Papers for Wednesday, Apr 07 2021

We present the first dedicated gamma-ray analysis of Jupiter, using 12 years of data from the Fermi Telescope. We find no robust evidence of gamma-ray emission, and set upper limits of $\sim10^{-9}~$GeV cm$^{-2} $s$^{-1}$ on the Jovian gamma-ray flux. We point out that Jupiter is an advantageous dark matter (DM) target due to its large surface area (compared to other solar system planets), and cool core temperature (compared to the Sun). These properties allow Jupiter to both capture and retain lighter DM, providing a complementary probe of sub-GeV DM. Our analysis focuses on the annihilation of sub-GeV DM to long-lived particles, which can escape the Jovian surface and decay into gamma rays. In this regime, we constrain DM-proton scattering cross-sections as low as $10^{-41}~$cm$^2$, which is up to ten orders of magnitude more sensitive than direct detection, and subject to fewer astrophysical uncertainties than other limits in this parameter space. Our work motivates follow-up studies with upcoming MeV telescopes such as AMEGO and e-ASTROGAM.

The dust production in debris discs by grinding collisions of planetesimals requires their orbits to be stirred. However, stirring levels remain largely unconstrained, and consequently the stirring mechanisms as well. This work shows how the sharpness of the outer edge of discs can be used to constrain the stirring levels. Namely, the sharper the edge is the lower the eccentricity dispersion must be. For a Rayleigh distribution of eccentricities ($e$), I find that the disc surface density near the outer edge can be parametrised as $\tanh[(r_{\max}-r)/l_{\rm out}]$, where $r_{\max}$ approximates the maximum semi-major axis and $l_{\rm out}$ defines the edge smoothness. If the semi-major axis distribution has sharp edges $e_\mathrm{rms}$ is roughly $1.2 l_{\rm out}/r_{\max}$, or $e_\mathrm{rms}=0.77 l_{\rm out}/r_{\max}$ if semi-major axes have diffused due to self-stirring. This model is fitted to ALMA data of five wide discs: HD 107146, HD 92945, HD 206893, AU Mic and HR 8799. The results show that HD 107146, HD 92945 and AU Mic have the sharpest outer edges, corresponding to $e_\mathrm{rms}$ values of $0.121\pm0.05$, $0.15^{+0.07}_{-0.05}$ and $0.10\pm0.02$ if their discs are self-stirred, suggesting the presence of Pluto-sized objects embedded in the disc. Although these stirring values are larger than typically assumed, the radial stirring of HD 92945 is in good agreement with its vertical stirring constrained by the disc height. HD 206893 and HR~8799, on the other hand, have smooth outer edges that are indicative of scattered discs since both systems have massive inner companions.

Recently, the LIGO-Virgo collaborations have reported the coalescence of a binary involving a black hole and a low-mass gap object (LMGO) with mass in the range $\sim2.5-5M_\odot$. Such detections, challenge our understanding of the black hole and neutron star mass spectrum, as well as how such binaries evolve especially if isolated. In this work we study the dynamical formation of compact object pairs, via multiple binary-single exchanges that occur at the cores of globular clusters. We start with a population of binary star systems, which interact with single compact objects as first generation black holes and LMGOs. We evaluate the rate of exchange interactions leading to the formation of compact object binaries. Our calculations include all possible types of binary-single exchange interactions and also the interactions of individual stars with compact object binaries that can evolve their orbital properties, leading to their eventual merger. We perform our calculations for the full range of the observed Milky Way globular cluster environments. We find that the exchanges are efficient in forming hard compact object binaries at the cores of dense astrophysical stellar environments. Furthermore, if the population size of the LMGOs is related to that of neutron stars, the inferred merger rate density of black hole-LMGO binaries inside globular clusters in the local Universe is estimated to be about $0.1 \, \text{Gpc}^{-3}\text{yr}^{-1}$.

Utilizing the Atacama Large Millimeter/submillimeter Array (ALMA), we present CS line maps in five rotational lines ($J_{\rm u}=7, 5, 4, 3, 2$) toward the circumnuclear disk (CND) and streamers of the Galactic Center. Our primary goal is to resolve the compact structures within the CND and the streamers, in order to understand the stability conditions of molecular cores in the vicinity of the supermassive black hole (SMBH) Sgr A*. Our data provide the first homogeneous high-resolution ($1.3'' = 0.05$ pc) observations aiming at resolving density and temperature structures. The CS clouds have sizes of $0.05-0.2$ pc with a broad range of velocity dispersion ($\sigma_{\rm FWHM}=5-40$ km s$^{-1}$). The CS clouds are a mixture of warm ($T_{\rm k}\ge 50-500$ K, n$_{\rm H_2}$=$10^{3-5}$ cm$^{-3}$) and cold gas ($T_{\rm k}\le 50$ K, n$_{\rm H_2}$=$10^{6-8}$ cm$^{-3}$). A stability analysis based on the unmagnetized virial theorem including tidal force shows that $84^{+16}_{-37}$ % of the total gas mass is tidally stable, which accounts for the majority of gas mass. Turbulence dominates the internal energy and thereby sets the threshold densities $10-100$ times higher than the tidal limit at distance $\ge 1.5$ pc to Sgr A*, and therefore, inhibits the clouds from collapsing to form stars near the SMBH. However, within the central $1.5$ pc, the tidal force overrides turbulence and the threshold densities for a gravitational collapse quickly grow to $\ge 10^{8}$ cm$^{-3}$.

Application of the radial velocity (RV) technique in the near infrared is valuable because of the diminished impact of stellar activity at longer wavelengths, making it particularly advantageous for the study of late-type stars but also for solar-type objects. In this paper, we present the IGRINS RV open source python pipeline for computing infrared RV measurements from reduced spectra taken with IGRINS, a R ~ 45,000 spectrograph with simultaneous coverage of the H band (1.49--1.80 $\mu$m) and K band (1.96--2.46 $\mu$m). Using a modified forward modeling technique, we construct high resolution telluric templates from A0 standard observations on a nightly basis to provide a source of common-path wavelength calibration while mitigating the need to mask or correct for telluric absorption. Telluric standard observations are also used to model the variations in instrumental resolution across the detector, including a yearlong period when the K band was defocused. Without any additional instrument hardware, such as a gas cell or laser frequency comb, we are able to achieve precisions of 26.8 $\rm m\,s^{-1}$ in the K band and 31.1 $\rm m\,s^{-1}$ in the H band for narrow-line hosts. These precisions are empirically determined by a monitoring campaign of two RV standard stars as well as the successful retrieval of planet-induced RV signals for both HD 189733 and $\tau$ Boo A; furthermore, our results affirm the presence of the Rossiter-McLaughlin effect for HD 189733. The IGRINS RV pipeline extends another important science capability to IGRINS, with publicly available software designed for widespread use.

We propose a novel source of gravitational wave emission: the inspirals of compact fragments inside primordial supermassive stars (SMSs). Such systems are thought to be an essential channel in the as-yet little understood formation of supermassive black holes (SMBHs). One model suggests that high accretion rates of $0.1$-1 M$_\odot$/yr attainable in atomically-cooled primordial halos can lead to the formation of a nuclear-burning SMS. This will ultimately undergo collapse through a relativistic instability, leaving a massive BH remnant. Recent simulations suggest that supermassive stars rarely form in isolation, and that companion stars and even black holes formed may be captured/accreted and inspiral to the SMS core due to gas dynamical friction. Here, we explore the GW emission produced from such inspirals, which could probe the formation and evolution of SMS and seeds of the first supermassive black holes. We use a semi-analytic gas-dynamical friction model of the inspirals in the SMS to characterize their properties. We find such sources could potentially be observable by upcoming space-born GW-detectors at their formation redshifts with the benefit of gravitational lensing. Mergers within closely-related quasi-stars may produce a much stronger signal, though disambiguating such events from other high-z events may prove challenging.

