Papers for Friday, Dec 10 2021

Distances to the $k$-nearest-neighbor ($k$NN) data points from volume-filling query points are a sensitive probe of spatial clustering. Here we present the first application of $k$NN summary statistics to observational clustering measurement, using the 1000 richest redMaPPer clusters ($0.1\leqslant z\leqslant 0.3$) from the SDSS DR8 catalog. A clustering signal is defined as a difference in the cumulative distribution functions (CDFs) or counts-in-cells functions (CICs) of $k$NN distances from fixed query points to the observed clusters versus a set of unclustered random points. We find that the $k=1,2$-NN CDFs (and CICs) of redMaPPer deviate significantly from the randoms' across scales of 35 to 155 Mpc, which is a robust signature of clustering. In addition to $k$NN, we also measure the two-point correlation function for the same set of redMaPPer clusters versus random points, which shows a noisier and less significant clustering signal within the same radial scales. Quantitatively, the $\chi^2$ distribution for both the $k$NN-CDFs and the two-point correlation function measured on the randoms peak at $\chi^2\sim 50$ (null hypothesis), whereas the $k$NN-CDFs ($\chi^2\sim 300$, $p = 1.54\times 10^{-36}$) pick up a much more significant clustering signal than the two-point function ($\chi^2\sim 100$, $p = 1.16\times 10^{-6}$) when measured on redMaPPer. Finally, the measured 3NN and 4NN CDFs deviate significantly from the predicted $k=3, 4$-NN CDFs assuming an ideal Gaussian field, indicating that redMaPPer clusters trace a non-Gaussian density field which is sensitively picked up by $k$NN summary statistics. Therefore, the $k$NN method serves as a more sensitive probe of clustering complementary to the two point correlation function in sparse (beyond-Gaussian) observational data sets at large scales, providing a novel approach for constraining cosmology and galaxy-halo connection.

The dense central regions of tidally disrupted galaxies can survive as ultra-compact dwarfs (UCDs) that hide among the luminous globular clusters (GCs) in the halo of massive galaxies. An exciting confirmation of this model is the detection of overmassive black holes in the centers of some UCDs, which also lead to elevated dynamical mass-to-light ratios ($M/L_{dyn}$). Here we present new high-resolution spectroscopic observations of 321 luminous GC candidates in the massive galaxy NGC 5128/Centaurus A. Using these data we confirm 27 new luminous GCs, and measure velocity dispersions for 57 luminous GCs (with $g$-band luminosities between $2.5 \times 10^5$ and $2.5 \times 10^7 L_{\odot}$), of which 48 have no previous reliable measurements. Combining these data with size measurements from Gaia, we determine the $M/L_{dyn}$ for all 57 luminous GCs. We see a clear bimodality in the $M/L_{dyn}$ distribution, with a population of normal GCs with mean $M/L_{dyn}=1.51\pm0.31$, and a second population of $\sim$20 GCs with elevated mean $M/L_{dyn}=2.68\pm0.22$. We show that black holes with masses $\sim4$-18% of the luminous GCs can explain the elevated mass-to-light ratios. Hence, it is plausible that the NGC 5128 sources with elevated $M/L_{dyn}$ are mostly stripped galaxy nuclei that contain massive central black holes, though future high spatial resolution observations are necessary to confirm this hypothesis for individual sources. We also present a detailed discussion of an extreme outlier, VHH81-01, one of the largest and most massive GC in NGC 5128, making it an exceptionally strong candidate to be a tidally stripped nucleus.

Identifying very high redshift galaxies is crucial for understanding the formation and evolution of galaxies. However, nowadays many questions remain and the uncertainty on the Epoch of Reionization is large. In this approach, some models allow a double reionization scenario, although the number of confirmed detections at very high-$z$ is still scarce to stand as observational proof. The main goal of this project is to study the feasibility of searching for Lyman-$\alpha$ Emitters (LAEs) at $z \sim 9$ using a narrow-band (NB) filter designed specifically by our team and built for this experiment. We make use of the NB technique to select candidates by measuring the flux excess due to the Ly$\alpha$ emission. The observations were taken with a NB filter (FWHM = 11 nm and central wavelength $\lambda_{c} = 1.257 \mu$m) and the CIRCE near-infrared camera for the GTC telescope. We describe a data reduction procedure specially optimized to minimize the instrumental effects. With a total exposure time of 18.3 hours, the final NB image covers an area of $\sim 6.7$ arcmin$^{2}$, which corresponds to a comoving volume of $1.1 \times 10^{3}$ Mpc$^{3}$ at $z = 9.3$. We push to the limit the sources detection which allows us to analyze an initial sample of roughly one hundred objects. We detail the different criteria applied, including visual checks in different photometric bands, for the candidate selection. Notwithstanding, none of the objects resembled a reliable LAE and we did not find any robust candidate down to an emission-line flux of $2.9 \times 10^{-16}$ erg s$^{-1}$ cm$^{-2}$, which corresponds to a Ly$\alpha$ luminosity limit of $3 \times 10^{44}$ erg s$^{-1}$. We derive an upper limit on the Ly$\alpha$ luminosity function at $z \sim 9$ in good agreement with previous constraints. We conclude that deeper and wider surveys are needed to study the LAE population at the cosmic dawn.

The galaxy population is strongly bimodal in both colour and morphology, and the two measures correlate strongly, with most blue galaxies being late-types (spirals) and most early-types, typically ellipticals, being red. This observation has led to the use of colour as a convenient selection criteria to make samples which are then labelled by morphology. Such use of colour as a proxy for morphology results in necessarily impure and incomplete samples. In this paper, we make use of the morphological labels produced by Galaxy Zoo to measure how incomplete and impure such samples are, considering optical (ugriz), NUV and NIR (JHK) bands. The best single colour optical selection is found using a threshold of g-r = 0.742, but this still results in a sample where only 56% of red galaxies are smooth and 56% of smooth galaxies are red. Use of the NUV gives some improvement over purely optical bands, particularly for late-types, but still results in low purity/completeness for early-types. No significant improvement is found by adding NIR bands. With any two bands, including NUV, a sample of early-types with greater than two-thirds purity cannot be constructed. Advances in quantitative galaxy morphologies have made colour-morphology proxy selections largely unnecessary going forward; where such assumptions are still required, we recommend studies carefully consider the implications of sample incompleteness/impurity.

We use \texttt{GRUMPY}, a simple regulator-type model for dwarf galaxy formation and evolution, to forward model dwarf galaxy satellite population of the Milky Way (MW) using the Caterpillar zoom-in simulation suite. We show that luminosity and distance distributions of the model satellites are consistent with the distributions measured in the DES, PS1 and SDSS surveys, even without including a model for the orphan galaxies. We also show for the first time that our model for dwarf galaxy sizes can reproduce both the observed {\it distribution} of stellar half-mass radii, $r_{1/2}$, of the MW satellites and the overall $r_{1/2}-M_\star$ relation exhibited by observed dwarf galaxies. The model predicts that some of the observed faint stellar systems with $r_{1/2}<10$ pc are ultra-faint dwarf galaxies. Scaling of the stellar mass $M_\star$ and peak halo mass $M_{\rm peak}$ for the model satellites is not described by a power law, but has a clear flattening of $M_\star-M_{\rm peak}$ scaling at $M_{\rm peak}<10^8\,M_\odot$ imprinted by reionization. As a result, the fraction of low mass haloes ($M_{\rm peak} < 10^8 M_\odot$) hosting galaxies with $M_V<0$ is predicted to be 50\% at $M_{\rm peak} \sim 3.6 \times 10^7\,M_\odot$. We find that such high fraction at that halo mass is in fact required to explain the number of dwarf galaxies discovered recently in the HSC-SSP survey. Using the model we forecast that there should be the total of $440^{+201}_{-147}$ MW satellites with $M_V < 0$ and $r_{1/2} > 10$ pc within 300 kpc and make specific predictions for the HSC-SSP, DELVE-WIDE and LSST surveys.

Magnetic fields play a vital role in numerous astrophysical processes such as star formation and the interstellar medium. In particular, their role in the formation and evolution of galaxies is not well understood. This paper presents high-resolution magnetohydrodynamic (MHD) simulations performed with GIZMO to investigate the effect of magnetic fields on primordial galaxy formation. Physical processes such as relevant gas physics (e.g., gas cooling and gas chemistry), star formation, stellar and supernova feedback, and chemical enrichment were considered in the simulations. The simulation results suggest that cosmic magnetic fields can be amplified from 1e-13 G to a few microgauss during cosmic structure evolution and galaxy formation. In the ideal MHD setting, in primordial galaxies at z>8, the magnetic energy is less than the thermal and kinetic energy, and therefore, magnetic fields hardly affect the gas dynamics and star formation in these galaxies. Specifically, the consideration of micro-physics properties such as metal diffusion, heat conduction, and viscosity in the MHD simulations, could increase the magnetic field strength. Notably, metal diffusion reduced gas cooling by decreasing the metallicity and thereby suppresses star formation in the primordial galaxies. As a result, the cosmic re-ionization driven by these primordial galaxies may be delayed.

We report the first study to characterise intranight variability of the blazar class from the perspective of (rest-frame) UV emission. For this, we carried out intranight optical monitoring of 14 flat-spectrum radio quasars (FSRQs) located at high redshifts (1.5 < $z$ < 3.7), in 42 sessions of median duration $\sim$ 5.4 hr. These sources were grouped into two samples distinguished by published fractional optical polarisation: (i) nine low-polarisation sources with $p_{opt} < 3\%$ and (ii) five high-polarisation sources. Unexpectedly, a high duty cycle (DC $\sim$ 30$\%$) is found for intranight variability (with amplitude $\psi > 3\%$) of the low-polarisation sources. This DC is a few times higher than that reported for low-polarisation FSRQs located at moderate redshifts ($z$ $\sim$ 0.7) and hence typically monitored in the rest-frame blue-optical. Further, we found no evidence for an increased intranight variability of UV emission with polarisation, in contrast to the strong correlation found for intranight variability of optical emission. We briefly discuss this in the context of an existing scenario which posits that the nonthermal UV emission of blazars arises from a relativistic particle population different from that radiating up to near-infrared/optical frequencies.

In recent years it has been noted that the perturbative treatment of the statistics of fluctuations may fail to make correct predictions for the abundance of primordial black holes (PBHs). Moreover, it has been shown in some explicit single-field examples that the nonperturbative effects may lead to an exponential tail for the probability distribution function (PDF) of fluctuations responsible for PBH formation -- in contrast to the PDF being Gaussian, as suggested by perturbation theory. In this paper, we advocate that the so-called $\delta N$ formalism can be considered as a simple, yet effective, tool for the nonperturbative estimate of the tail of the PDF. We discuss the criteria a model needs to satisfy so that the results of the classical $\delta N$ formalism can be trusted and most possible complications due to the quantum nature of fluctuations can be avoided. As a proof of concept, we then apply this method to a simple example and show that the tail of the PDF can be even heavier than exponential, leading to a significant enhancement of the PBH formation probability, compared with the predictions of the perturbation theory. Our results, along with other related findings, motivate invention of new, nonperturbative methods for the problem and open up new ideas on generating PBHs with notable abundance.

