyses, and (3) constructing the covariance matrix and chi-square $\chi^2$ distribution to be used when fitting a model to an image with spatially correlated noise, based on the measured noise ACF. We demonstrate example applications to scientific data showing that ignoring noise correlation can lead to significant underestimation of statistical uncertainty of the results and false detections/interpretations.

The large-scale structure is a major source of cosmological information. However, next-generation photometric galaxy surveys will only provide a distorted view of cosmic structures due to large redshift uncertainties. To address the need for accurate reconstructions of the large-scale structure in presence of photometric uncertainties, we present a framework that constrains the three-dimensional dark matter density jointly with galaxy photometric redshift probability density functions (PDFs), exploiting information from galaxy clustering. Our forward model provides Markov Chain Monte Carlo realizations of the primordial and present-day dark matter density, inferred jointly from data. Our method goes beyond 2-point statistics via field-level inference. It accounts for all observational uncertainties and the survey geometry. We showcase our method using mock catalogs that emulate next-generation surveys with a worst-case redshift uncertainty, equivalent to ${\sim}300$ Mpc. On scales $150$ Mpc, we improve the cross-correlation of the photometric galaxy positions with the ground truth from $28\%$ to $86\%$. The improvement is significant down to $13$ Mpc. On scales $150$ Mpc, we achieve a cross-correlation of $80-90\%$ with the ground truth for the dark matter density, radial peculiar velocities, tidal shear and gravitational potential.

A suggested model for quasi--periodic eruptions (QPEs) from galaxy nuclei invokes a white dwarf in an eccentric orbit about the central massive black hole. I point out that the extreme mass ratio allows the presence of strong Lindblad resonances in the accretion disc. These are important for the stability of mass transfer, and may trigger the eruptions themselves by rapidly transferring angular momentum from the accretion disc (which is likely to be eccentric itself) to the orbiting WD companion at pericentre. I consider the effects of von Zeipel--Lidov--Kozai (ZLK) cycles caused by a perturber on a more distant orbit about the central black hole. I show that ZLK cycles can change the orbital periods of QPE systems on timescales much shorter than the mass transfer time, as seen in ASASSN-14ko, and produce correlated short--term variations of their mass transfer rates and orbital periods, as recently observed in GSN~069. Further monitoring of these sources should constrain the parameters of any perturbing companions. This in turn may constrain the nature of the events creating QPE systems, and perhaps give major insights into how the central black holes in low--mass galaxies are able to grow.

We investigate solutions to the TAP equation, a phenomenological implementation of the Theory of the Adjacent Possible. Several implementations of TAP are studied, with potential applications in a range of topics including economics, social sciences, environmental change, evolutionary biological systems, and the nature of physical laws. The generic behaviour is an extended plateau followed by a sharp explosive divergence. We find accurate analytic approximations for the blow-up time that we validate against numerical simulations, and explore the properties of the equation in the vicinity of equilibrium between innovation and extinction. A particular variant, the two-scale TAP model, replaces the initial plateau with a phase of exponential growth, a widening of the TAP equation phenomenology that may enable it to be applied in a wider range of contexts.

Gravitational waves modulate the apparent frequencies of other periodic signals. We propose to use this effect to detect low-frequency gravitational waves by searching for correlated frequency modulations in a large set of well-resolved gravitational wave signals. We apply our proposed method to the large number of gravitational wave signals from Galactic binary white dwarfs that are expected to be detected with the planned space-based gravitational wave detector LISA. We show that, given current projections for the number and properties of these sources and the sensitivity of the instrument, this method would enable the detection of background gravitational wave strain amplitudes of, e.g., $A\simeq10^{-10}$ at a frequency $F\simeq10^{-8}\,\rm Hz$. When using signals from binary neutron stars such as those expected to be observed with proposed detectors like DECIGO, we expect a sensitivity to gravitational waves competitive with that of current Pulsar Timing Arrays. This would allow the detection of gravitational waves from, e.g., super-massive black hole binaries with chirp masses $M_c\gtrsim10^9\,\rm M_\odot$ at a distance $D\simeq10\,\rm Mpc$. Our results show that gravitational-wave detectors could be sensitive at frequencies outside of their designed bandwidth using the same infrastructure. This has the potential to open up unexplored and otherwise inaccessible parts of the gravitational wave spectrum.