Using ultraviolet (UV) light curves we constrain the circumstellar environments of 1080 Type Ia supernovae (SNe Ia) within $z<0.5$ from archival Galaxy Evolution Explorer (GALEX) observations. All SNe Ia are required to have pre- and post-explosion GALEX observations to ensure adequate subtraction of the host-galaxy flux. Using the late-time GALEX observations we look for the UV excess expected from any interaction between the SN ejecta and circumstellar material (CSM). Four SNe Ia are detected near maximum light and we compare the GALEX photometry to archival data, but we find none of our targets show convincing evidence of CSM interaction. A recent Hubble Space Telescope (HST) survey estimates that $\sim6\%$ of SNe Ia may interact with distant CSM, but statistical inferences are complicated by the small sample size and selection effects. By injecting model light curves into our data and then recovering them, we constrain a broad range of CSM interactions based on the CSM interaction start time and the maximum luminosity. Combining our GALEX non-detections with the HST results, we constrain occurrence of late-onset CSM interaction among SNe Ia with moderate CSM interaction, similar to that observed in PTF11kx, to $f_\text{CSM}\lesssim7.3\%$ between $0-500$ days after discovery and $\lesssim3.1\%$ between $500-1000$ days after discovery at $90\%$ confidence. For weaker CSM interactions similar to SN 2015cp, we obtain limits of $\lesssim14\%$ and $\lesssim4.9\%$, respectively, for the same time ranges.

The exoplanetary system of HR 8799 is one of the rare systems in which multiple planets have been directly imaged. Its architecture is strikingly similar to that of the Solar System, with the four imaged giant planets surrounding a warm dust belt analogous to the Asteroid Belt, and themselves being surrounded by a cold dust belt analogue to the Kuiper Belt. Previous observations of this cold belt with ALMA in Band 6 (1.3 mm) revealed its inner edge, but analyses of the data differ on its precise location. It was therefore unclear whether the outermost planet HR 8799 b was dynamically sculpting it or not. We present here new ALMA observations of this debris disk in Band 7 (340 GHz, 880 micron). These are the most detailed observations of this disk obtained so far, with a resolution of 1" (40 au) and sensitivity of $9.8\,\mu\mathrm{Jy\,beam^{-1}}$, which allowed us to recover the disk structure with high confidence. In order to constrain the disk morphology, we fit its emission using radiative transfer models combined with a MCMC procedure. We find that this disk cannot be adequately represented by a single power law with sharp edges. It exhibits a smoothly rising inner edge and smoothly falling outer edge, with a peak in between, as expected from a disk that contains a high eccentricity component, hence confirming previous findings. Whether this excited population and inner edge shape stem from the presence of an additional planet remains, however, an open question.

Galaxies inhabit a wide range of environments and therefore are affected by different physical mechanisms. Spatially resolved maps combined with the knowledge of the hosting environment are very powerful to classify galaxies by physical process. In the context of the GAs Stripping Phenomena in galaxies (GASP), we present a study of 27 non-cluster galaxies: 24 of them were selected for showing asymmetries and disturbances in the optical morphology, suggestive of gas stripping, three of them are passive galaxies and were included to characterize the final stages of galaxy evolution. We therefore provide a panorama of the different processes taking place in low-density environments. The analysis of VLT/MUSE data allows us to separate galaxies into the following categories: Galaxy-galaxy interactions (2 galaxies), mergers (6), ram pressure stripping (4), cosmic web stripping (2), cosmic web enhancement (5), gas accretion (3), starvation (3). In one galaxy we identify the combination of merger and ram pressure stripping. Only 6/27 of these galaxies have just a tentative classification. We then investigate where these galaxies are located on scaling relations determined for a sample of undisturbed galaxies. Our analysis shows the successes and limitations of a visual optical selection in identifying the processes that deplete galaxies of their gas content and probes the power of IFU data in pinning down the acting mechanism.

The formation and evolution of galaxies is known to be sensitive to tidal processes leading to intrinsic correlations between their shapes and orientations. Such correlations can be measured to high significance today, suggesting that cosmological information can be extracted from them. Among the most pressing questions in particle physics and cosmology is the nature of dark matter. If dark matter is self-interacting, it can leave an imprint on galaxy shapes. In this work, we investigate whether self-interactions can produce a long-lasting imprint on intrinsic galaxy shape correlations. We investigate this observable at low redshift ($z<0.4$) using a state-of-the-art suite of cosmological hydro-dynamical simulations where the dark matter model is varied. We find that dark matter self-interactions induce a mass dependent suppression in the intrinsic alignment signal by up to 50\% out to ten's of mega-parsecs, showing that self-interactions can impact structure outside the very core of clusters. We find evidence that self-interactions have a scale-dependent impact on the intrinsic alignment signal that is sufficiently different from signatures introduced by differing baryonic physics prescriptions, suggesting that it is detectable with up-coming all-sky surveys.

In order to connect galaxy clusters to their progenitor protoclusters, we must constrain the star formation histories within their member galaxies and the timescale of virial collapse. In this paper we characterize the complex star-forming properties of a $z=2.5$ protocluster in the COSMOS field using ALMA dust continuum and new VLA CO(1-0) observations of two filaments associated with the structure, sometimes referred to as the "Hyperion" protocluster. We focus in particular on the protocluster "core" which has previously been suggested as the highest redshift bona fide galaxy cluster traced by extended X-ray emission in a stacked Chandra/XMM image. We re-analyze this data and refute these claims, finding that at least 40 $\pm$ 17% of extended X-ray sources of similar luminosity and size at this redshift arise instead from Inverse Compton scattering off recently extinguished radio galaxies rather than intracluster medium. Using ancillary COSMOS data, we also constrain the SEDs of the two filaments' eight constituent galaxies from the rest-frame UV to radio. We do not find evidence for enhanced star formation efficiency in the core and conclude that the constituent galaxies are already massive (M$_{\star} \approx 10^{11} M_{\odot}$), with molecular gas reservoirs $>10^{10} M_{\odot}$ that will be depleted within 200-400 Myr. Finally, we calculate the halo mass of the nested core at $z=2.5$ and conclude that it will collapse into a cluster of 2-9 $\times 10^{14} M_{\odot}$, comparable to the size of the Coma cluster at $z=0$ and accounting for at least 50% of the total estimated halo mass of the extended "Hyperion" structure.

We report the analysis of planetary microlensing event OGLE-2018-BLG-1185, which was observed by a large number of ground-based telescopes and by the $Spitzer$ Space Telescope. The ground-based light curve indicates a low planet-host star mass ratio of $q = (6.9 \pm 0.2) \times 10^{-5}$, which is near the peak of the wide-orbit exoplanet mass-ratio distribution. We estimate the host star and planet masses with a Bayesian analysis using the measured angular Einstein radius under the assumption that stars of all masses have an equal probability to host this planet. The flux variation observed by $Spitzer$ was marginal, but still places a constraint on the microlens parallax. Imposing a conservative constraint that this flux variation should be $\Delta f_{\rm Spz} < 4$ instrumental flux units indicates a host mass of $M_{\rm host} = 0.37^{+0.35}_{-0.21}\ M_\odot$ and a planet mass of $m_{\rm p} = 8.4^{+7.9}_{-4.7}\ M_\oplus$. A Bayesian analysis including the full parallax constraint from $Spitzer$ suggests smaller host star and planet masses of $M_{\rm host} = 0.091^{+0.064}_{-0.018}\ M_\odot$ and $m_{\rm p} = 2.1^{+1.5}_{-0.4}\ M_\oplus$, respectively. Future high-resolution imaging observations with $HST$ or ELTs could distinguish between these two scenarios and help to reveal the planetary system properties in more detail.

We describe a simple model which explains the qualitative and (approximate) quantitative features of the distribution of orbital velocities of merging pairs of dark matter halos. Our model considers a primary dark matter halo as a perturber in a background of secondary halos with velocities described by linear theory. By evaluating the ensemble of secondary halos on orbits within the perturbing halo's "loss cone" we derive the distribution of orbital parameters of these captured halos. This model is able provide qualitative explanations for the features of this distribution as measured from N-body simulations, and is in approximate quantitative agreement with those measurements. As the velocity dispersion of the background halos is larger on smaller scales our model predicts an overall increase in the characteristic velocities of merging halos, relative to the virial velocities of those halos, in lower mass systems. Our model also provides a simple explanation for the measured independence of the orbital velocity distribution function on redshift when considered at fixed peak height. By connecting the orbital parameter distribution to the underlying power spectrum our model also allows for estimates to be made of the effect of modifying that power spectrum, for example by including a truncation at large wavenumber. For plausible warm dark matter models we find that this truncation has only a small effect on the predicted distributions.