The observed magnifications and light curves of the quadruply-imaged iPTF16geu supernova (SN) offers a unique opportunity to study a lens system with a variety of independent constraints. The four observed positions can be used to constrain the macrolens model. The magnifications and light curves at the four SN positions are more useful to constrain microlensing models. We define the macrolens model as a combination of a baryonic component that traces the observed light distribution, and a dark matter halo component. We constrain the macrolens model using the positional constraints given by the 4 observed images, and compare it with the best model obtained when magnification constraints are included. We find that the magnification can not be explained by a macrolens model alone, and that contributions from substructures such as microlenses are needed to explain the observed magnifications. We consider microlens models based on the inferred stellar mass from the baryonic component of the macrolens model, and use the observed magnification and light curves to constrain the contribution from microlenses. We compute the likelihood of a variety of macro+micro lens models where we vary the dark matter halo, baryonic component, and microlens configurations. We use information about the position, magnification and, for the first time, the lightcurves of the four observed SN images. We combine macrolens and microlens models in order to reproduce the observations; the four SN positions, magnifications, and lack of fluctuations in the light curves. After marginalizing over the model parameters, we find that larger stellar surface mass densities are preferred. This result suggests that the mass of the baryonic component is dominated by its stellar component. We conclude that microlensing from the baryonic component suffices to explain the observed flux ratios and light curves.

We investigate the effect of Dark Stars (DSs) on the reionization history of the Universe, and the interplay between them and feedback due to Lyman-Werner (LW) radiation in reducing the Cosmic Microwave Background (CMB) optical depth to a value within the $\tau = 0.054 \pm 0.007$ range measured by Planck. We use a semi-analytic approach to evaluate reionization histories and CMB optical depths, which includes Population II (Pop II) stars in atomic cooling halos and Pop III stars in minihalos with LW feedback, preceded by a DS phase. We show that while LW feedback by itself can reduce the integrated optical depth to the last scattering surface to $\sim 0.05$ only if the Pop III star formation efficiency is less than $\sim 0.2\%$, the inclusion of a population of DSs can naturally lead to the measured CMB optical depth for much larger Pop III star formation efficiencies $\gtrsim 1\%$.

Chemical models predict that in cold cores gas-phase methanol is expected to be abundant at the outer edge of the CO depletion zone, where CO is actively adsorbed. CO adsorption correlates with volume density in cold cores, and, in nearby molecular clouds, the catastrophic CO freeze-out happens at volume densities above 10$^4$ cm$^{-3}$. The methanol production rate is maximized there and its freeze-out rate does not overcome its production rate, while the molecules are shielded from UV destruction by gas and dust. Thus, in cold cores, methanol abundance should generally correlate with visual extinction that depends both on volume and column density. In this work, we test the most basic model prediction that maximum methanol abundance is associated with a local $A_V\simeq$4 mag in dense cores and constrain the model parameters with the observational data. With the IRAM 30 m antenna, we mapped the CH$_3$OH (2-1) and (3-2) transitions toward seven dense cores in the L1495 filament in Taurus to measure the methanol abundance. We use the Herschel/SPIRE maps to estimate visual extinction, and the C$^{18}$O(2-1) maps from Tafalla & Hacar (2015) to estimate CO depletion. We explored the observed and modeled correlations between the methanol abundances, CO depletion, and visual extinction varying the key model parameters. The modeling results show that hydrogen surface diffusion via tunneling is crucial to reproduce the observed methanol abundances, and the needed reactive desorption efficiency matches the one deduced from laboratory experiments.

More than 500 diffuse interstellar bands (DIBs) have been observed in astronomical spectra, and their signatures and correlations in different environments have been studied over the past decades to reveal clues about the nature of the carriers. We compare the equivalent widths of the DIBs, normalized to the amount of reddening, E_B-V, to search for anti-correlated DIB pairs using a data sample containing 54 DIBs measured in 25 sight lines. This data sample covers most of the strong and commonly detected DIBs in the optical region, and the sight lines probe a variety of ISM conditions. We find that 12.9% of the DIB pairs are anti-correlated, and the lowest Pearson correlation coefficient is r_norm ~ -0.7. We revisit correlation-based DIB families and are able to reproduce the assignments of such families for the well-studied DIBs by applying hierarchical agglomerative and k-means clustering algorithms. We visualize the dissimilarities between DIBs, represented by 1 - r_norm, using multi-dimensional scaling (MDS). With this representation, we find that the DIBs form a rather continuous sequence, which implies that some properties of the DIB carriers are changing gradually following this sequence. We also find at that least two factors are needed to properly explain the dissimilarities between DIBs. While the first factor may be interpreted as related to the ionization properties of the DIB carriers, a physical interpretation of the second factor is less clear and may be related to how DIB carriers interact with surrounding interstellar material.

The observations of the near-infrared excess object G2/DSO induced an increased attention towards the Galactic center and its vicinity. The predicted flaring event in 2014 and the outcome of the intense monitoring of the supermassive black hole in the center of our Galaxy did not fulfill all predictions about a significantly enhanced accretion event. Subsequent observations furthermore addressed the question concerning the nature of the object because of its compact shape, especially during its periapse in 2014. Theoretical approaches have attempted to answer the contradicting behavior of the object, resisting the expected dissolution of a gaseous cloud due to tidal forces in combination with evaporation and hydrodynamical instabilities. However, assuming that the object is rather a dust-enshrouded young stellar object seems to be in line with the predictions of several groups and observations presented in numerous publications. Here we present a detailed overview and analysis of the observations of the object that have been performed with SINFONI (VLT) and provide a comprehensive approach to clarify the nature of G2/DSO. We show that the tail emission consists of two isolated and compact sources with different orbital elements for each source rather than an extended and stretched component as it appeared in previous representations of the same data. Considering our recent publications, we propose that the monitored dust-enshrouded objects are remnants of a dissolved young stellar cluster whose formation was initiated in the Circum-nuclear Disk. This indicates a shared history which agrees with our analysis of the D- and X-sources.

GW170817 is the only gravitational-wave (GW) event, for which a confirmed {\gamma}-ray counterpart, GRB 170817A, has been detected. Here we present a method to search for another type of {\gamma}-ray signal, a {\gamma}-ray burst precursor, associated with a compact binary merger. If emitted shortly before the coalescence, a high-energy electromagnetic (EM) flash travels through a highly dynamical and relativistic environment, created by the two compact objects orbiting each other. Thus, the EM signal arriving at an Earth observer could present a somewhat predictable time-dependent modulation. We describe a targeted search method for lightcurves exhibiting such a modulation, parameterized by the observer-frame component masses and binary merger time, using Fermi-GBM data. The sensitivity of the method is assessed based on simulated signals added to GBM data. The method is then applied to a selection of potentially interesting compact binary mergers detected during the second (O2) and third (O3) observing runs of Advanced LIGO and Advanced Virgo. We find no significant modulated {\gamma}-ray precursor signal associated with any of the considered events.

We present a novel magnetohydrostatic numerical model that solves directly for the force-balanced magnetic field in the solar corona. This model is constructed with Radial Basis Function Finite Differences (RBF-FD), specifically 3D polyharmonic splines plus polynomials, as the core discretization. This set of PDEs is particularly difficult to solve since in the limit of the forcing going to zero it becomes ill-posed with a multitude of solutions. For the forcing equal to zero there are no numerically tractable solutions. For finite forcing, the ability to converge onto a physically viable solution is delicate as will be demonstrated. The static force-balance equations are of a hyperbolic nature, in that information of the magnetic field travels along characteristic surfaces, yet they require an elliptic type solver approach for a sparse overdetermined ill-conditioned system. As an example, we reconstruct a highly nonlinear analytic model designed to represent long-lived magnetic structures observed in the solar corona.

We report a model study on the effects of clouds on emission spectra of super-Venus planets. Our goal is to assess possible ways to identify characteristic spectral features due to clouds. We show that it is possible to distinguish an impact of H2SO4 clouds on the CO2 absorption band at 4.8 micron for temperature profiles with and without a thermal inversion. The thermal inversion can help to distinguish the signal from high altitude clouds (85 km, ~1 mbar). Featureless emission spectra are found for high altitude clouds (85 km, ~1 mbar) with temperature profile without thermal inversion. More spectral features appear in the emission spectra with decreasing cloud top altitudes. The compactness of clouds has an inverse effect on emission spectra than cloud top altitudes. Small cloud scale heights reduce the signal and the CO2 absorption bands become flat.

We present H-band light curves of Milky Way Classical Cepheids observed as part of the DEHVILS survey with the Wide-Field Infrared Camera on the United Kingdom InfraRed Telescope. Due to the crowded nature of these fields caused by defocusing the Camera, we performed difference-imaging photometry by modifying a pipeline originally developed to analyze images from the Transiting Exoplanet Survey Satellite. We achieved a photometric precision in line with expectations from photon statistics, reaching 0.01 mag for 8 <= H <= 11 mag. We used the resulting Cepheid light curves to derive corrections to "mean light" for random-phase Hubble Space Telescope observations in F160W. We find good agreement with previous phase corrections based on VI light curves from the literature, with a mean difference of -1 +/- 6 millimag.

We study the scenario of Kanadiakis horizon entropy cosmology which arises from the application of the gravity-thermodynamics conjecture using the Kaniadakis modified entropy. The resulting modified Friedmann equations contain extra terms that constitute an effective dark energy sector. We use data from Cosmic chronometers, Supernova Type Ia, HII galaxies, Strong lensing systems, and Baryon acoustic oscillations observations and we apply a Bayesian Markov Chain Monte Carlo analysis to construct the likelihood contours for the model parameters. We find that the Kaniadakis parameter is constrained around 0, namely, around the value where the standard Bekenstein-Hawking is recovered. Concerning the normalized Hubble parameter, we find $h=0.708^{+0.012}_{-0.011}$, a result that is independently verified by applying the $\mathbf{\mathbb{H}}0(z)$ diagnostic and, thus, we conclude that the scenario at hand can alleviate the $H_0$ tension problem. Regarding the transition redshift, the reconstruction of the cosmographic parameters gives $z_T=0.715^{+0.042}_{-0.041}$. Lastly, we perform a phase-space analysis, and we show that the Universe past attractor is the matter-dominated epoch, while at late times the Universe results in the dark-energy-dominated solution.