In this Perspective we summarize the status of technological development for large-area and low-noise substrate-transferred GaAs/AlGaAs (AlGaAs) crystalline coatings for interferometric gravitational-wave (GW) detectors. These topics were originally presented in a workshop{\dag} bringing together members of the GW community from the laser interferometer gravitational-wave observatory (LIGO), Virgo, and KAGRA collaborations, along with scientists from the precision optical metrology community, and industry partners with extensive expertise in the manufacturing of said coatings. AlGaAs-based crystalline coatings present the possibility of GW observatories having significantly greater range than current systems employing ion-beam sputtered mirrors. Given the low thermal noise of AlGaAs at room temperature, GW detectors could realize these significant sensitivity gains, while potentially avoiding cryogenic operation. However, the development of large-area AlGaAs coatings presents unique challenges. Herein, we describe recent research and development efforts relevant to crystalline coatings, covering characterization efforts on novel noise processes, as well as optical metrology on large-area (~10 cm diameter) mirrors. We further explore options to expand the maximum coating diameter to 20 cm and beyond, forging a path to produce low-noise AlGaAs mirrors amenable to future GW detector upgrades, while noting the unique requirements and prospective experimental testbeds for these novel materials.

Recently, Pei-Ming Ho and Hikaru Kawai have argued that treating particles as wave packets can lead to a shutdown of Hawking radiation at late times near the horizon of black holes. This shutdown arises from viewing quantum field theory near the black hole horizon as an effective field theory, and imposing an appropriate UV cutoff. We show that this effect is also present in the static patch of de Sitter space, leading to a shutdown of Gibbons-Hawking radiation near the de Sitter horizon. Assuming this effect is due to the breakdown of effective field theory, we obtain a bound $t \lesssim H^{-1} \ln (H^{-1} M_P)$ on the time scale of validity of effective field theory in de Sitter space, which matches with the predictions of the Trans-Planckian Censorship Conjecture.

The Nieh-Yan modified teleparallel gravity is a model which modifies the general relativity equivalent teleparallel gravity by a coupling between the Nieh-Yan density and an axion-like field. This model predicts parity violations in the gravitational waves if the axion-like field has a non-trivial background, and more importantly it is ghost free and avoids the pathologies presented in other parity-violating gravity models. The cosmological dynamics and perturbations of the Nieh-Yan modified teleparallel gravity have been investigated in detail, but all these previous investigations rely on the symmetry requirement that in the background universe both the metric and affine connection are homogeneous and isotropic. In this paper we relax the symmetry constraint on the connection and leave it arbitrary at the beginning, after all the cosmological principle only needs the metric of the background spacetime to meet the symmetry requirement. We find a new flat universe solution for the Nieh-Yan modified teleparallel gravity, for which the background dynamics itself is unchanged but the perturbations around it present a new feature that the scalar and tensor perturbations are coupled together at the linear level. The implications of this peculiar feature in primordial perturbations from inflation are also discussed.

Sharjah-Sat-1 is a 3U cubesat with a CdZnTe based hard X-ray detector, called iXRD (improved X-ray Detector) as a scientific payload with the primary objective of monitoring bright X-ray sources in the galaxy. We investigated the effects of the in-orbit background radiation on the iXRD based on Geant4 simulations. Several background components were included in the simulations such as the cosmic diffuse gamma-rays, galactic cosmic rays (protons and alpha particles), trapped protons and electrons, and albedo radiation arising from the upper layer of the atmosphere. The most dominant component is the albedo photon radiation which contributes at low and high energies alike in the instrument energy range of 20 keV - 200 keV. On the other hand, the cosmic diffuse gamma-ray contribution is the strongest between 20 keV and 60 keV in which most of the astrophysics source flux is expected. The third effective component is the galactic cosmic protons. The radiation due to the trapped particles, the albedo neutrons, and the cosmic alpha particles are negligible when the polar regions and the South Atlantic Anomaly region are excluded in the analysis. The total background count rates are ~0.36 and ~0.85 counts/s for the energy bands of 20 - 60 keV and 20 - 200 keV, respectively. We performed charge transportation simulations to determine the spectral response of the iXRD and used it in sensitivity calculations as well. The simulation framework was validated with experimental studies. The estimated sensitivity of 180 mCrab between the energy band of 20 keV - 100 keV indicates that the iXRD could achieve its scientific goals.