We present a new catalog of $9318$ Ly$\alpha$ emitter (LAE) candidates at $z = 2.2$, $3.3$, $4.9$, $5.7$, $6.6$, and $7.0$ that are photometrically selected by the SILVERRUSH program with a machine learning technique from large area (up to $25.0$ deg$^2$) imaging data with six narrowband filters taken by the Subaru Strategic Program with Hyper Suprime-Cam (HSC SSP) and a Subaru intensive program, Cosmic HydrOgen Reionization Unveiled with Subaru (CHORUS). We construct a convolutional neural network that distinguishes between real LAEs and contaminants with a completeness of $94$% and a contamination rate of $1$%, enabling us to efficiently remove contaminants from the photometrically selected LAE candidates. We confirm that our LAE catalogs include $177$ LAEs that have been spectroscopically identified in our SILVERRUSH programs and previous studies, ensuring the validity of our machine learning selection. In addition, we find that the object-matching rates between our LAE catalogs and our previous results are $\simeq 80$-$100$% at bright NB magnitudes of $\lesssim 24$ mag. We also confirm that the surface number densities of our LAE candidates are consistent with previous results. Our LAE catalogs will be made public on our project webpage.

Symplectic integrators are widely used for the study of planetary dynamics and other $N$-body problems. In a study of the outer Solar system, we demonstrate that individual symplectic integrations can yield biased errors in the semi-major axes and possibly other orbital elements. The bias is resolved by studying an ensemble of initial conditions of the outer Solar system. Such statistical sampling could significantly improve measurement of planetary system properties like their secular frequencies. We also compared the distributions of action-like variables between high and low accuracy integrations; traditional statistical metrics are unable to distinguish the distribution functions.

One of the key open questions in extragalactic astronomy is what stops star formation in galaxies. While it is clear that the cold gas reservoir, which fuels the formation of new stars, must be affected first, how this happens and what are the dominant physical mechanisms involved is still a matter of debate. At least for satellite galaxies, it is generally accepted that internal processes alone cannot be responsible for fully quenching their star formation, but that environment should play an important, if not dominant, role. In nearby clusters, we see examples of cold gas being removed from the star-forming disks of galaxies moving through the intracluster medium, but whether active stripping is widespread and/or necessary to halt star formation in satellites, or quenching is just a consequence of the inability of these galaxies to replenish their cold gas reservoirs, remains unclear. In this work, we review the current status of environmental studies of cold gas in star-forming satellites in the local Universe from an observational perspective, focusing on the evidence for a physical link between cold gas stripping and quenching of the star formation. We find that stripping of cold gas is ubiquitous in satellite galaxies in both group and cluster environments. While hydrodynamical mechanisms such as ram pressure are important, the emerging picture across the full range of dark matter halos and stellar masses is a complex one, where different physical mechanisms may act simultaneously and cannot always be easily separated. Most importantly, we show that stripping does not always lead to full quenching, as only a fraction of the cold gas reservoir might be affected at the first pericentre passage. We argue that this is a key point to reconcile apparent tensions between statistical and detailed analyses of satellite galaxies...(abridged)

We present a catalog of 167 newly discovered, irregular variables spanning a $\sim$7 deg${^2}$ area that encompasses the G 305 star-forming complex, one of the most luminous giant H II regions in the Galaxy. We aim to unveil and characterize the young stellar object (YSO) population of the region by analyzing the $K_{\rm s}$-band variability and $JHK_{\rm s}$ infrared colors from the {\it VISTA Variables in the V\'ia L\'actea} (VVV) survey. Additionally, SDSS-IV APOGEE-2 infrared spectra of selected objects are analyzed. The sample show relatively high amplitudes ($0.661<\Delta K_{\rm S} <3.521$ mag). Most of them resemble sources with outbursts with amplitude $>1$ mag and duration longer than a few days, typically at least a year, known as {\it Eruptive Variables}. About 60% are likely to be Class II/Flat/I objects. This is also confirmed by the spectral index $\alpha$ when available. From the analysis of APOGEE-2 near-infrared spectra of sources in the region, another 122 stars are classified as YSOs, and displays some infrared variability. The measured effective temperature $T_{\rm eff}$ peak is around 4000K and they are slightly super-solar in metal abundance. The modal radial velocity is approximately $-$41 km/s. Combining available catalogs of YSOs in the region with our data, we investigate the spatial distributions of 700 YSOs. They are clearly concentrated within the central cavity formed by the massive clusters Danks 1 and 2. The calculated surface density for the entire catalog is 0.025 YSOs/pc$^{-2}$, while the central cavity contains 10 times more objects per area (0.238 YSOs/pc$^{-2}$).

We present new Atacama Large Millimeter/submillimeter Array Band 7 observational results of a Lyman break galaxy at $ z=7.15 $, B14-65666 ("Big Three Dragons"), which is an object detected in [OIII] 88 $\rm{\mu m}$, [CII] 158 $\rm{\mu m}$, and dust-continuum emission during the epoch of reionization. Our targets are the [NII] 122 $\rm{\mu m}$ fine-structure emission line and underlying 120 $\rm{\mu m}$ dust continuum. The dust continuum is detected with a $ \sim $19$ \sigma $ significance. From far-infrared spectral energy distribution sampled at 90, 120, and 160 $\rm{\mu m}$, we obtaine a best-fit dust temperature of $ 40 $ K ($ 79 $ K) and an infrared luminosity of $ \log_{10}(L_{\rm IR}/{\rm L}_\odot)=11.6$ ($12.1$) at the emissivity index $ \beta = 2.0 $ (1.0). The [NII] 122 $\rm{\mu m}$ line is not detected. The 3$ \sigma $ upper limit of the [NII] luminosity is $ 8.1 \times 10^7\ {\rm L}_\odot$. From the [NII], [OIII], and [CII] line luminosities, we use the Cloudy photoionization code to estimate nebular parameters as functions of metallicity. If the metallicity of the galaxy is high ($ Z > 0.4\ {\rm Z}_\odot$), the ionization parameter and hydrogen density are $ \log_{10} U \simeq -2.7\pm0.1$ and $ n_\text{H} \simeq 50$-$250\ {\rm cm}^{-3}$, respectively, which are comparable to those measured in low-redshift galaxies. The nitrogen-to-oxygen abundance ratio, $\rm{N/O}$, is constrained to be sub-solar. At $ Z < 0.4\ {\rm Z}_\odot$, the allowed $ U $ drastically increases as the assumed metallicity decreases. For high ionization parameters, the $\rm{N/O}$ constraint becomes weak. Finally, our Cloudy models predict the location of B14-65666 on the BPT diagram, thereby allowing a comparison with low-redshift galaxies.

The extreme timing stability of radio millisecond pulsars (MSPs) combined with their exotic environment and evolutionary history makes them excellent laboratories to probe matter in extreme condition. Population studies indicate that we have discovered less than five per cent of the MSPs of our Galaxy, implying that a huge majority of radio MSPs are waiting to be discovered with improved search techniques and more sensitive surveys. In this chapter, we provide an overview of the present status of ongoing and upcoming surveys for MSPs. Observed spectra, profile and polarisation properties of known radio MSPs are also summarised. Finally, we describe how the timing studies of radio MSPs enable a huge science return including attempts to detect gravitational waves using an array of MSPs, gravity tests using individual interesting MSP systems, as well as probing the intra-binary material using eclipses observed in MSPs in compact binary systems.

The radiatively driven wind of the primary star in wind-fed X-ray binaries can be suppressed by the X-ray irradiation of the compact secondary star. This causes feedback between the wind and the X-ray luminosity of the compact star. We estimated how the wind velocity on the face-on side of the donor star depends on the spectral state of the high-mass X-ray binary Cygnus X-3. We modeled the supersonic part of the wind by computing the line force (force multiplier) with the Castor, Abbott and Klein formalism and XSTAR physics and by solving the mass conservation and momentum balance equations. We computed the line force locally in the wind considering the radiation fields from both the donor and the compact star in each spectral state. The wind equations were solved at different orbital angles from the line joining the stars and taking the effect of wind clumping into account. Wind-induced accretion luminosities were estimated using the Bondi-Hoyle-Lyttleton formalism and computed wind velocities at the compact star. We found a correlation between the luminosities estimated from the observations for each spectral state of Cyg X-3 and the computed accretion luminosities assuming moderate wind clumping and a low mass of the compact star. For high wind clumping this correlation disappears. We show that soft X-rays (EUV) from the compact star penetrate the wind from the donor star and diminish the line force and consequently the wind velocity on the face-on side. This increases the computed accretion luminosities qualitatively in a similar manner as observed in the spectral evolution of Cyg X-3 for a moderate clumping volume filling factor and a compact star mass of a few (2 - 3) solar masses.