At least two active plumes were observed on Neptune's moon Triton during the Voyager 2 flyby in 1989. Models for Triton's plumes have previously been grouped into five hypotheses, two of which are primarily atmospheric phenomena and are generally considered unlikely, and three of which include eruptive processes and are plausible. These hypotheses are compared, including new arguments, such as comparisons based on current understanding of Mars, Enceladus, and Pluto. An eruption model based on a solar-powered, solid-state greenhouse effect was previously considered the leading hypothesis for Triton's plumes, in part due to the proximity of the plumes to the subsolar latitude during the Voyager 2 flyby and the distribution of Triton's fans that are putatively deposits from former plumes. The other two eruption hypotheses are powered by internal heat, not solar insolation. Based on new analyses of the ostensible relation between the latitude of the subsolar point on Triton and the geographic locations of the plumes and fans, we argue that neither the locations of the plumes nor fans are strong evidence in favor of the solar-powered hypothesis. We conclude that all three eruption hypotheses should be considered further. Five tests are presented that could be implemented with remote sensing observations from future spacecraft to confidently distinguish among the eruption hypotheses for Triton's plumes. The five tests are based on the: (1) composition and thickness of Triton's southern hemisphere terrains, (2) composition of fan deposits, (3) distribution of active plumes, (4) distribution of fans, and (5) surface temperature at the locations of plumes and/or fans. The tests are independent, but complementary, and implementable with a single flyby mission such as the Trident mission concept. We note that, in the case of the solar-driven hypothesis, the 2030s and 2040s may be the last ...

The diffuse $\gamma$-ray was measured up to 957 TeV by the Tibet-AS$\gamma$ experiment. Presuming it is produced by the hadronic interaction between cosmic ray nuclei and the interstellar medium, it requires that the cosmic ray nuclei should be accelerated well beyond PeV energies. However, measurements of the spectrum of proton and Helium by a few experiments show break below PeV. To solve this apparent discrepancy, we propose in this work that a new structure of cosmic rays may exist beyond PeV, which can contribute to the highest energy diffuse $\gamma$ rays. This additional component may serve as another population of Galactic cosmic ray accelerators, and can contribute to the cosmic ray fluxes beyond the second knee. Future measurements of the energy spectra of different nuclei species may test the existence of this new component.

X-ray emission provides the most direct diagnostics of the energy-release process in solar flares. Occasionally, a superhot X-ray source is found to be above hot flare loops of ~10 MK temperature. While the origin of the superhot plasma is still elusive, it has conjured up an intriguing image of in-situ plasma heating near the reconnection site high above the flare loops, in contrast to the conventional picture of chromospheric evaporation. Here we investigate an extremely long-duration solar flare, in which EUV images show two distinct flare loop systems that appear successively along a Gamma-shaped polarity inversion line (PIL). When both flare loop systems are present, the HXR spectrum is found to be well fitted by combining a hot component (Te ~12 MK) and a superhot component (Te ~30 MK). Associated with a fast CME, the superhot X-ray source is located at top of the flare arcade that appears earlier, straddling and extending along the long "arm" of the Gamma-shaped PIL. Associated with a slow CME, the hot X-ray source is located at the top of the flare arcade that appears later and sits astride the short "arm" of the Gamma-shaped PIL. Aided by observations from a different viewing angle, we are able to verify that the superhot X-ray source is above the hot one in projection, but the two sources belong to different flare loop systems. Thus, this case study provides a stereoscopic observation explaining the co-existence of superhot and hot X-ray emitting plasmas in solar flares.

Low luminosity dwarf galaxies provide stringent constraints on the nature of dark matter. Establishing these constraints depends on precise kinematic measurements of individual stars. In this overview for non-specialists, we describe current and future prospects for three unique tests of dark matter using resolved stellar kinematics in low luminosity galaxies: the overall number of satellite galaxies around the Milky Way, dark-matter annihilation radiation from dwarf galaxies, and their internal density profiles. We then assess the prospects for meaningfully testing theories of dark matter based on the improved kinematic precision expected from upcoming facilities.

Rocky planets are common around other stars, but their atmospheric properties remain largely unconstrained. Thanks to a wealth of recent planet discoveries and upcoming advances in observing capability, we are poised to characterize the atmospheres of dozens of rocky exoplanets in this decade. Theoretical understanding of rocky exoplanet atmospheres has advanced considerably in the last few years, yielding testable predictions of their evolution, chemistry, dynamics and even possible biosignatures. Here we review key progress in this field to date and discuss future objectives. Our major conclusions are: 1) Many rocky planets may form with initial H$_2$-He envelopes that are later lost to space, likely due to a combination of stellar UV/X-ray irradiation and internal heating. 2) After the early stages of evolution, a wide diversity of atmospheric compositions is expected, due to variations in host star flux, atmospheric escape rates, interior exchange and other factors. 3) Observations have ruled out the presence of hydrogen-dominated atmospheres on several nearby rocky exoplanets, and the presence of any thick atmosphere on one target. More detailed atmospheric characterization of these planets and others will become possible in the near future. 4) Exoplanet biosphere searches are an exciting future goal. However, reliable detections for a representative sample of planets will require further advances in observing capability and improvements in our understanding of abiotic planetary processes.

Dust emission was detected on main-belt asteroid 596 Scheila in December 2010, and attributed to the collision of a few-tens-of-meters projectile on the surface of the asteroid. In such impact, the ejected material from the collided body is expected to mainly comes from its fresh, unweathered subsurface. Therefore, it is expected that the surface of 596 was partially or entirely refreshed during the 2010 impact. By combining spectra of 596 from the literature and our own observations, we show that the 2010 impact event resulted in a significant slope change in the near-infrared (0.8 to 2.5 {\mu}m) spectrum of the asteroid, from moderately red (T-type) before the impact to red (D-type) after the impact. This provides evidence that red carbonaceous asteroids become less red with time due to space weathering, in agreement with predictions derived from laboratory experiments on the primitive Tagish Lake meteorite, which is spectrally similar to 596. This discovery provides the very first telescopic confirmation of the expected weathering trend of asteroids spectrally analog to Tagish Lake and/or anhydrous chondritic porous interplanetary dust particles. Our results also suggest that the population of implanted objects from the outer solar system is much larger than previously estimated in the main-belt, but many of these objects are hidden below their space-weathered surface.

Through the Backyard Worlds: Planet 9 citizen science project we discovered a late-type L dwarf co-moving with the young K0 star BD+60 1417 at a projected separation of 37" or 1662 AU. The secondary - CWISER J124332.12+600126.2 (W1243) - is detected in both the CatWISE2020 and 2MASS reject tables. The photometric distance and CatWISE proper motion both match that of the primary within ~1sigma and our estimates for chance alignment yield a zero probability. Follow-up near infrared spectroscopy reveals W1243 to be a very red 2MASS color(J-Ks=2.72), low-surface gravity source that we classify as L6 - L8gamma. Its spectral morphology strongly resembles that of confirmed late-type L dwarfs in 10 - 150 Myr moving groups as well as that of planetary mass companions. The position on near- and mid-infrared color-magnitude diagrams indicates the source is redder and fainter than the field sequence, a telltale sign of an object with thick clouds and a complex atmosphere. For the primary we obtained new optical spectroscopy and analyzed all available literature information for youth indicators. We conclude that the Li I abundance, its loci on color-magnitude and color-color diagrams, and the rotation rate revealed in multiple TESS sectors are all consistent with an age of 50 - 150 Myr. Using our re-evaluated age of the primary, the Gaia parallax along with the photometry and spectrum for W1243 we find a Teff=1303+/-31 K, logg=4.3+/-0.17 cm s-2, and a mass of 15+/-5 MJup. We find a physical separation of ~1662 AU and a mass ratio of ~0.01 for this system. Placing it in context with the diverse collection of binary stars, brown dwarf and planetary companions, the BD+60 1417 system falls in a sparsely sampled area where the formation pathway is difficult to assess.

We have determined the amount of stellar mass segregation in over 50 globular clusters and ultra-faint dwarf galaxy candidates based on deep HST and ground-based photometry. We find that the amount of mass segregation in globular clusters is strongly correlated with their relaxation time and that all clusters with relaxation times of the order of their ages or longer have little to no mass segregation. For each cluster, the amount of mass segregation seen is fully compatible with the amount expected by dynamical evolution from initially unsegregated clusters, showing that globular clusters formed without primordial mass segregation among their low-mass stars. Ultra-faint dwarf galaxy candidates split into two groups, star clusters which follow the same trend between relaxation time and amount of mass segregation as globular clusters and dark-matter dominated dwarf galaxies that are unsegregated despite having relaxation times smaller than a Hubble time. Stellar abundance and velocity dispersion data, where available, confirm our classification. After classification of the ultra-faint dwarf galaxy candidates, we find that outer halo star clusters have average densities inside their half-light radii of 0.03 M$_\odot$/pc$^3 \lesssim \rho_h \lesssim$ 1 M$_\odot$/pc$^3$, while dwarf galaxies have stellar densities of 0.001 M$_\odot$/pc$^3 \lesssim \rho_h \lesssim $ 0.03 M$_\odot$/pc$^3$. The reason for this separation in density is most likely a combination of the initial conditions by which the systems formed and the requirement to withstand external tidal forces.

The transit timing variation (TTV) and transmission spectroscopy analyses of the planet HAT-P-37b, which is a hot Jupiter orbiting an G-type star, were performed. Nine new transit light curves are obtained and analysed together with 21 published light curves from the literature. The updated physical parameters of HAT-P-37b are presented. The TTV analyses show a possibility that the system has an additional planet which induced the TTVs amplitude signal of 1.74 $\pm$ 0.17 minutes. If the body is located near the 1:2 mean motion resonance orbit, the sinusoidal TTV signal could be caused by the gravitational interaction of a sub-Earth mass planet with mass of 0.06 $M_\oplus$. From the analysis of an upper mass limit for the second planet, the Saturn mass planet with orbital period less than 6 days is excluded. The broad-band transmission spectra of HAT-P-37b favours a cloudy atmospheric model with an outlier spectrum in $B$-filter.

We observed GRB190114C (redshift z = 0.4245), the first GRB ever detected at TeV energies, at optical and near-infrared wavelengths with several ground-based telescopes and the Hubble Space Telescope, with the primary goal of studying its underlying supernova, SN2019jrj. The monitoring spanned the time interval between 1.3 and 370 days after the burst, in the observer frame. We find that the afterglow emission can be modelled with a forward shock propagating in a uniform medium modified by time-variable extinction along the line of sight. A jet break could be present after 7 rest-frame days, and accordingly the maximum luminosity of the underlying SN ranges between that of stripped-envelope corecollapse supernovae (SNe) of intermediate luminosity, and that of the luminous GRB-associated SN2013dx. The observed spectral absorption lines of SN2019jrj are not as broad as in classical GRB-SNe, and are rather more similar to those of less-luminous core-collapse SNe. Taking the broad-lined stripped-envelope core-collapse SN2004aw as an analogue, we tentatively derive the basic physical properties of SN2019jrj. We discuss the possibility that a fraction of the TeV emission of this source might have had a hadronic origin and estimate the expected high-energy neutrino detection level with IceCube.

The effects of cosmic ray diffusion and radiative cooling on the structure of the Galactic wind are studied in steady state approximation. It is known that realistic cooling processes suppress the wind from launching. The effects of cosmic ray diffusion is also supposed to be unfavorable for launching the wind. Both of these effects have not been studied simultaneously in a steady state approximation of the wind. We find 327254 solutions of the steady state Galactic wind, and confirm that the effect of cosmic ray pressure depends on the Alfv\'en Mach number, mass flux carried by the wind does not depend on the cosmic ray pressure directly (but depend on the thermal pressure), and typical condition found in the Galaxy may correspond to the wind solution that provide a metal polluted matters at a height of $\sim300$ kpc from the disk.