This book chapter presents an overview of the historical experimental and theoretical developments in neutrino physics and astrophysics and also the physical properties of neutrinos, as well as the physical processes involving neutrinos. It also discusses the role of neutrinos in astrophysics and cosmology.

We propose a closed-form (i.e. without expansion in the orbital eccentricities) scheme for computations in perturbation theory in the restricted three-body problem (R3BP) when the massless particle is in an orbit exterior to the one of the primary perturber. Starting with a multipole expansion of the barycentric (Jacobi-reduced) Hamiltonian, we carry out a sequence of normalizations in Delaunay variables by Lie series, leading to a secular Hamiltonian model without use of relegation. To this end, we introduce a book-keeping analogous to the one proposed in Cavallari and Efthymiopoulos (2022) for test particle orbits interior to the one of the primary perturber, but here adapted, instead, to the case of exterior orbits. We give numerical examples of the performance of the method in both the planar circular and the spatial elliptic restricted three-body problem, for parameters pertinent to the Sun-Jupiter system. In particular, we demonstrate the method's accuracy in terms of reproducibility of the orbital elements' variations far from mean-motion resonances. As a basic outcome of the method, we show how, using as criterion the size of the series' remainder, we reach to obtain an accurate semi-analytical estimate of the boundary (in the space of orbital elements) where the secular Hamiltonian model arrived at after eliminating the particle's fast degree of freedom provides a valid approximation of the true dynamics.

The emergence of a logically simple solution to the solar neutrino problem based on the hypothesis of the existence of a new interaction involving electron neutrinos and nucleons did not weaken the dominance of the oscillation concept. Therefore, a significant part of the present work is devoted to proving that the basic elements of this concept either do not correspond to the principles of classical logic, or violate the energy-momentum conservation law, or contradict the quantum mechanical basis of coherence, or represent a primitive falsehood. Our analysis concerns successively all stages of the formation of the concept from its conceiving to the assertion about the conversion of the solar electron neutrino into a muon one. When discussing a new fundamental interaction, we note the decisive role in the outcome of the processes of changing the handedness of a neutrino (antineutrino) at each act of its interaction with a real or virtual massless pseudoscalar boson, due to which, at the exit from the Sun, the fluxes of left- and right-handed electron neutrinos become approximately equal. Thanks to the new interaction, beta decays of nuclei have a mode with the emission of a massless pseudoscalar boson, at which the antineutrino changes its handedness and becomes unobservable, what is the essence of the reactor antineutrino anomaly. The nature of the gallium anomaly is similar.

The transcendental expectation of string theory is that the nature of the fundamental forces, particle spectra and masses, together with coupling constants, is uniquely determined by mathematical and logical consistency, non-empirically, that is by pure reason. However pluralism triumphed with the explosive emergence of the multiverse. String theorists have extended a long-sought dream (their unique and final theory) to a landscape or a happy caparnaum. Proponents of string theory try to qualify their arguments via swampland conjectures while cosmologists retreat to their telescopes. We review the current status of the string theory swampland.

Using an adapted version of the SGRID code, we construct for the first time consistent quasi-equilibrium configurations for a binary system consisting of two neutron stars in which each is admixed with dark matter. The stars are modelled as a system of two non-interacting fluids minimally coupled to gravity. For the fluid representing baryonic matter the SLy equation of state is used, whereas the second fluid, which corresponds to dark matter, is described using the equation of state of a degenerate Fermi gas. We consider two different scenarios for the distribution of the dark matter. In the first scenario the dark matter is confined to the core of the star, whereas in the second scenario the dark matter extends beyond the surface of the baryonic matter, forming a halo around the baryonic star. The presence of dark matter alters the star's reaction to the companion's tidal forces, which we investigate in terms of the coordinate deformation and mass shedding parameters. The constructed quasi-equilibrium configurations mark the first step towards consistent numerical-relativity simulations of dark matter admixed neutron star binaries.