We present the first systematic study of clouds observed during twilight on Mars. We analyze images obtained by the Visual Monitoring Camera (VMC) on Mars Express between 2007 and 2020. Using an automated retrieval algorithm we found 407 cases of clouds observed at twilight, in which the geometry of the observations allows to derive the minimum altitude, revealing that many of these clouds are in the mesosphere (above 40km and up to 90km). The majority of these mesospheric clouds were detected in mid-latitudes at local autumn and winter, a new trend only hinted at by previous studies. In particular, we find a massive concentration of clouds in the southern mid-latitudes between Terra Cimmeria and Aonia, a region where high altitude events have been previously observed. We propose that there is an unknown mechanism in these regions that enhances the probability to host high altitude clouds around the southern winter solstice.

The temperatures of the plasma in the supernova remnants (SNRs) are initially very low just after the shock heating. The electron temperature (kT_{e}) increases quickly by Coulomb interaction, and then the energetic electrons gradually ionize atoms to increase the ionization temperature (kT_{i}). The observational fact is that most of the young and middle-to-old aged SNRs have lower kT_{i} than kT_{e} after the shock heating. The temperature evolution in the shell-like SNRs has been explained by this ionizing plasma (IP) scenario. On the other hand, in the last decade, a significant fraction of the mixed morphology SNRs was found to exhibit a recombining plasma (RP) with higher kT_{i} than kT_{e}. The origin and the evolution mechanism of the RP SNRs have been puzzling. To address this puzzle, this paper presents the kT_{e} and kT_{i} profiles using the observed results by follow-up Suzaku observations, and then proposes a new scenario for the temperature and morphology evolutions in the IP and RP SNRs.

Context: The formation of high-mass star-forming regions from their parental gas cloud and the subsequent fragmentation processes lie at the heart of star formation research. Aims: We aim to study the dynamical and fragmentation properties at very early evolutionary stages of high-mass star formation. Methods: Employing the NOrthern Extended Millimeter Array (NOEMA) and the IRAM 30m telescope, we observed two young high-mass star-forming regions, ISOSS22478 and ISOSS23053, in the 1.3mm continuum and spectral line emission at a high angular resolution (~0.8''). Results: We resolved 29 cores that are mostly located along filament-like structures. Depending on the temperature assumption, these cores follow a mass-size relation of approximately M~r^2.0, corresponding to constant mean column densities. However, with different temperature assumptions, a steeper mass-size relation up to M~r^3.0, which would be more likely to correspond to constant mean volume densities, cannot be ruled out. The correlation of the core masses with their nearest neighbor separations is consistent with thermal Jeans fragmentation. We found hardly any core separations at the spatial resolution limit, indicating that the data resolve the large-scale fragmentation well. Although the kinematics of the two regions appear very different at first sight - multiple velocity components along filaments in ISOSS22478 versus a steep velocity gradient of more than 50km/s/pc in ISOSS23053 - the findings can be explained within the framework of a dynamical cloud collapse scenario. Conclusions: While our data are consistent with a dynamical cloud collapse scenario and subsequent thermal Jeans fragmentation, the importance of additional environmental properties, such as the magnetization of the gas or external shocks triggering converging gas flows, is nonetheless not as well constrained and would require future investigation.

The circular restricted three body problem, which considers the dynamics of an infinitesimal particle in the presence of the gravitational interaction with two massive bodies moving on circular orbits about their common center of mass, is a very useful model for investigating the behavior of real astronomical objects in the Solar System. In such a system, there are five Lagrangian equilibrium points, and one important characteristic of the motion is the existence of linearly stable equilibria at the two equilibrium points that form equilateral triangles with the primaries, in the plane of the primaries' orbit. We analyze the stability of motion in the restricted three body problem by using the concept of Jacobi stability, as introduced and developed in the Kosambi-Cartan-Chern (KCC) theory. The KCC theory is a differential geometric approach to the variational equations describing the deviation of the whole trajectory of a dynamical system with respect to the nearby ones. We obtain the general result that, from the point of view of the KCC theory and of Jacobi stability, all five Lagrangian equilibrium points of the restricted three body problem are unstable.

The paper presents magnetic field measurements for 15 chemically peculiar (CP) stars of subgroup~1b in the OrionOB1 association. We have found that the proportion of stars with strong magnetic fields among these 15 CP stars is almost twice as large as in subgroup 1a. Along with this, the age of subgroup 1b is estimated as 2 Myr, and the age of subgroup~1a is in the order of 10 Myr. The average root-mean-square magnetic field Be for stars in subgroup 1b is 2.3 times higher than that for stars in subgroup 1a. The conclusions obtained fall within the concept of the fossil origin of large-scale magnetic fields in B and A stars, but the rate of field weakening with age appears anomalously high. We present our results as an important observational test for calibrating the theory of stellar magnetic field formation and evolution.

The OSIRIS-REx spacecraft encountered the asteroid (101955) Bennu on December 3, 2018, and has since acquired extensive data from the payload of scientific instruments on board. In 2019, the OSIRIS-REx team selected primary and backup sample collection sites, called Nightingale and Osprey, respectively. On October 20, 2020, OSIRIS-REx successfully collected material from Nightingale. In this work, we apply an unsupervised machine learning classification through the K-Means algorithm to spectrophotometrically characterize the surface of Bennu, and in particular Nightingale and Osprey. We first analyze a global mosaic of Bennu, from which we find four clusters scattered across the surface, reduced to three when we normalize the images at 550 nm. The three spectral clusters are associated with boulders and show significant differences in spectral slope and UV value. We do not see evidence of latitudinal non-uniformity, which suggests that Bennu's surface is well-mixed. In our higher-resolution analysis of the primary and backup sample sites, we find three representative normalized clusters, confirming an inverse correlation between reflectance and spectral slope (the darkest areas being the reddest ones) and between b' normalized reflectance and slope. Nightingale and Osprey are redder than the global surface of Bennu by more than $1\sigma$ from average, consistent with previous findings, with Nightingale being the reddest ($S' = (- 0.3 \pm 1.0) \times 10^{- 3}$ percent per thousand angstroms). We see hints of a weak absorption band at 550 nm at the candidate sample sites and globally, which lends support to the proposed presence of magnetite on Bennu.

This paper reviews the question of whether the wide separation double quasar Q2138-431 is a gravitational lens. From early work, the two quasar images are known to have almost identical spectra and redshifts, but no lensing galaxy has so far been detected. In this paper we used recent deep surveys in infrared and optical bands to search for the presence of a galaxy with the expected properties of a gravitational lens. The search revealed a $5 \sigma$ detection of a faint galaxy between the two quasar images on a deep $J$-band frame from the VISTA Science Archive, with apparent magnitude $J = 20.68$. Non-detection in the $I$-band implied a redshift $z > 0.6$, and mass modelling of the quasar system gave a mass of $1.31 \times 10^{12} M_\odot$ for the lensing galaxy, with mass-to-light ratio $M_{\odot}/L_{\odot} = 9.0$. Archival photographic data from the UK 1.2m Schmidt telescope covering 25 years were used to construct light curves for the two quasar images, which were then cross-correlated to measure any time lag. This showed image B to lead image A by around a year, consistent with 410 days from the mass model. Although the similarity of the spectra and the detection of the lensing galaxy are the most compelling arguments for the classification of Q2138-431 as a gravitational lens, the time delay and mass-to-light ratio provide a consistent picture to support this conclusion. The wide separation of the quasar images and the simplicity of the mass model make Q2138-431 an excellent system for the measurement of the Hubble constant.

Convection has been discussed in the field of accretion discs for several decades, both as a means of angular momentum transport and also because of its role in controlling discs' vertical structure via heat transport. If the gas is sufficiently ionized and threaded by a weak magnetic field, convection might interact in non-trivial ways with the magnetorotational instability (MRI). Recently, vertically stratified local simulations of the MRI have reported considerable variation in the angular momentum transport, as measured by the stress to thermal pressure ratio $\alpha$, when convection is thought to be present. Although MRI turbulence can act as a heat source for convection, it is not clear how the instabilities will interact dynamically. Here we aim to investigate the interplay between the two instabilities in controlled numerical experiments, and thus isolate the generic features of their interaction. We perform vertically stratified, 3D MHD shearing box simulations with a perfect gas equation of state with the conservative, finite-volume code PLUTO. We find two characteristic outcomes of the interaction between the two instabilities: straight MRI and MRI/convective cycles, with the latter exhibiting alternating phases of convection-dominated flow (during which the turbulent transport is weak) and MRI-dominated flow. During the latter phase we find that $\alpha$ is enhanced by nearly an order of magnitude, reaching peak values of $\sim 0.08$. In addition, we find that convection in the non-linear phase takes the form of large-scale and oscillatory convective cells. Convection can also help the MRI persist to lower Rm than it would otherwise do. Finally we discuss how our results help interpret simulations of Dwarf Novae.