Background The Gravitational wave high-energy Electromagnetic Counterpart All-sky Monitor (GECAM) is primarily designed to spot gamma-ray bursts corresponding to gravitational waves. In order to achieve stable observations from various astronomical phenomena, the payload performance need to be monitored during the in-orbit operation. Method This article describes the design and implementation of GECAM satellite payload performance monitoring (GPPM) software. The software extracts the payload status and telescope observations (light curves, energy spectrums, characteristic peak fitting of energy spectrums, etc) from the payload data. Considering the large amount of payload status parameters in the engineering data, we have designed a method of parameter processing based on the configuration tables. This method can deal with the frequent changes of the data formats and facilitate program maintenance. Payload status and performance are monitored through defined thresholds and monitoring reports. The entire software is implemented in python language and the huge amount of observation data is stored in MongoDB. Conclusion The design and implementation of GPPM software have been completed, tested with ground and in-orbit payload data. The software can monitor the performance of GECAM payload effectively. The overall design of the software and the data processing method can be applied to other satellites.

In the local Universe, the efficiency for converting baryonic gas into stars is very low. In dark matter halos where galaxies form and evolve, the average efficiency varies with galaxy stellar mass and has a maximum of about twenty percent for Milky-Way-like galaxies. The low efficiency at higher mass is believed to be produced by some quenching processes, such as the feedback from active galactic nuclei. We perform an analysis of weak lensing and satellite kinematics for SDSS central galaxies. Our results reveal that the efficiency is much higher, more than sixty percent, for a large population of massive star-forming galaxies around $10^{11}\ \rm M_\odot$. This suggests that these galaxies acquired most of the gas in their halos and converted it into stars without being affected significantly by quenching processes. This population of galaxies is not reproduced in current galaxy formation models, indicating that our understanding of galaxy formation is incomplete. The implications of our results on circumgalactic media, star formation quenching and disc galaxy rotation curves are discussed. We also examine systematic uncertainties in halo-mass and stellar-mass measurements that might influence our results.

We study the inflationary implications of a novel parity-violating gravity model, which modifies the teleparallel equivalent of general relativity by introducing the Nieh-Yan term coupled to an axion-like field. The parity-violating Nieh-Yan term results in the velocity birefringence of gravitational waves (GWs) and triggers the tachyonic instability only for one of the two circular polarization states. We consider that the inflaton is identified as the coupled axion-like field with a wiggly potential characterized by steep cliffs connected by smooth plateaus. During inflation, the temporary fast roll of axion on the cliff-like region leads to the significant enhancement of the tensor perturbations in one polarization state with the wave numbers that exit the horizon around this period. In this setup, the resulting energy spectrum for GWs presents a sizable localized bump involving the contribution of only one polarization state. This chiral GW background is detectable by LISA and Taiji, and its chirality can be determined by correlating two detectors, which provide an opportunity to probe the inflation and test the gravity model.

Bright-rimmed clouds (BRCs) are ideal candidates to study radiation-driven implosion mode of star formation as they are potential sites of triggered star formation, located at the edges of H{\sc ii} regions, showing evidence of ongoing star formation processes. BRC 18 is located towards the eastern edge of relatively closer ($\sim$400 pc) H{\sc ii} region excited by $\lambda$ Ori. We made R-band polarimetric observations of 17 candidate young stellar objects (YSOs) located towards BRC 18 to investigate any preferred orientation of the discs with respect to the ambient magnetic field and the direction of energetic photons from $\lambda$ Ori. We found that the discs are oriented randomly with respect to the projected magnetic field. Using distances and proper motions from the \textit{Gaia} EDR3 of the candidate YSOs, we investigated the possible acceleration of BRC 18, away from $\lambda$ Ori due to the well known "Rocket Effect", by assuming that both the candidate YSOs and BRC 18 are kinematically coupled. The relative proper motions of the candidate YSOs are found to show a trend of moving away from $\lambda$ Ori. We computed the offset between the angle of the direction of the ionization front and the relative proper motion of the candidate YSOs and found it to lie close to being parallel to each other. Additionally, we found 12 sources that are comoving with the known candidate YSOs towards BRC 18. These comoving sources are most likely to be young and are missed in previous surveys conducted to identify potential YSOs of the region.

Astrometric satellite \textit{Gaia} is expected to observe non-interacting black hole (BH) binaries with luminous companions (LCs) (hereafter BH-LC binaries), a different population from BH X-ray binaries previously discovered. The detectability of BH-LC binaries with \textit{Gaia} might be dependent on binary evolution models. We investigated the \textit{Gaia}'s detectability of BH-LC binaries formed through isolated binary evolution by means of binary population synthesis technique, and examined its dependence on single and binary star models: supernova models, common envelope (CE) ejection efficiency $\alpha$, and BH natal kick models. We estimated that $1.1$ -- $46$ BH-LC binaries can be detected within five-year observation, and found that $\alpha$ has the largest impacts on the detectable number. In each model, observable and intrinsic BH-LC binaries have similar distributions. Therefore, we found three important implications: (1) if the lower BH mass gap is not intrinsic (i.e. $3$ -- $5 M_\odot$ BHs exist), \textit{Gaia} will observe $\leq 5 M_\odot$ BHs, (2) we may observe short orbital period binaries with light LCs if CE efficiency is significantly high, and (3) we may be able to identify the existence of natal kick from eccentricity distribution.

We study near-infrared (JHK) and X-ray light curves of Cyg X-3 obtained with the 2.5-m telescope of the Caucasian Mountain Observatory of MSU SAI and collected from RXTE ASM and MAXI archives. The light curves in the X-ray and IR domains are strongly affected by irregular variations. However, the mean curves are remarkably stable and qualitatively similar in both domains. This means that the IR flux of the system originates not only from the free-free radiation of the WR wind but also from a compact IR source located near the relativistic companion. The shape of the mean X-ray and IR light curves suggest the existence of two additional structures in the WR wind - a bow shock near the relativistic companion and a so-called "clumpy trail" (Vilhu et al. 2013). Modeling of the mean X-ray and IR light curves allowed us to obtain important system parameters: the orbital phase of the superior conjunction of the relativistic companion $\phi_0=-0.066\pm 0.006$, the orbital inclination angle $i=29.5^\circ\pm 1.2^\circ$, and the WR mass-loss rate $\dot{M} = (0.96\pm 0.14)\times 10^{-5}\rm M_\odot yr^{-1}$. By using relations between $\dot{M}$ and the rate of the period change and between $\dot{M}$ and the WR mass, we estimated the probable mass of the relativistic companion $M_{\rm C}\simeq 7.2\rm M_\odot$ which points towards the black hole hypothesis. However, this estimate is based on the assumption of a smooth WR wind. Considering the uncertainty associated with clumping, the mass-loss rate can be lower which leaves room for the neutron star hypothesis.

Solar flares are often accompanied by filament/prominence eruptions ($\sim10^{4}$ K and $\sim 10^{10-11}$ cm$^{-3}$), sometimes leading to coronal mass ejections (CMEs) that directly affect the Earth's environment. `Superflares' are found on some active solar-type (G-type main-sequence) stars, but the association of filament eruptions/CMEs has not been established. Here we show that our optical spectroscopic observation of the young solar-type star EK Draconis reveals the evidence for a stellar filament eruption associated with a superflare. This superflare emitted a radiated energy of $2.0\times10^{33}$ erg, and blue-shifted hydrogen absorption component with a large velocity of $-510$ km s$^{-1}$ was observed shortly after. The temporal changes in the spectra greatly resemble those of solar filament eruptions. Comparing this eruption with solar filament eruptions in terms of the length scale and velocity strongly suggests that a stellar CME occurred. The erupted filament mass of $1.1\times10^{18}$ g is 10 times larger than those of the largest solar CMEs. The massive filament eruption and an associated CME provide the opportunity to evaluate how they affect the environment of young exoplanets/young Earth and stellar mass/angular-momentum evolution.

At young ages, when radiation from the host star is high, and the planet is hot and inflated after formation, planetary atmospheric mass loss can be extremely strong compared to older planets. In turn, stellar winds are faster and denser for young stars compared to evolved main-sequence stars. Their interaction with escaping planetary atmospheres can substantially affect atmospheric mass loss rates, as well as the observable signatures of escaping atmospheres, with both effects expected to occur differently for young and evolved planets. We perform a comparative study of two systems around stars of similar masses but very different ages (50~Myr and 9~Gyr): TOI-942 and TOI-421. Both stars host two sub-Neptune-like planets at similar orbits and in similar mass ranges, which allows a direct comparison of the atmospheric escape and interactions with the stellar winds in the young and old systems. We perform the 3D atmospheric modeling of the four planets in TOI-942 and TOI-421 systems and make the theoretical predictions of possible observational signatures in Ly-alpha absorption. We find that accounting for the stellar wind interacting with planetary atmospheres is crucial for the interpretation of the observations for young planets. Additionally, we show that a particular energy distribution along the XUV spectra has a minor effect on the atmospheric mass-loss rates, but it is of crucial importance for modeling the Ly-alpha absorption and therefore for interpretation of observations.

Using path-integral Monte Carlo (PIMC) simulations, we have calculated energy of a crystal composed of atomic nuclei and uniform incompressible electron background in the temperature and density range, covering fully ionized layers of compact stellar objects, white dwarfs and neutron stars, including the high-density regime, where ion quantization is important. We have approximated the results by convenient analytic formulae, which allowed us to integrate and differentiate the energy with respect to temperature and density to obtain various thermodynamic functions such as Helmholtz free energy, specific heat, pressure, entropy etc. In particular, we have demonstrated, that the total crystal specific heat can exceed the well-known harmonic lattice contribution by a factor of 1.5 due to anharmonic effects. By combining our results with the PIMC thermodynamics of a quantum Coulomb liquid, updated in the present work, we were able to determine density dependences of such melting parameters as the Coulomb coupling strength at melting, latent heat, and a specific heat jump. Our results are necessary for realistic modelling of thermal evolution of compact degenerate stars.

The two planetary systems TOI-942 and TOI-421 share many similar characteristics, apart from their ages (50~Myr and 9~Gyr). Each of the stars hosts two sub-Neptune-like planets at similar orbits and in similar mass ranges. In this paper, we aim to investigate whether the similarity of the host stars and the configuration of the planetary systems can be taken as proof that the two systems were formed and evolved in a similar way. In paper I of this series, we performed a comparative study of these two systems using 3D modeling of atmospheric escape and its interaction with the stellar wind, for the four planets. We demonstrated that though the strong wind of the young star has a crucial effect on observable signatures, its effect on the atmospheric mass loss is minor in the evolutionary context. Here, we use atmosphere evolution models to track the evolution of planets in the younger system TOI-942 and also to constrain the past of the TOI-421 system. We demonstrate that despite all the similarities, the two planetary systems are on two very different evolutionary pathways. The inner planet in the younger system, TOI-942, will likely lose all of its atmosphere and become a super-Earth-like planet, while the outer planet will become a typical sub-Neptune. Concerning the older system, TOI-421, our evolution modeling suggests that they must have started their evolution with very substantial envelopes, which can be a hint of formation beyond the snow line.