Inferring high-fidelity constraints on the spatial curvature parameter, $\Omega_{\rm K}$, under as few assumptions as possible, is of fundamental importance in cosmology. We propose a method to non-parametrically infer $\Omega_{\rm K}$ from late-Universe probes alone. Using Gaussian Processes (GP) to reconstruct the expansion history, we combine Cosmic Chronometers (CC) and Type Ia Supernovae (SNe~Ia) data to infer constraints on curvature, marginalized over the expansion history, calibration of the CC and SNe~Ia data, and the GP hyper-parameters. The obtained constraints on $\Omega_{\rm K}$ are free from parametric model assumptions for the expansion history, and are insensitive to the overall calibration of both the CC and SNe~Ia data (being sensitive only to relative distances and expansion rates). Applying this method to \textit{Pantheon} SNe~Ia and the latest compilation of CCs, we find $\Omega_{\rm K} = -0.03 \pm 0.26$, consistent with spatial flatness at the $\mathcal{O}(10^{-1})$ level, and independent of any early-Universe probes. Applying our methodology to future Baryon Acoustic Oscillations and SNe~Ia data from upcoming Stage IV surveys, we forecast the ability to constrain $\Omega_{\rm K}$ at the $\mathcal{O}(10^{-2})$ level.

Aims. We aim to investigate the I([CII]) versus I([NII]) integrated intensity behavior in the AF region in order to assess the [CII] emission contribution from the H II region, which is traced by [NII] line observations, and PDR components in the high-metallicity environment of the GC. Methods. We used [CII] 158 um and [NII] 205 um fine-structure line observations of the AF in the literature to compare their observational integrated intensity distribution to semi-theoretical predictions for the contribution of H II regions and adjacent PDRs to the observed [CII] emission. We explored variations in the [C/N] elemental abundance ratio to explain the overall behavior of the observed relationship. Based on our models, the H II region and PDR contributions to the observed [CII] emission is calculated for a few positions within and near to the AF. Estimates for the [C/N] abundance ratio and [N/H] nitrogen elemental abundance in the AF can then be derived. Results. The behavior of the I([CII]) versus I([NII]) relationship in the AF can be explained by model results satisfying 0.84 < [C/N]_AF < 1.41, with model metallicities ranging from 1 Z to 2 Z, hydrogen volume density log n(H) = 3.5, and ionization parameters log U from -1 to -2. A least-squares fit to the model data points yields log I([CII]) = 1.068log I([NII]) + 0.645 to predict the [CII] emission arising from the H II regions in the AF. The fraction of the total observed [CII] emission arising from within PDRs varies between ~ 0.20 and ~ 0.75. Our results yield average values for the carbon-to-nitrogen ratio and nitrogen elemental abundances of [C/N]_AF = 1.13 +/- 0.09 and [N/H]_AF = 6.21x10^4 for the AF, respectively. They are a factor of ~ 0.4 smaller and ~ 7.5 larger than their corresponding Galactic disk values.

The evolution of galaxies depends on their interaction with the surrounding environment. Ultra-diffuse galaxies (UDGs) have been found in large numbers in clusters. We detected a few star-forming blobs in the VESTIGE survey, located at $\sim$5 kpc from a UDG, namely NGVS 3543, in association with an HI gas cloud AGC 226178, suggesting a recent interaction between this low-surface-brightness system and the surrounding cluster environment. We use a complete set of multi-frequency data including deep optical, UV, and narrow-band H${\alpha}$ imaging and HI data to understand the formation process that gave birth to this peculiar system. For this purpose, we measured (i) the multi-wavelength radial surface brightness profiles of NGVS 3543 and compared them to the predictions of spectro-photometric models of galaxy evolution in rich clusters; and (ii) the aperture photometry of the blue regions in the vicinity of NGVS 3543 in order to determine their age and stellar mass. Comparisons of the observations with evolutionary models indicate that NGVS 3543 has undergone a ram-pressure stripping (RPS) that peaked $\sim$100 Myr ago, transforming a blue gas-rich UDG into a red gas-poor UDG. Star formation has taken place in the ram pressure stripped gas, the mass of which is $\sim$10$^8$ M$_{\odot}$, forming star complexes with a typical age of $\sim$20 Myr and a stellar mass of $\sim$10$^4$ M$_{\odot}$. These results suggest that we are observing for the first time the ongoing transformation of a gas-rich UDG into a red and quiescent UDG under the effect of a ram pressure stripping event. The same process could explain the lack of star-forming UDGs in rich environments observed in several nearby clusters.

We analyze the LIGO/Virgo GWTC-2 catalog to study the primary mass distribution of the merging black holes. We perform hierarchical Bayesian analysis, and examine whether the mass distribution has a sharp cutoff for primary black hole masses below $65 M_\odot$, as predicted in pulsational pair instability supernova model. We construct two empirical mass functions. One is a piece-wise function with two power-law segments jointed by a sudden drop. The other consists of a main truncated power-law component, a Gaussian component, and a third very massive component. Both models can reasonably fit the data and a sharp drop of the mass distribution is found at $\sim 50M_\odot$, suggesting that the majority of the observed black holes can be explained by the stellar evolution scenarios in which the pulsational pair-instability process takes place. On the other hand, the very massive sub-population, which accounts for at most several percents of the total, may be formed through hierarchical mergers or other processes.

Magnetic and energetic properties are presented for 17 dense cores within a few hundred pc of the Sun. Their plane-of-sky field strengths are estimated from the dispersion of polarization directions, following Davis, Chandrasekhar and Fermi (DCF). Their ratio of mass to magnetic critical mass is 0.5-3, indicating nearly critical field strengths. The field strength B_pos is correlated with column density N as B_pos~N^p, where p=1.05+-0.08, and with density n as B_pos~n^q, where q=0.66+-0.05. These magnetic properties are consistent with those derived from Zeeman studies (Crutcher et al. 2010), with less scatter. Relations between virial mass M_V, magnetic critical mass M_B, and Alfven amplitude sigma_B/B match the observed range of M/M_B for cores observed to be nearly virial, with M/M_V=0.5-2, with moderate Alfven amplitudes, and with sigma_B/B=0.1-0.4. The B-N and B-n correlations in the DCF and Zeeman samples can be explained when such bound, Alfvenic, and nearly-critical cores have central concentration and spheroidal shape. For these properties, B~N because M/M_B is nearly constant compared to the range of N, and B~n^(2/3) because M^(1/3) is nearly constant compared to the range of n^(2/3). The observed core fields which follow B~n^(2/3) need not be much weaker than gravity, in contrast to core fields which follow B~n^(2/3) due to spherical contraction at constant mass (Mestel 1966). Instead, the nearly critical values of M/M_B suggest that the observed core fields are nearly as strong as possible, among values which allow gravitational contraction.

We analyze spectropolarimetric data of the pre-cataclysmic variable binary system V471 Tau obtained with ESPaDOnS at the Canada-France-Hawaii Telescope in two observational campaigns (in Nov/Dec 2004 and Dec 2005). Using Zeeman-Doppler Imaging, we reconstruct the distribution of brightness map and large-scale magnetic field of the K2 dwarf at both epochs, as well as the amount of differential rotation by which surface maps are sheared. We detect significant fluctuations in the surface shear between the two campaigns. It goes from about twice the solar differential rotation rate to less than the solar value in a one-year interval. We conclude that the differential rotation fluctuations obtained for the K2 dwarf resemble those detected on the single-star analog AB Dor, although even larger amplitudes of variation are seen in the K2 dwarf of V471 Tau. Finally, we show that the differential rotation results obtained in this work do not favor an Applegate mechanism operating in the V471 Tau system, at least in its standard form, but leave room for explaining the observed orbital period fluctuations with exotic forms of similar phenomena based on dynamo processes operating within the convective zone of the K2 star.