Planet formation occurs around a wide range of stellar masses and stellar system architectures. An improved understanding of the formation process can be achieved by studying it across the full parameter space, particularly toward the extremes. Earlier studies of planets in close-in orbits around high-mass stars have revealed an increase in giant planet frequency with increasing stellar mass until a turnover point at 1.9 solar masses, above which the frequency rapidly decreases. This could potentially imply that planet formation is impeded around more massive stars, and that giant planets around stars exceeding 3 solar masses may be rare or non-existent. However, the methods used to detect planets in small orbits are insensitive to planets in wide orbits. Here we demonstrate the existence of a planet at 560 times the Sun-Earth distance from the 6-10 solar mass binary b Centauri through direct imaging. The planet-to-star mass ratio of 0.10-0.17% is similar to the Jupiter-Sun ratio, but the separation of the detected planet is ~100 times wider than that of Jupiter. Our results show that planets can reside in much more massive stellar systems than what would be expected from extrapolation of previous results. The planet is unlikely to have formed in-situ through the conventional core accretion mechanism, but might have formed elsewhere and arrived to its present location through dynamical interactions, or might have formed via gravitational instability.

Phosphorus (P) is a crucial element for life given its central role in several biomolecules. P-bearing molecules have been discovered in different regions of the Milky Way, but not yet towards an extragalactic environment. We have searched for P-bearing molecules towards the nearby starburst Galaxy NGC 253. Using observations from the ALMA Comprehensive High-resolution Extragalactic Molecular Inventory (ALCHEMI) project, we used the MADCUBA package to model the emission of P-bearing molecules assuming Local Thermodynamic Equilibrium (LTE) conditions. We have also performed a non-LTE analysis using SpectralRadex. We report the detection of a P-bearing molecule, phosphorus nitride (PN), for the first time in an extragalactic environment, towards two giant molecular clouds (GMCs) of NGC 253. The LTE analysis yields total PN beam-averaged column densities $N$=(1.20$\pm$0.09)$\times$10$^{13}$ cm$^{-2}$ and $N$=(6.5$\pm$1.6)$\times$10$^{12}$ cm$^{-2}$, which translate into abundances with respect to H$_2$ of $\chi$=(8.0$\pm$1.0)$\times$10$^{-12}$ and $\chi$=(4.4$\pm$1.2)$\times$10$^{-12}$. We derived a low excitation temperature of $T_{\rm ex}$=(4.4$\pm$1.3) K towards the GMC with the brightest PN emission, which indicates that PN is sub-thermally excited. The non-LTE analysis results in column densities consistent with the LTE values. We have also searched for other P-bearing molecules (PO, PH$_{3}$, CP and CCP), and upper limits were derived. The derived PO/PN ratios are $<$1.3 and $<$1.7. The abundance ratio between PN and the shock-tracer SiO derived towards NGC 253 follows the same trend previously found towards Galactic sources. Comparison of the observations with chemical models indicates that the derived molecular abundances of PN in NGC 253 can be explained by shock-driven chemistry followed by cosmic-ray-driven photochemistry.

To compare photometric properties of galaxies at different redshifts, we need to correct fluxes for the change of effective rest-frame wavelengths of filter bandpasses, called $k$-corrections. At redshifts $z>0.3$, the wavelength shift becomes so large that typical broadband photometric bands shift into the neighboring rest frame band. At $z=0.6-0.8$ the shift reaches two or even three bands. Therefore, we need perform $k$-corrections from one observed bandpass to another. Here we expand the methodology proposed by Chilingarian et al. (2010) and fit cross-band $k$-corrections by smooth low-order polynomial functions of one observed color and a redshift - this approach but without cross-band is implemented as standard functions in {\sc topcat}, which can be used for galaxies at $z<0.5$. We also computed analytic approximations for WISE bands, which were not available in the past. We now have a complete set of $k$-corrections coefficients, which allow us to process photometric measurements for galaxies out to redshift $z=1$. We calculated standard and cross-band $k$-corrections for about 4 million galaxies in second Reference Catalog of Spectral Energy Distributions (RCSEDv2) of galaxies and we showed that, in cases of widely used UV, optical and near-infrared filters, our analytic approximations work very well and can be used for extragalactic data from future wide-field surveys.

RCSEDv2 (https://rcsed2.voxastro.org/), the second Reference Catalog of Spectral Energy Distributions of galaxies, provides the largest homogeneously analyzed collection of optical galaxy spectra originating from several ground-based surveys collected between 1994 and 2019. The database contains astrophysical parameters obtained using the same data analysis approach from a sample of over 4 million optical spectra of galaxies and quasars: kinematics of stellar populations and ionized gas, chemical composition and age of stellar populations, gas phase metallicity. The dataset is available via Virtual Observatory access interfaces (IVOA TAP and SSAP) and through the web-site. Here we describe the RCSEDv2 spectroscopic dataset and the data processing and analysis.

The Reference Catalog of Spectral Energy Distributions of 800,000 galaxies (RCSED) includes the results of uniform re-processing of 800,000 SDSS DR7 galaxies at redshifts $0.007<z<0.6$ complemented with ultraviolet-to-infrared photometric data from GALEX, SDSS, and UKIDSS. The key difference between RCSED and existing databases of galaxy properties (NED, HyperLeda, part of SIMBAD) is that rather than providing a compilation of literature data, we perform homogeneous data analysis of spectral and photometric data using our own tools and publish derived physical properties of galaxies along with re-calibrated spectra and photometry and their best-fitting models. Here we present the 2nd release of our catalog, RCSEDv2 where we substantially expanded the spectral dataset to 4 million objects by including spectral data analysis for 10 large spectroscopic surveys (SDSS, SDSS/eBOSS, LAMOST, Hectospec, CfA redshift surveys, 2dFGRS, 6dFGS, DEEP2/3, WiggleZ). The photometric part has also been expanded by including DESI Legacy Survey, DES, UHS, ESO Public Surveys, and WISE in addition to GALEX, SDSS, and UKIDSS used in the original RCSED. This makes RCSEDv2 the largest database of galaxy properties and homogeneously processed spectral and photometric data up-to-date and creates a foundation for the analysis of future large-scale spectral surveys DESI and 4MOST.

We present a set of open-source web tools for visualization of spectral and imaging data, which we use in the second Reference Catalogue of Spectral Energy Distributions of galaxies RCSEDv2 (https://rcsed2.voxastro.org/). Using modern web frameworks Quasar and Vue.js we developed interactive viewers to visualize spectra and SEDs of galaxies and the diagrams presenting emission line ratios determined from the analysis of their spectra (BPT diagrams). The viewers are built in Javascript which puts a minimum load on the server side while providing full interactivity for the user. The use of modern web frameworks provides full customization making the viewers easily embeddable into web-sites of astronomical archives and databases. It also provides compatibility with popular third-party web-tools such as Aladin Lite.

RCSEDv2 (https://rcsed2.voxastro.org/), the second Reference Catalog of Spectral Energy Distributions of galaxies includes the largest homogeneously processed photometric dataset for 4 million galaxies assembled from several wide-field surveys. Here we describe the methodology of the photometric data homogenization. We first correct all photometric measurements for the foreground Galactic extinction, then convert them into the photometric system we adopted as a standard (GALEX + SDSS + UKIDSS + WISE). We computed aperture corrections into several pre-defined apertures by using published galaxy sizes / light profiles and image quality for each of the surveys. We accounted for k-corrections using our own analytic approximations. Such a homogeneous photometric catalog allows us to build fully calibrated SEDs for the galaxies in our sample (defined by the availability of their spectra) and enables direct scientific analysis of this unique extragalactic dataset.

The infrared astronomy group of Department of Astronomy and Astrophysics at Tata Institute of Fundamental Research has been pursuing astronomical instrumentation activities since its inception. The group has been routinely involved in balloon-borne astronomy programs from the field station at Hyderabad with indigenously developed payloads. Ground-based astronomical activities began with a single element infrared detector. Later, over time, larger format array detectors are being used in the cameras. These astronomy cameras have been routinely used at observatories across India. Recently, the group has also developed a laboratory model of the Infrared Spectroscopic Imaging Survey payload, targeted for the small satellite mission of the Indian Space Research Organisation, which will carry out spectroscopic measurements in the wavelength range 1.7 to 6.4 $\mu$m seamlessly

In Titan's nitrogen-methane atmosphere, photochemistry leads to the production of complex organic particles, forming Titan's thick haze layers. Laboratory-produced aerosol analogs, or "tholins", are produced in a number of laboratories; however, most previous studies have investigated analogs produced by only one laboratory rather than a systematic, comparative analysis. In this study, we performed a comparative study of an important material property, the surface energy, of seven tholin samples produced in three independent laboratories under a broad range of experimental conditions, and explored their commonalities and differences. All seven tholin samples are found to have high surface energies, and are therefore highly cohesive. Thus, if the surface sediments on Titan are similar to tholins, future missions such as Dragonfly will likely encounter sticky sediments. We also identified a commonality between all the tholin samples: a high dispersive (non-polar) surface energy component of at least 30 mJ/m2. This common property could be shared by the actual haze particles on Titan as well. Given that the most abundant species interacting with the haze on Titan (methane, ethane, and nitrogen) are non-polar in nature, the dispersive surface energy component of the haze particles could be a determinant factor in condensate-haze and haze-lake liquids interactions on Titan. With this common trait of tholin samples, we confirmed the findings of a previous study by Yu et al. (2020) that haze particles are likely good cloud condensation nuclei (CCN) for methane and ethane clouds and would likely be completely wetted by the hydrocarbon lakes on Titan.

We present the results of a time-coincident event search for low-energy electron antineutrinos in the KamLAND detector with gamma-ray bursts from the Gamma-ray Coordinates Network and Fermi Gamma-ray Burst Monitor. Using a variable coincidence time window of $\pm$500s plus the duration of each gamma-ray burst, no statistically significant excess above background is observed. We place the world's most stringent 90% confidence level upper limit on the electron antineutrino fluence below 17.5 MeV. Assuming a Fermi-Dirac neutrino energy spectrum from the gamma-ray burst source, we use the available redshift data to constrain the electron antineutrino luminosity and effective temperature.

Short-GRB progenitors could come in various flavors, depending on the nature of the merging compact stellar objects (including a stellar-mass black hole or not) or depending on their ages (millions or billions of years). At a redshift of z=0.122, the nearly face-on spiral host of the short GRB 080905A is one of the closest short-GRB host galaxies identified so far. This made it a preferred target to explore spatially resolved star-formation and to investigate the afterglow position in the context of its star formation structures. We used VLT/MUSE integral-field unit observations, supplemented by ATCA 5.5/9.0 GHz radio-continuum measurements and publicly available HST data, to study the star-formation activity in the GRB 080905A host galaxy. The MUSE observations reveal that the entire host is characterized by strong line emission. Using the Halpha line flux, we measure for the entire galaxy an SFR of about 1.6 Msun/yr, consistent with its non-detection by ATCA. Several individual star-forming regions are scattered across the host. The most luminous region has a Halpha luminosity that is nearly four times as high as the luminosity of the Tarantula nebula in the Large Magellanic Cloud. Even though star-forming activity can be traced as close to about 3 kpc (in projection) distance to the GRB explosion site, stellar population synthesis calculations show that none of the Halpha-bright star-forming regions is a likely birthplace of the short-GRB progenitor.

The gas-phase reaction of $\mathrm{O}+\mathrm{H}_3^+$ has two exothermic product channels, $\mathrm{OH}^+ +\mathrm{H}_2$ and $\mathrm{H}_2\mathrm{O}^+ +\mathrm{H}$. In the present study, we analyze experimental data from a merged-beams measurement to derive thermal rate coefficients resolved by product channel for the temperature range from 10 to 1000 K. Published astrochemical models either ignore the second product channel or apply a temperature-independent branching ratio of 70% vs. 30% for the formation of $\mathrm{OH}^+ +\mathrm{H}_2$ vs. $\mathrm{H}_2\mathrm{O}^+ +\mathrm{H}$, respectively, which originates from a single experimental data point measured at 295 K. Our results are consistent with this data point, but show a branching ratio that varies with temperature reaching 58% vs. 42% at 10 K. We provide recommended rate coefficients for the two product channels for two cases, one where the initial fine-structure population of the O$(^3P_J)$ reactant is in its $J=2$ ground state and the other one where it is in thermal equilibrium.

Numerical simulations have shown that massive dark matter haloes, which today host galaxy clusters, assemble their mass over time alternating periods of quiescent accretion and phases of rapid growth associated with major merger episodes. Observations of such events in clusters can provide insights on the astrophysical processes that characterise the properties of the intra-cluster medium, as well as the gravitational processes that contribute to their assembly. It is therefore of prime interest to devise a fast and reliable way of detecting such perturbed systems. We present a novel approach to identifying and timing major mergers in clusters characterised by large values of the halo sparsity. Using halo catalogues from the MultiDark-Planck2 simulation, we show that major merger events disrupt the radial mass distribution of haloes, thus leaving a distinct universal imprint on the evolution of halo sparsity over a period not exceeding two dynamical times. We exploit this feature using numerically calibrated distributions to test whether an observed galaxy cluster with given sparsity measurements has undergone a recent major merger and to eventually estimate when such an event occurred. We implement these statistical tools in a specifically developed public python library \textsc{lammas}, which we apply to the analysis of Abell 117, Abell 383 and Abell 2345 as test cases. Finding that, for example, Abell 117 had a major merger about 1.5 Gyr ago. This work opens the way to detecting and timing major mergers in galaxy clusters solely through measurements of their mass at different radii.

Sagittarius A* (Sgr A*), the Galactic Center supermassive black hole (SMBH), is one of the best targets to resolve the innermost region of SMBH with very long baseline interferometry (VLBI). In this study, we have carried out observations toward Sgr A* at 1.349 cm (22.223 GHz) and 6.950 mm (43.135 GHz) with the East Asian VLBI Network, as a part of the multi-wavelength campaign of the Event Horizon Telescope (EHT) in 2017 April. To mitigate scattering effects, the physically motivated scattering kernel model from Psaltis et al. (2018) and the scattering parameters from Johnson et al. (2018) have been applied. As a result, a single, symmetric Gaussian model well describes the intrinsic structure of Sgr A* at both wavelengths. From closure amplitudes, the major-axis sizes are ~704$\pm$102 $\mu$as (axial ratio $\sim$1.19$^{+0.24}_{-0.19}$) and $\sim$300$\pm$25 $\mu$as (axial ratio $\sim$1.28$\pm$0.2) at 1.349 cm and 6.95 mm respectively. Together with a quasi-simultaneous observation at 3.5 mm (86 GHz) by Issaoun et al. (2019), we show that the intrinsic size scales with observing wavelength as a power-law, with an index $\sim$1.2$\pm$0.2. Our results also provide estimates of the size and compact flux density at 1.3 mm, which can be incorporated into the analysis of the EHT observations. In terms of the origin of radio emission, we have compared the intrinsic structures with the accretion flow scenario, especially the radiatively inefficient accretion flow based on the Keplerian shell model. With this, we show that a nonthermal electron population is necessary to reproduce the source sizes.

The atmospheric chemical composition of a hot Jupiter can lead to insights into where in its natal protoplanetary disk it formed and its subsequent migration pathway. We use a 1-D chemical kinetics code to compute a suite of models across a range of elemental abundances to investigate the resultant abundances of key molecules in hot jupiter atmospheres. Our parameter sweep spans metallicities between 0.1x and 10x solar values for the C/H, O/H and N/H ratios, and equilibrium temperatures of 1000K and 2000K. We link this parameter sweep to the formation and migration models from previous works to predict connections between the atmospheric molecular abundances and formation pathways, for the molecules \ce{H2O}, \ce{CO}, \ce{CH4}, \ce{CO2}, \ce{HCN} and \ce{NH3}. We investigate atmospheric \ce{H2O} abundances in eight hot Jupiters reported in the literature. All eight planets fall within our predicted ranges for various formation models, however six of them are degenerate between multiple models and, hence, require additional molecular detections for constraining their formation histories. The other two planets, HD 189733~b and HD 209458~b, have water abundances that fall within ranges expected from planets that formed beyond the \ce{CO2} snowline. Finally, we investigate the detections of \ce{H2O}, \ce{CO}, \ce{CH4}, \ce{CO2}, \ce{HCN} and \ce{NH3} in the atmosphere of HD 209458~b and find that, within the framework of our model, the abundances of these molecules best match with a planet that formed between the \ce{CO2} and \ce{CO} snowlines and then underwent disk-free migration to reach its current location.

The gravitational harmonics measured from Juno and Cassini spacecrafts help us to specify the internal structure and chemical elements of Jupiter and Saturn, respectively. However, we still do not know much about the impact of rotation on the planetary internal structure as well as their formation. The centrifugal force induced by rotation deforms the planetary shape and partially counteracts the gravitational force. Thus, rotation will affect the critical core mass of the exoplanet. Once the atmospheric mass becomes comparable to the critical core mass, the planet will enter the runaway accretion phase and becomes a gas giant. We have confirmed that the critical core masses of rotating planets depend on the stiffness of the polytrope, the outer boundary conditions, and the thickness of the isothermal layer. The critical core mass with Bondi boundary condition is determined by the surface properties. The critical core mass of a rotating planet will increase with the core gravity (i.e., the innermost density). For the Hill boundary condition, the soft polytrope shares the same properties as planets with Bondi boundary condition. Since the total mass for planets with Hill boundary condition increases with the decrease of the polytropic index, higher core gravity is required for rotating planets. As a result, the critical core mass in the stiff Hill model sharply increases. The rotation effects become more important when the radiative and convective regions coexist. Besides, the critical core mass of planets with Hill (Bondi) boundary increases noticeably as the radiative layer becomes thinner (thicker).

Planet Planet scattering is a leading dynamical mechanism invoked to explain the present orbital distribution of exoplanets. Many stars belong to binary systems, therefore it is important to understand how this mechanism works in presence of a companion star. We focus on systems of three planets orbiting the primary star and estimate the timescale for instability finding that it scales with the keplerian period for systems that have the same ratio between inner planet and binary semimajor axes. An empirical formula is also derived from simulations to estimate how the the binary eccentricity affects the extent of the stability region. The presence of the secondary star affects the Planet Planet scattering outcomes causing a broadening of the final distribution in semimajor axis of the inner planet as some of the orbital energy of the planets is absorbed by the companion star. Repeated approaches to the secondary star causes also a significant reduction in the frequency of surviving two planet systems in particular for larger values of the inner planet semimajor axis. The formation of Kozai states with the companion star increases the number of planets which may be tidally circularized. To predict the possible final distribution of planets in binaries we have performed a large number of simulations where the initial semimajor axis of the inner planets is chosen randomly. For small values of the binary semimajor axis, the higher frequency of collision alter the final planet orbital distributions which, however, beyond 50 au appear to be scalable to wider binary separations.

Beam combiners are important components of an optical/infrared astrophysical interferometer, with many variants as to how to optimally combine two or more beams of light to fringe-track and obtain the complex fringe visibility. One such method is the use of an integrated optics chip that can instantaneously provide the measurement of the visibility without temporal or spatial modulation of the optical path. Current asymmetric planar designs are complex, resulting in a throughput penalty, and so here we present developments into a three dimensional triangular tricoupler that can provide the required interferometric information with a simple design and only three outputs. Such a beam combiner is planned to be integrated into the upcoming $\textit{Pyxis}$ interferometer, where it can serve as a high-throughput beam combiner with a low size footprint. Results into the characterisation of such a coupler are presented, highlighting a throughput of 89$\pm$11% and a flux splitting ratio between 33:33:33 and 52:31:17 over a 20% bandpass. We also show the response of the chip to changes in optical path, obtaining an instantaneous complex visibility and group delay estimate at each input delay.

NGC 2004 #115 is a recently identified black hole (BH) candidate in the Large Magellanic Cloud (LMC) containing a B star orbiting an unseen companion in a 2.9 day orbit and Be star tertiary. We show that the unseen companion is not a $25\,M_{\odot}$ BH, but a $(2-3)\,M_{\odot}$ luminous star. Analyzing the OGLE and MACHO light curves of the system, we detect ellipsoidal variability with amplitude 10 times larger than would be expected if the companion were a $25\,M_{\odot}$ BH, ruling out the low inclination required for a massive companion. The light curve also shows a clear reflection effect that is well-modeled with a $2.5\,M_{\odot}$ main-sequence secondary, ruling out a lower-mass BH or neutron star companion. We consider and reject models in which the system is a binary containing a stripped star orbiting the Be star: only a triple model with an outer Be star can explain both the observed light curve and radial velocities. Our results imply that the B star, whose slow projected rotation velocity and presumed tidal synchronization were interpreted as evidence for a low inclination (and thus a high companion mass), is far from being tidally synchronized: despite being in a 2.9 day orbit that is fully or nearly circularized ($e < 0.04$), its surface rotation period appears to be at least 20 days. We offer cautionary notes on the interpretation of dormant BH candidates in binaries.

We present an evaluation of a novel on-chip charge detector, called the Single electron Sensitive Read Out (SiSeRO), for charge-coupled device (CCD) image sensor applications. It uses a p-MOSFET transistor at the output stage with a depleted internal gate beneath the p-MOSFET. Charge transferred to the internal gate modulates the source-drain current of the transistor. We have developed a drain current readout module to characterize the detector. The prototype sensor achieves a charge/current conversion gain of 700 pA per electron, an equivalent noise charge (ENC) of 15 electrons (e-) root mean square (RMS), and a full width half maximum (FWHM) of 230 eV at 5.9 keV. In this paper, we discuss the SiSeRO working principle, the readout module developed at Stanford, and the first characterization test results of the SiSeRO prototypes. While at present only a proof-of-concept experiment, in the near future we plan to use next generation sensors with improved noise performance and an enhanced readout module. In particular, we are developing a readout module enabling Repetitive Non-Destructive Readout (RNDR) of the charge, which can in principle yield sub-electron ENC performance. With these developments, we eventually plan to build a matrix of SiSeRO amplifiers to develop an active pixel sensor with an on-chip ASIC-based readout system. Such a system, with fast readout speeds and sub-electron noise, could be effectively utilized in scientific applications requiring fast and low-noise spectro-imagers.