At optical wavelengths, blazar Electric Vector Position Angle (EVPA) rotations linked with gamma-ray activity have been the subject of intense interest and systematic investigation for over a decade. One difficulty in the interpretation of EVPA rotations is the inherent 180{\deg} ambiguity in the measurements. It is therefore essential, when studying EVPA rotations, to ensure that the typical time-interval between successive observations - i.e. the cadence - is short enough to ensure that the correct modulo 180{\deg} value is selected. This optimal cadence depends on the maximum intrinsic EVPA rotation speed in blazars, which is currently not known. In this paper we address the questions of (i) the upper limit of rotation speeds for rotations greater than 90{\deg}, (ii) the observation cadence required to detect such rotations, (iii) whether rapid rotations have been missed in EVPA rotation studies thus far, (iv) what fraction of data is affected by the ambiguity, and (v) how likely detected rotations are affected by the ambiguity. We answer these questions with three seasons of optical polarimetric observations of a statistical sample of blazars sampled weekly with the RoboPol instrument and an additional season with daily observations. We model the distribution of EVPA changes on time scales from 1-3 days and estimate the fraction of changes exceeding 90{\deg}. We show that daily observations are necessary to measure >96% of optical EVPA variability in blazars correctly and that intra-day observations are needed to measure the fastest rotations that have been seen thus far.

In this work we first discuss the possibility that dark energy models with negative energy density values in the past can alleviate the $H_0$ tension, as well as the discrepancy with the BAO Ly-$\alpha$ data, both which prevail within the $\Lambda$CDM model. We then investigate whether two minimal extensions of the $\Lambda$CDM model, together or separately, can successfully realize such a scenario: (i) The spatial curvature, which, in the case of spatially closed universe, mimics a negative density source. (ii) Simple-graduated dark energy (-gDE), which promotes the null inertial mass density of the usual vacuum energy to an arbitrary constant -- if negative, the corresponding energy density decreases with redshift similar to the phantom models, but unlike them crosses below zero at a certain redshift. We find that, when the Planck data are not included in the observational analysis, the models with simple-gDE predict interesting and some significant deviations from the $\Lambda$CDM model. In particular, a spatially closed universe along with a simple-gDE of positive inertial mass density, which work in contrast to each other, results in minor improvement to the $H_0$ tension. The joint data set, including the Planck data, presents no evidence for a deviation from spatial flatness, but almost the same evidence for a cosmological constant and the simple-gDE with an inertial mass density of order $\mathcal{O}(10^{-12})\,\rm eV^4$. The latter case predicts almost no deviation from the $\Lambda$CDM model up until today -- so that it results in no improvement regarding the BAO Ly-$\alpha$ data -- , except that it slightly aggravates the $H_0$ tension. We also study via dynamical analysis the history of the universe in the models, as the simple-gDE results in futures different than the de Sitter future of the $\Lambda$CDM model.

We use VANDELS spectroscopic data overlapping with the $\simeq$7 Ms Chandra Deep Field South survey to extend studies of high-mass X-ray binary systems (XRBs) in 301 normal star-forming galaxies in the redshift range $3 < z < 5.5$. Our analysis evaluates correlations between X-ray luminosities ($L_X$), star formation rates (SFR) and stellar metallicities ($Z_\star$) to higher redshifts and over a wider range in galaxy properties than hitherto. Using a stacking analysis performed in bins of both redshift and SFR for sources with robust spectroscopic redshifts without AGN signatures, we find convincing evolutionary trends in the ratio $L_X$/SFR to the highest redshifts probed, with a stronger trend for galaxies with lower SFRs. Combining our data with published samples at lower redshift, the evolution of $L_X$/SFR to $z\simeq5$ proceeds as $(1 + z)^{1.03 \pm 0.02}$. Using stellar metallicities derived from photospheric absorption features in our spectroscopic data, we confirm indications at lower redshifts that $L_X$/SFR is stronger for metal-poor galaxies. We use semi-analytic models to show that metallicity dependence of $L_X$/SFR alone may not be sufficient to fully explain the observed redshift evolution of X-ray emission from high-mass XRBs, particularly for galaxies with SFR $<30$ $M_\odot$ yr$^{-1}$. We speculate that the discrepancy may arise due to reduced overall stellar ages in the early Universe leading to higher $L_X$/SFR for the same metallicity. We use our data to define the redshift-dependent contribution of XRBs to the integrated X-ray luminosity density and, in comparison with models, find that the contribution of high-mass XRBs to the cosmic X-ray background at $z>6$ may be $\gtrsim 0.25$ dex higher than previously estimated.

We present a spatio-kinematical analysis of the CO~($J$=2$\rightarrow$1) line emission, observed with the Atacama Large Millimter/submillimter Array (ALMA), of the outflow associated with the most massive core, ALMA1, in the 70 $\mu$m dark clump G010.991$-$00.082. The position-velocity (P-V) diagram of the molecular outflow exhibits a peculiar $\mathsf{S}$-shaped morphology that has not been seen in any other star forming region. We propose a spatio-kinematical model for the bipolar molecular outflow that consists of a decelerating high-velocity component surrounded by a slower component whose velocity increases with distance from the central source. The physical interpretation of the model is in terms of a jet that decelerates as it entrains material from the ambient medium, which has been predicted by calculations and numerical simulations of molecular outflows in the past. One side of the outflow is shorter and shows a stronger deceleration, suggesting that the medium through which the jet moves is significantly inhomogeneous. The age of the outflow is estimated to be $\tau$$\approx$1300 years, after correction for a mean inclination of the system of $\approx$57$^{\circ}$.

We present the results of a search for stellar flares in the first data release from the Next Generation Transit Survey (NGTS). We have found 610 flares from 339 stars, with spectral types between F8 and M6, the majority of which belong to the Galactic thin disc. We have used the 13 second cadence NGTS lightcurves to measure flare properties such as the flare amplitude, duration and bolometric energy. We have measured the average flare occurrence rates of K and early to mid M stars and present a generalised method to measure these rates while accounting for changing detection sensitivities. We find that field age K and early M stars show similar flare behaviour, while fully convective M stars exhibit increased white-light flaring activity, which we attribute to their increased spin down time. We have also studied the average flare rates of pre-main sequence K and M stars, showing they exhibit increased flare activity relative to their main sequence counterparts.

The Extragalactic Distance Database (EDD) was created as a repository for high quality, redshift-independent distances. A key component of EDD is the Color Magnitude Diagrams/Tip of the Red Giant Branch (CMDs/TRGB) catalog, which provides information on the stellar content of nearby galaxies observed with the Hubble Space Telescope (HST). Here we provide a decadal update to this catalog, which has now doubled in size to over 500 galaxies. We highlight the additions to our data reduction and analysis techniques, and provide examples of the science that has been made possible with this large data set. We find the TRGB to be a reliable measure for distance, and we aim to extend its distance coverage with HST to every galaxy within 10 Mpc. In the near-future, the combination of the James Webb Space Telescope and the Nancy Grace Roman Space Telescope will dramatically increase the number of targets within our grasp.

The origins of the Galilean satellites - namely Io, Europa, Ganymede, and Callisto - is not fully understood yet. Here we use N-body numerical simulations to study the formation of Galilean satellites in a gaseous circumplanetary disk around Jupiter. Our model includes the effects of pebble accretion, gas-driven migration, and gas tidal damping and drag. Satellitesimals in our simulations first grow via pebble accretion and start to migrate inwards. When they reach the trap at the disk inner edge, scattering events and collisions take place promoting additional growth. Growing satellites eventually reach a multi-resonant configuration anchored at the disk inner edge. Our best match to the masses of the Galilean satellites is produced in simulations where the integrated pebble flux is 1e-3 MJ. These simulations typically produce between 3 and 5 satellites. In our best analogues, adjacent satellite pairs are all locked in 2:1 mean motion resonances. However, they have also moderately eccentric orbits (0.1), unlike the current real satellites. We propose that the Galilean satellites system is a primordial resonant chain, similar to exoplanet systems as TRAPPIST-1, Kepler-223, and TOI-178. Callisto was probably in resonance with Ganymede in the past but left this configuration - without breaking the Laplacian resonance - via divergent migration due to tidal planet-satellite interactions. These same effects further damped the orbital eccentricities of these satellites down to their current values (0.001). Our results support the hypothesis that Io and Europa were born with water-ice rich compositions and lost all/most of their water afterwards. Firmer constraints on the primordial compositions of the Galilean satellites are crucial to distinguish formation models.

Previous work has argued that atomic gas mass estimates of galaxies from 21 cm HI emission are systematically low due to a cold opaque atomic gas component. If true, this opaque component necessitates a ~35% correction factor relative to the mass from assuming optically-thin HI emission. These mass corrections are based on fitting HI spectra with a single opaque component model that produces a distinct "top-hat" shaped line profile. Here, we investigate this issue using deep, high spectral resolution HI VLA observations of M31 and M33 to test if these top-hat profiles are instead superpositions of multiple HI components along the line-of-sight. We fit both models and find that >80% of the spectra strongly prefer a multi-component Gaussian model while <2% prefer the single opacity-corrected component model. This strong preference for multiple components argues against previous findings of lines-of-sight dominated by only cold HI. Our findings are enabled by the improved spectral resolution (0.42 km/s), whereas coarser spectral resolution blends multiple components together. We also show that the inferred opaque atomic ISM mass strongly depends on the goodness-of-fit definition and is highly uncertain when the inferred spin temperature has a large uncertainty. Finally, we find that the relation of the HI surface density with the dust surface density and extinction has significantly more scatter when the inferred HI opacity correction is applied. These variations are difficult to explain without additionally requiring large variations in the dust properties. Based on these findings, we suggest that the opaque HI mass is best constrained by HI absorption studies.

We introduce a novel black hole mass function which realistically models the physics of star formation and pair instability supernova with a minimal number of parameters. Applying this to all events in the LIGO-Virgo GWTC-2 catalog, we detect a peak at M_BHMG = 74.8^{+4.3}_{-8.0} MS, followed by a break in the mass function. Repeating the analysis without the black holes from the event GW190521, we find this feature at M_BHMG = 55.4^{+3.0}_{-6.1} MS. The latter result establishes the edge of the anticipated "black hole mass gap" at a value compatible with the expectation from standard stellar structure theory, while the former result is ~ 20MS higher, which would have far-reaching implications if confirmed. Using Bayesian techniques, we establish that our mass function fits a new catalog of black hole masses approximately as well as the pre-existing phenomenological mass functions. We also remark on the implications of these results for constraining or discovering new phenomena in nuclear and particle physics.

We have identified a first group of 33 new candidates for symbiotic stars (SySt) of the accreting-only variety among the 600,255 stars so far observed by the GALAH high-resolution spectroscopic survey of the Southern Hemisphere, more than doubling the number of those previously known. GALAH aims to high latitudes and this offers the possibility to sound the Galaxy for new SySt away from the usual Plane and Bulge hunting regions. In this paper we focus on SySt of the M spectral type, showing an Halpha emission with a peak in excess of 0.5 above the adjacent continuum level, and not affected by coherent radial pulsations. These constraints will be relaxed in future studies. The 33 new candidate SySt were subjected to a vast array of follow-up confirmatory observations (X-ray/UV observations with the Swift satellite, search for optical flickering, presence of a near-UV upturn in ground-based photometric and spectroscopic data, radial velocity changes suggestive of orbital motion, variability of the emission line profiles). According to Gaia eDR3 parallaxes, the new SySt are located at the tip of the Giant Branch, sharing the same distribution in M(Ks) of the well established SySt. The accretion luminosities of the new SySt are in the range 1-10 Lsun, corresponding to mass-accretion rates of 0.1-1x10(-9) Msun/yr for WDs of 1 Msun. The M giant of one of the new SySt presents a large Lithium over-abundance.

Carbon is an essential element for life but its behavior during Earth's accretion is not well understood. Carbonaceous grains in meteoritic and cometary materials suggest that irreversible sublimation, and not condensation, governs carbon acquisition by terrestrial worlds. Through astronomical observations and modeling we show that the sublimation front of carbon carriers in the solar nebula, or the soot line, moved inward quickly so that carbon-rich ingredients would be available for accretion at 1 au after the first million years. On the other hand, geological constraints firmly establish a severe carbon deficit in Earth, requiring the destruction of inherited carbonaceous organics in the majority of its building blocks. The carbon-poor nature of the Earth thus implies carbon loss in its precursor material through sublimation within the first million years.

During the formation of terrestrial planets, volatile loss may occur through nebular processing, planetesimal differentiation, and planetary accretion. We investigate iron meteorites as an archive of volatile loss during planetesimal processing. The carbon contents of the parent bodies of magmatic iron meteorites are reconstructed by thermodynamic modelling. Calculated solid/molten alloy partitioning of C increases greatly with liquid S concentration and inferred parent body C concentrations range from 0.0004 to 0.11 wt.%. Parent bodies fall into 2 compositional clusters characterized by cores with medium, and low C/S. Both of these require significant planetesimal degassing, as metamorphic devolatilization on chondrite-like precursors is insufficient to account for their C depletions. Planetesimal core formation models, ranging from closed system extraction to degassing of a wholly molten body, show that significant open system silicate melting and volatile loss is required to match medium and low C/S parent body core compositions. Greater depletion in C relative to S is the hallmark of silicate degassing, indicating that parent body core compositions record processes that affect composite silicate/iron planetesimals. Degassing of bare cores stripped of their silicate mantles would deplete S with negligible C loss, and could not account for inferred parent body core compositions. Devolatilization during small-body differentiation is thus a key process in shaping the volatile inventory of terrestrial planets derived from planetesimals and planetary embryos.

An attempt is made to uncover the physical meaning and significance of the obscure Lanczos tensor field which is regarded as a potential of the Weyl field. Despite being a fundamental building block of any metric theory of gravity, the Lanczos tensor has not been paid proper attention as it deserves. By providing an elucidation on this tensor field through its derivation in some particularly chosen spacetimes, we try to find its adequate interpretation. Though the Lanczos field is traditionally introduced as a gravitational analogue of the electromagnetic 4-potential field, the performed study unearths its another feature - a relativistic analogue of the Newtonian gravitational force field. A new domain of applicability of the Lanczos tensor is introduced which corroborates this new feature of the tensor.

According to General Relativity (GR) a universe with a cosmological constant, Lambda, like ours, is trapped inside an event horizon r< sqrt(3/Lambda). What is outside? We show, using Israel (1967) junction conditions, that there could be a different universe outside. Our Universe looks like a Black Hole for an outside observer. Outgoing radial null geodesics can not escape our universe, but incoming photons can enter and leave an imprint on our CMB sky. We present a picture of such a fossil record from the analysis of CMB maps that agrees with the Black Hole universe predictions but challenge our understanding of the origin of the primordial universe.

Real scalar fields with attractive self-interaction may form self-bound states, called oscillons. These dense objects are ubiquitous in leading theories of dark matter and inflation; of particular interest are long-lived oscillons which survive past $14$ Gyr, offering dramatic astrophysical signatures into the present day. We introduce a new formalism for computing the properties of oscillons with improved accuracy, which we apply to study the internal structure of oscillons and to identify the physical mechanisms responsible for oscillon longevity. In particular, we show how imposing realistic boundary conditions naturally selects a near-minimally radiating solution, and how oscillon longevity arises from its geometry. Further, we introduce a natural vocabulary for the issue of oscillon stability, which we use to predict new features in oscillon evolution. This framework allows for new efficient algorithms, which we use to address questions of whether and to what extent long-lived oscillons are fine-tuned. Finally, we construct a family of potentials supporting ultra-long-lived oscillons, with lifetimes in excess of $10^{17}$ years.

We explore the possibility of discovering the mirror baryons and electrons of the Mirror Twin Higgs model in direct detection experiments, in a scenario in which these particles constitute a subcomponent of the observed DM. We consider a framework in which the mirror fermions are sub-nano-charged, as a consequence of kinetic mixing between the photon and its mirror counterpart. We consider both nuclear recoil and electron recoil experiments. The event rates depend on the fraction of mirror DM that is ionized, and also on its distribution in the galaxy. Since mirror DM is dissipative, at the location of the Earth it may be in the form of a halo or may have collapsed into a disk, depending on the cooling rate. For a given mirror DM abundance we determine the expected event rates in direct detection experiments for the limiting cases of an ionized halo, an ionized disk, an atomic halo and an atomic disk. We find that by taking advantage of the complementarity of the different experiments, it may be possible to establish not just the multi-component nature of mirror dark matter, but also its distribution in the galaxy. In addition, a study of the recoil energies may be able to determine the masses and charges of the constituents of the mirror sector. By showing that the mass and charge of mirror helium are integer multiples of those of mirror hydrogen, these experiments have the potential to distinguish the mirror nature of the theory. We also carefully consider mirror plasma screening effects, showing that the capture of mirror dark matter particles in the Earth has at most a modest effect on direct detection signals.