The cross-correlation between 21-cm intensity mapping experiments and photometric surveys of galaxies (or any other cosmological tracer with a broad radial kernel) is severely degraded by the loss of long-wavelength radial modes due to Galactic foreground contamination. Higher-order correlators are able to restore some of these modes due to the non-linear coupling between them and the local small-scale clustering induced by gravitational collapse. We explore the possibility of recovering information from the bispectrum between a photometric galaxy sample and an intensity mapping experiment, in the context of the clustering-redshifts technique. We demonstrate that the bispectrum is able to calibrate the redshift distribution of the photometric sample to the required accuracy of future experiments such as the Rubin Observatory, using future single-dish and interferometric 21-cm observations, in situations where the two-point function is not able to do so due to foreground contamination. We also show how this calibration is affected by the photometric redshift width $\sigma_{z,0}$ and maximum scale $k_{\mathrm{max}}$. We find that it is important to reach scales $k \gtrsim 0.3\,h\,\mathrm{Mpc}^{-1}$, with the constraints saturating at around $k\sim 1\,h\,\mathrm{Mpc}^{-1}$ for next-generation experiments.

Emission spectroscopy is a promising technique to observe atmospheres of rocky exoplanets, probing both their chemistry and thermal profiles. We present HyDRo, an atmospheric retrieval framework for thermal emission spectra of rocky exoplanets. HyDRo does not make prior assumptions about the background atmospheric composition, and can therefore be used to interpret spectra of secondary atmospheres with unknown compositions. We use HyDRo to assess the chemical constraints which can be placed on rocky exoplanet atmospheres using JWST. Firstly, we identify the best currently-known rocky exoplanet candidates for spectroscopic observations in thermal emission with JWST, finding >30 known rocky exoplanets whose thermal emission will be detectable by JWST/MIRI in fewer than 10 eclipses at R~10. We then consider the observations required to characterise the atmospheres of three promising rocky exoplanets across the ~400-800 K equilibrium temperature range: Trappist-1 b, GJ 1132 b, and LHS 3844 b. Considering a range of CO_2- to H_2O-rich atmospheric compositions, we find that as few as 8 eclipses of LHS 3844 b or GJ 1132 b with MIRI will be able to place important constraints on the chemical compositions of their atmospheres. This includes confident detections of CO_2 and H_2O in the case of a cloud-free CO_2-rich composition, besides ruling out a bare rock scenario. Similarly, 30 eclipses of Trappist-1 b with MIRI/LRS can allow detections of a cloud-free CO_2-rich or CO_2-H_2O atmosphere. HyDRo will allow important atmospheric constraints for rocky exoplanets using JWST observations, providing clues about their geochemical environments.

We are carrying out a dense monitoring of the blazar OJ 287 with Swift since late 2015 as part of our project MOMO (Multiwavelength Observations and Modeling of OJ 287). This is the densest existing monitoring of OJ 287 involving X-ray and UV data. In this latest publication of a sequence, we characterize the multiwavelength variability of OJ 287 based on >4000 Swift single-wave-band data sets including archival data since 2005. A structure function analysis reveals a characteristic timescale of ~5 days in the optical-UV at epochs of low-level activity, and larger during outbursts. The discrete correlation function shows zero lag between optical and UV, with tau = 0+-1 days at the epoch of densest cadence. During outbursts (in 2016/17 and 2020) the X-rays follow the UV with near-zero lags. However, during quiescence, the delay is 7-18 days with X-rays leading or lagging, interpreted as due to a different X-ray component dominated by inverse Compton emission. Scaling relations are used to derive the characteristic length scales of broad-line region and torus in OJ 287. A remarkable, symmetric UV--optical deep fade is identified in late 2017, lasting for 2 months. We rule out occultation from the passage of a dusty cloud and a model where the secondary black hole deflects the jet between the primary and observer. We speculate about a temporary dispersion or jet swing event in the core or in a bright quasi-stationary jet feature. The deep fade reveals an additional, spatially distinct X-ray component. The epoch 2020.9-2021.1 was searched for precursor flare activity predicted by the binary black hole model of OJ 287.

Terrestrial planets are commonly observed to orbit M dwarfs with close-in trajectories. In this work, we extensively perform N-body simulations of planetesimal accretion with three models of in-situ, inward migration and reversed migration to explore terrestrial formation in tightly compact systems of M dwarfs. In the simulations, the solid disks are assumed to be 0.01\% of the masses of host stars and spread from 0.01 to 0.5 AU with the surface density profile scaling with $r^{-k}$ according to the observations. Our results show that in-situ scenario may produce $7.77^{+3.23}_{-3.77}$ terrestrial planets with an average mass of $1.23^{+4.01}_{-0.93} \ M_{\oplus}$ around M dwarfs. The number of planets tends to increase as the disk slope is steeper or with a larger stellar mass. Moreover, we show that $2.55^{+1.45}_{-1.55}$ planets with mass of $3.76^{+8.77}_{-3.46} \ M_{\oplus}$ are formed in the systems via inward migration, while $2.85^{+1.15}_{-0.85}$ planets with $3.01^{+13.77}_{-2.71} \ M_{\oplus}$ are yielded under reversed migration. Migration scenarios can also deliver plentiful water from the exterior of ice line to the interior due to more efficient accretion. The simulation outcomes of reversed migration model produce the best matching with observations, being suggestive of a likely mechanism for planetary formation around M dwarfs.

Cosmological $\alpha$-attractors stand out as particularly compelling models to describe inflation in the very early universe, naturally meeting tight observational bounds from cosmic microwave background (CMB) experiments. We investigate $\alpha$-attractor potentials in the presence of an inflection point, leading to enhanced curvature perturbations on small scales. We study both single- and multi-field models, driven by scalar fields living on a hyperbolic field space. In the single-field case, ultra-slow-roll dynamics at the inflection point is responsible for the growth of the power spectrum, while in the multi-field set-up we study the effect of geometrical destabilisation and non-geodesic motion in field space. The two mechanisms can in principle be distinguished through the spectral shape of the resulting scalar power spectrum on small scales. These enhanced scalar perturbations can lead to primordial black hole (PBH) production and second-order gravitational wave (GW) generation. Due to the existence of universal predictions in $\alpha$-attractors, consistency with current CMB constraints on the large-scale spectral tilt implies that PBHs can only be produced with masses smaller than $10^8\,\text{g}$ and are accompanied by ultra-high frequency GWs, with a peak expected to be at frequencies of order $10\,\text{kHz}$ or above.

Realtime trigger and localization of bursts are the key functions of GECAM, which is an all-sky gamma-ray monitor launched in Dec 10, 2020. We developed a multifunctional trigger and localization software operating on the CPU of the GECAM electronic box (EBOX). This onboard software has the following features: high trigger efficiency for real celestial bursts with a suppression of false triggers caused by charged particle bursts and background fluctuation, dedicated localization algorithm optimized for short and long bursts respetively, short time latency of the trigger information which is downlinked throught the BeiDou satellite navigation System (BDS). This paper presents the detailed design and deveopment of this trigger and localization software system of GECAM, including the main functions, general design, workflow and algorithms, as well as the verification and demonstration of this software, including the on-ground trigger tests with simulated gamma-ray bursts made by a dedicated X-ray tube and the in-flight performance to real gamma-ray bursts and magnetar bursts.

The gravitational $N$-body problem, which is fundamentally important in astrophysics to predict the motion of $N$ celestial bodies under the mutual gravity of each other, is usually solved numerically because there is no known general analytical solution for $N>2$. Can an $N$-body problem be solved accurately by a neural network (NN)? Can a NN observe long-term conservation of energy and orbital angular momentum? Inspired by Wistom & Holman (1991)'s symplectic map, we present a neural $N$-body integrator for splitting the Hamiltonian into a two-body part, solvable analytically, and an interaction part that we approximate with a NN. Our neural symplectic $N$-body code integrates a general three-body system for $10^{5}$ steps without diverting from the ground truth dynamics obtained from a traditional $N$-body integrator. Moreover, it exhibits good inductive bias by successfully predicting the evolution of $N$-body systems that are no part of the training set.

We derive an approximate expression for the entropy of Hawking radiation filling a spherical box in stable thermodynamic equilibrium with the Schwarzschild black hole that produced the said radiation. The Bekenstein entropy bound is satisfied but the generalized second law might not be always guaranteed. We briefly discuss the possible origin of this unexpected result.

A new class of complex scalar field objects, which generalize the well known boson stars, was recently found as solutions to the Einstein-Klein-Gordon system. The generalization consists in incorporating some of the effects of angular momentum, while still maintaining the spacetime's spherical symmetry. These new solutions depend on an (integer) angular parameter $\ell$, and hence were named $\ell$-boson stars. Like the standard $\ell=0$ boson stars these configurations admit a stable branch in the solution space; however, contrary to them they have a morphology that presents a shell-like structure with a "hole" in the internal region. In this article we perform a thorough exploration of the parameter space, concentrating particularly on the extreme cases with large values of $\ell$. We show that the shells grow in size with the angular parameter, doing so linearly for large values, with the size growing faster than the thickness. Their mass also increases with $\ell$, but in such a way that their compactness, while also growing monotonically, converges to a finite value corresponding to about one half of the Buchdahl limit. Furthermore, we show that $\ell$-boson stars can be highly anisotropic, with the radial pressure diminishing relative to the tangential pressure for large $\ell$, reducing asymptotically to zero, and with the maximum density also approaching zero. We show that these properties can be understood by analyzing the asymptotic limit $\ell\rightarrow\infty$ of the field equations and their solutions. We also analyze the existence and characteristics of both timelike and null circular orbits, especially for very compact solutions.

Dark matter makes up 85% of the matter in the universe and 27% of its energy density, but we don't know what comprises dark matter. There are several compelling candidates for dark matter that have wavelike properties, including axions and dark photons. Wavelike dark matter can be detected using ultra-sensitive microwave cavities. The ADMX experiment uses a cylindrical cavity operating at the fundamental mode to search for axions in the few micro-eV mass range. However, the ADMX search technique becomes increasingly challenging with increasing axion mass. This is because higher masses require smaller-diameter cavities, and a smaller cavity volume reduces the signal strength. Thus, there is interest in developing more sophisticated resonators to overcome this problem. The ADMX-Orpheus experiment uses a dielectric-loaded Fabry-Perot cavity to search for axions and dark photons with masses approaching 100 micro-eV. Orpheus maintains a large volume by operating at a higher-order mode, and the dielectrics shape the electric field so that the mode couples more strongly to the axion and dark photon. This thesis describes the development and commissioning of ADMX-Orpheus to search for dark photons with masses between 65.5 micro-eV and 69.3 micro-eV.