Precise information about the composition of the Earth's core is critical to understand planetary evolution and for discussing current hot topics in geodynamic behavior, such as core-mantle boundary heat flow. However, samples from deep in the Earth's interior are not available, so our knowledge is based on comparison of laboratory measurements with seismological observations, informed by meteorite composition, and indications of the Earth's core temperature. One of the most interesting results of such work has been the suggestion that Earth's inner core must contain light elements because the density of the core, as determined from seismological measurements, is lower than the density of pure iron, its main constituent, as determined from laboratory measurements and/or theoretical work: the density deficit is now considered to be ~4%. However, this conclusion relies critically on having an accurate pressure scale to relate lab generated pressures to geological pressures. Establishing such a scale has been the subject of intensive research but still involves significant extrapolation and approximations, especially at higher pressures. Further, a pressure scale to the multi-megabar pressures is indispensable for discussing super-Earth planets. Here we establish the first primary pressure scale extending to the multi-megabar pressures of Earth's core by measuring acoustic phonon velocities using inelastic scattering from a rhenium sample in a diamond anvil cell. Our new pressure scale agrees with previous primary scales at lower pressures and also shock compression experiments, but is significantly different from previous secondary and theoretical scales at Earth's core pressures: previous scales have overestimated, by at least 20%, laboratory pressures at 230 gigapascals. Our new scale suggests the density deficit of the inner core is ~9%, doubling the light-element content of the core.

An axion rotating in field space can produce dark photons in the early universe via tachyonic instability. This explosive particle production creates a background of stochastic gravitational waves that may be visible at pulsar timing arrays or other gravitational wave detectors. This scenario provides a novel history for dark photon dark matter. The dark photons may be warm at a level detectable in future 21-cm line surveys. For a consistent cosmology, the radial direction of the complex field containing the axion must be thermalized. We explore a concrete thermalization mechanism in detail and also demonstrate how this setup can be responsible for the generation of the observed baryon asymmetry.

Nuclear symmetry energy $E_{\rm{sym}}(\rho)$ at density $\rho$ is normally expanded or simply parameterized as a function of $\chi=(\rho-\rho_0)/3\rho_0$ in the form of $E_{\rm{sym}}(\rho)\approx S+L\chi+2^{-1}K_{\rm{sym}}\chi^2+6^{-1}J_{\rm{sym}}\chi^3+\cdots$ using its magnitude $S$, slope $L $, curvature $K_{\rm{sym}}$ and skewness $J_{\rm{sym}}$ at the saturation density $\rho_0$ of nuclear matter. Much progress has been made in recent years in constraining especially the $S$ and $L$ parameters using various terrestrial experiments and astrophysical observations. However, such kind of expansions/parameterizations do not converge at supra-saturation densities where $\chi$ is not small enough, hindering an accurate determination of high-density $E_{\rm{sym}}(\rho)$ even if its characteristic parameters at $\rho_0$ are all well determined by experiments/observations. By expanding the $E_{\rm{sym}}(\rho)$ in terms of a properly chosen auxiliary function $\Pi_{\rm{sym}}(\chi,\Theta_{\rm{sym}})$ with a parameter $\Theta_{\rm{sym}}$ fixed accurately by an experimental $E_{\rm{sym}}(\rho_{\rm{r}})$ value at a reference density $\rho_{\rm{r}}$, we show that the shortcomings of the $\chi$-expansion can be completely removed or significantly reduced in determining the high-density behavior of $E_{\rm{sym}}(\rho)$. In particular, using two significantly different auxiliary functions, we show that the new approach effectively incorporates higher $\chi$-order contributions and converges to the same $E_{\rm{sym}}(\rho)$ much faster than the conventional $\chi$-expansion at densities $\lesssim3\rho_0$. Several quantitative demonstrations using Monte Carlo simulations are given.

We study a generalized superconformal model that gives rise to a subcritical regime of D-term hybrid inflation. Formulating the model in a Jordan frame, the effective potential of the subcritical regime is derived in the Einstein frame. It turns out the inflaton-waterfall field dynamics leads to various types of inflaton potential. Consequently the tensor-to-scalar ratio is found to range from $10^{-4}$ ($10^{-3}$) to $0.1$ for get 60 (50) $e$-folds before the end of inflation.

Cosmological particle production caused by a time-dependent scalar field is commonly used in cosmology. In this paper, we analyze the possibility of direct asymmetry production by cosmological particle production. Our focus is the mechanism of asymmetry production when an interaction explicitly violates symmetry and its motion is rapid enough to create particles by itself. Combining the exact WKB analysis and the Landau-Zener transition, we analyze the mechanism of generating asymmetry in the decay of the pseudo-Nambu-Goldstone boson. We also point out that perturbation before the non-perturbative analysis may drastically change the structure of the Stokes lines of the theory. The Exact WKB can play an important role in avoiding such discrepancies.

The detections of gravitational waves (GW) by LIGO/Virgo collaborations provide various possibilities to physics and astronomy. We are quite sure that GW observations will develop a lot both in precision and in number owing to the continuous works for the improvement of detectors, including the expectation to the newly joined detector, KAGRA, and the planned detector, LIGO-India. In this occasion, we review the fundamental outcomes and prospects of gravitational wave physics and astronomy. We survey the development focusing on representative sources of gravitational waves: binary black holes, binary neutron stars, and supernovae. We also summarize the role of gravitational wave observations as a probe of new physics.

Nonuniform structure of low-density nuclear matter, known as nuclear pasta, is expected to appear not only in the inner crust of neutron stars but also in core-collapse supernova explosions and neutron-star mergers. We perform fully three-dimensional calculations of inhomogeneous nuclear matter and neutron-star matter in the low-density region using the Thomas-Fermi approximation. The nuclear interaction is described in the relativistic mean-field approach with the point-coupling interaction, where the meson exchange in each channel is replaced by the contact interaction between nucleons. We investigate the influence of nuclear symmetry energy and its density dependence on pasta structures by introducing a coupling term between the isoscalar-vector and isovector-vector interactions. It is found that the properties of pasta phases in the neutron-rich matter are strongly dependent on the symmetry energy and its slope. In addition to typical shapes like droplets, rods, slabs, tubes, and bubbles, some intermediate pasta structures are also observed in cold stellar matter with a relatively large proton fraction. We find that nonspherical shapes are unlikely to be formed in neutron-star crusts, since the proton fraction obtained in $\beta$ equilibrium is rather small. The inner crust properties may lead to a visible difference in the neutron-star radius.

Proton energization at magnetic discontinuities generated by phase-steepened fronts of parallel propagating, large-amplitude Alfv\'enic fluctuation is studied using hybrid simulations. We find that dispersive effects yield to the collapse of the wave via phase steepening and the subsequent generation of compressible fluctuations that mediate an efficient local energy transfer from the wave to the protons. Proton scattering at the steepened edges causes non-adiabatic proton perpendicular heating. Furthermore, the parallel electric field at the propagating fronts mediates the acceleration of protons along the mean field. A steady-state is achieved where proton distribution function displays a field-aligned beam at the Alfv\'en speed, and compressible fluctuations are largely damped. We discuss the implications of our results in the context of Alfv\'enic solar wind.

Stars with an initial mass of $\sim 7$-11 solar masses form degenerate oxygen-neon cores following carbon burning. Electron captures in such cores can trigger runaway oxygen burning, resulting in either a collapse or a thermonuclear explosion. We provide a detailed description of the formalism used in previous work and apply it to two further forbidden transitions that are relevant to degenerate oxygen-neon cores: the $4^+_\text{g.s.}\rightarrow{}2^+_1$ transition in $^{24}\text{Na}(e^-,\nu_e)^{24}\text{Ne}$ and the ${5/2^+_{\text{g.s.}} \rightarrow{} 1/2^+_{\text{g.s.}}}$ transition in $^{27}\text{Al}(e^-,\nu_e)^{27}\text{Mg}$. The relevant nuclear matrix elements are determined through shell model calculations and constraints from CVC theory. We then investigate the astrophysical impact using the stellar evolution code MESA and through timescale arguments. In the relevant temperature range, the forbidden transitions substantially reduce the threshold densities for $^{24}\text{Na}(e^-,\nu_e)^{24}\text{Ne}$ and $^{27}\text{Al}(e^-,\nu_e)^{27}\text{Mg}$. In the MESA models, $^{24}\text{Na}(e^-,\nu_e)^{24}\text{Ne}$ now occurs immediately following the onset of $^{24}\text{Mg}(e^-,\nu_e)^{24}\text{Na}$. The impact on the overall evolution is uncertain: this is due to known difficulties in accounting for convective instabilities triggered by the $A=24$ electron captures. The transition between $^{27}\text{Al}$ and $^{27}\text{Mg}$ may have a minor effect on the early evolution but is unlikely to affect the outcome. The studied transitions should be included when calculating weak interaction rates between $^{24}$Na and $^{24}$Ne for temperatures $\log_{10}(T[\text{K}])\lesssim8.5$ and between $^{27}$Al and $^{27}$Mg for $\log_{10}(T[\text{K}])\lesssim8.8$.