We study a quintessence model for which the scalar field is disformally coupled to dark matter. The background mimics the LCDM cosmological evolution and the quintessence potential is not specified. A disformal effect due to the quintessential mass is seen in the growth rate of the cosmological structure on large scales. The disformal parameter renders no appreciable effect on the evolution of the total matter perturbation. An analysis of the conformal parameter and quintessential mass is investigated using the Redshift Space Distortion data to find the best-fit values that might explain the well-known sigma 8 tension. The best fit of the parameters indicates that the RSD data prefers the model to behave conformally.

The evidence for dark matter particles, $\chi$, is compelling based on Galactic to cosmological scale observations. Thus far, the promising weakly interacting massive particle scenario have eluded detection, motivating alternative models of dark matter. We consider scenarios involving superheavy dark matter (SHDM) that potentially can decay or annihilate to neutrinos and antineutrinos. In the mass range $m_\chi=10^7-10^{15}\,{\rm GeV}$, we evaluate the sensitivities of future observatories POEMMA and GRAND for indirect dark matter detection via the measurement of neutrino-induced extensive air showers (EAS), compute the Auger and ANITA limits using their last up-to-date sensitivities, and compare them with IceCube limits. We also show that the uncertainties related to the dark matter distribution in the Galactic halo have a large impact on the neutrino flux. We show that a ground-based radio detector such as GRAND can achieve high sensitivities due to its large effective area and high duty cycle. Space-based Cherenkov detectors such as POEMMA that measure the EAS optical Cherenkov signal have the advantage of full-sky coverage and rapid slewing, enabling an optimized SHDM observation strategy focusing on the Galactic Center. We show that increasing the field of view of the Cherenkov detectors can significantly enhance the sensitivity. Moreover, POEMMA's fluorescence observation mode that measures EAS above $20\,$EeV will achieve state-of-the-art sensitivity to SHDM properties at the highest mass scales.

In this paper, we review the history, current state-of-art, and physical applications of the spectral theory of two classes of random functions. One class consists of homogeneous and isotropic random fields defined on a Euclidean space and taking values in a real finite-dimensional linear space. In applications to continuum physics, such a field describes physical properties of a homogeneous and isotropic continuous medium in the situation, when a microstructure is attached to all medium points. The range of the field is the fixed point set of a symmetry class, where two compact Lie groups act by orthogonal representations. The material symmetry group of a homogeneous medium is the same at each point and acts trivially, while the group of physical symmetries may act nontrivially. In an isotropic random medium, the rank 1 (resp. rank 2) correlation tensors of the field transform under the action of the group of physical symmetries according to the above representation (resp. its tensor square), making the field isotropic. Another class consists of isotropic random cross-sections of homogeneous vector bundles over a coset space of a compact Lie group. In applications to cosmology, the coset space models the sky sphere, while the random cross-section models a cosmic background. The Cosmological Principle ensures that the cross-section is isotropic. For convenience of the reader, a necessary material from multilinear algebra, representation theory, and differential geometry is reviewed in Appendix.

Ultra-light primordial black holes with masses $M_{BH}<10^9$ g evaporate before big-bang nucleosynthesis producing all matter fields, including dark matter, in particular super-heavy dark matter: $M_{DM}\gtrsim 10^{10}$ GeV. If the dark matter gets its mass via $U(1)$ symmetry-breaking, the phase transition that gives a mass to the dark matter also produces cosmic strings which radiate gravitational waves. Because the symmetry-breaking scale $\Lambda_{CS}$ is of the same order as $M_{DM}$, the gravitational waves radiated by the cosmic strings have a large enough amplitude to be detectable across all frequencies accessible with current and planned experimental facilities. Moreover, an epoch of early primordial black hole domination introduces a unique spectral break in the gravitational wave spectrum whose frequency is related to the super-heavy dark matter mass. Hence, the features of a stochastic background of primordial gravitational waves could shed light on the primordial black hole origin of super-heavy dark matter. In this perspective, the recent finding of a stochastic common-spectrum process across many pulsars by two nano-frequency pulsar timing arrays would fix the dark matter mass to be $3\times 10^{13}~\text{GeV} \lesssim M_{DM} \lesssim 10^{14}~\text{GeV}$. The (non-)detection of a spectral break at $0.2~\text{Hz} \lesssim f_* \lesssim 0.4~\text{Hz}$ would (exclude) substantiate this interpretation of the signal.

A detailed analysis of (sub-)millimeter-wave spectra of the vibrational ground state ($\upsilon=0$) combined with the energetically lowest excited vibrational state ($\upsilon_{24}=1$; aldehyde torsion) of gauche-propanal (g-C$_2$H$_5$CHO) up to 500 GHz is presented. Both vibrational states, $\upsilon=0$ and $\upsilon_{24}=1$, are treated with tunneling rotation interactions between their two respective tunneling states, which originate from two stable degenerate gauche-conformers; left- and right-handed configurations separated by a small potential barrier. Thanks to double-modulation double-resonance (DM-DR) measurements, important but weak $c$-type transitions connecting the tunneling states could be unambiguously assigned. In addition, Coriolis interaction as well as Fermi resonance between the two vibrational states needed to be taken into account to derive fits with experimental accuracy using Pickett's SPFIT program in a reduced axis system (RAS). Based on the rotational analysis, the fundamental vibrational frequency $\nu_{24}$ of gauche-propanal is redetermined to 68.75037(30) cm$^{-1}$.

DarkSide-20k is a rare-event search experiment aimed at finding signals of dark matter particles. It is a dual-phase detector that registers ionisation and scintillation signals originating from the particles interacting with the liquid argon detector medium. It is enclosed in a single-phase liquid argon neutron veto tank, equipped with Gd-loaded panels for capturing neutrons. Since vetoing and particle identification are carried out using the light signal, it is crucial to maximise the light yield. Light collection efficiency depends on optical properties of the detector and particularly for the veto detector, which has a photosensor coverage of the order of a per cent, the reflectivity of the walls has a big impact. To quantify the amount of collected light, a comprehensive Geant4 simulation is performed, which uses optical characterisation data. In this work, a detailed description of the optics model for the veto of the experiment will be discussed.

The surface integral method for estimating ionic-covalent interactions in diatomic systems been successful in producing cross sections for mutual neutralisation (MN) in reasonable agreement with experimental results for branching fractions between final states in systems such as O$^+$/O$^-$ and N$^+$/O$^-$. However, for simpler cases of MN involving H$^-$ or D$^-$, such as Li$^+$/D$^-$ and Na$^+$/D$^-$, it has not produced results that are in agreement with experiments and other theoretical calculations; in particular, for Li$^+$/D$^-$ calculations predict the wrong ordering of importance of final channels, including the incorrect most populated channel. The reason for this anomaly is investigated and a leading constant to the asymptotic H$^-$ wavefunction is found that is different by roughly a factor $1/\sqrt{2}$ to that which has been used in previous calculations with the surface integral method involving H$^-$ or D$^-$. With this correction, far better agreement with both experimental results and with calculations with full quantum and LCAO methods is obtained. Further, it is shown that the surface integral method and LCAO methods have the same asymptotic behaviour, in contrast to previous claims. This result suggests the surface integral method, which is comparatively easy to calculate, has greater potential for estimating MN processes than earlier comparisons had suggested.

We distinguish between the notions of asymptotic causality and infrared causality for gravitational effective field theories, and show that the latter gives constraints consistent with gravitational positivity bounds. We re-explore the scattering of gravitational waves in a spherically symmetric background in the EFT of gravity in $D\ge 5$, for which the leading-order correction to Einstein gravity is determined by the Gauss-Bonnet operator. We reproduce the known result that the truncated effective theory exhibits apparent time advances relative to the background geometry for specific polarisations, which naively signal a violation of causality. We show that by properly identifying the regime of validity of the effective theory, the apparent time advance can be shown to be unresolvable. To illustrate this, we identify specific higher-dimension operators in the EFT expansion which become large for potentially resolvable time advances, rendering the EFT expansion invalid. Our results demonstrate how staying within the confines of the EFT, neither infrared nor asymptotic causality are ever violated for Einstein-Gauss-Bonnet gravity, no matter how low the scale, and furthermore its causality can be understood without appealing to a precise UV completion such as string theory.

In quantum information theory, quantum discord has been proposed as a tool to characterise the presence of "quantum correlations" between the subparts of a given system. Whether a system behaves quantum-mechanically or classically is believed to be impacted by the phenomenon of decoherence, which originates from the unavoidable interaction between this system and an environment. Generically, decoherence is associated with a decrease of the state purity, i.e. a transition from a pure to a mixed state. In this paper, we investigate how quantum discord is modified by this quantum-to-classical transition. This study is carried out on systems described by quadratic Hamiltonians and Gaussian states, with generalised squeezing parameters. A generic parametrisation is also introduced to describe the way the system is partitioned into two subsystems. We find that the evolution of quantum discord in presence of an environment is a competition between the growth of the squeezing amplitude and the decrease of the state purity. In phase space, this corresponds to whether the semi-minor axis of the Wigner ellipse increases or decreases, which has a clear geometrical interpretation. Finally, these considerations are applied to primordial cosmological perturbations, thus allowing us to investigate how large-scale structures in our universe, which are believed to arise from quantum fluctuations, can exhibit classical properties.

We consider the effective field theory of gravity around black holes, and show that the coefficients of the dimension-8 operators are tightly constrained by causality considerations. Those constraints are consistent with - but tighter than - previously derived causality and positivity bounds and imply that the effects of dimension-8 operators alone cannot be observable while remaining consistent with causality. We then establish in which regime one can expect the lower order operators to be potentially observable while preserving causality, providing a theoretical prior for future observations. We highlight the importance of `infrared causality' and show that the requirement of `asymptotic causality' or net (sub)luminality would fail to properly diagnose violations of causality.

Axions and axion-like particles (ALPs) are some of the most popular candidates for dark matter, with several viable production scenarios that make different predictions. In the scenario in which the axion is born after inflation, its field develops significant inhomogeneity and evolves in a highly nonlinear fashion. Understanding the eventual abundance and distribution of axionic dark matter in this scenario therefore requires dedicated numerical simulations. So far the community has focused its efforts on simulations of the QCD axion, a model that predicts a specific temperature dependence for the axion mass. Here, we go beyond the QCD axion, and perform a suite of simulations over a range of possible temperature dependencies labelled by a power-law index. We study the complex dynamics of the axion field, including the scaling of cosmic strings and domain walls, the spectrum of non-relativistic axions, the lifetime and internal structure of axitons, and the seeds of miniclusters. In particular, we quantify how much the string-wall network contributes to the dark matter abundance as a function of how quickly the axion mass grows. We find that a temperature-independent model produces 25\% more dark matter than the standard misalignment calculation. In contrast to this generic ALP, QCD axion models are almost six times less efficient at producing dark matter. Given the flourishing experimental campaign to search for ALPs, these results have potentially wide implications for direct and indirect searches.