Papers for Monday, Nov 25 2024

Cosmic shear surveys serve as a powerful tool for mapping the underlying matter density field, including non-visible dark matter. A key challenge in cosmic shear surveys is the accurate reconstruction of lensing convergence ($\kappa$) maps from shear catalogs impacted by survey boundaries and masks, which seminal Kaiser-Squires (KS) method are not designed to handle. To overcome these limitations, we previously proposed the Accurate Kappa Reconstruction Algorithm (AKRA), a prior-free maximum likelihood map-making method. Initially designed for flat sky scenarios with periodic boundary conditions, AKRA has proven successful in recovering high-precision $\kappa$ maps from masked shear catalogs. In this work, we upgrade AKRA to AKRA 2.0 by integrating the tools designed for spherical geometry. This upgrade employs spin-weighted spherical harmonic transforms to reconstruct the convergence field over the full sky. To optimize computational efficiency, we implement a scale-splitting strategy that segregates the analysis into two parts: large-scale analysis on the sphere (referred to as AKRA-sphere) and small-scale analysis on the flat sky (referred to as AKRA-flat); the results from both analyses are then combined to produce final reconstructed $\kappa$ map. We tested AKRA 2.0 using simulated shear catalogs with various masks, demonstrating that the reconstructed $\kappa$ map by AKRA 2.0 maintains high accuracy. For the reconstructed $\kappa$ map in unmasked regions, the reconstructed convergence power spectrum $C_\kappa^{\rm{rec}}$ and the correlation coefficient with the true $\kappa$ map $r_\ell$ achieve accuracies of $(1-C_\ell^{\rm{rec}}/C_\ell^{\rm{true}}) \lesssim 1\%$ and $(1-r_\ell) \lesssim 1\%$, respectively. Our algorithm is capable of straightforwardly handling further issues such as inhomogeneous shape measurement noise, which we will address in subsequent analysis.

The cosmological upper bound on the total neutrino mass is the dominant limit on this fundamental parameter. Recent observations-soon to be improved-have strongly tightened it, approaching the lower limit set by oscillation data. Understanding its physical origin, robustness, and model-independence becomes pressing. Here, we explicitly separate for the first time the two distinct cosmological neutrino-mass effects: the impact on background evolution, related to the energy in neutrino masses; and the "kinematic" impact on perturbations, related to neutrino free-streaming. We scrutinize how they affect CMB anisotropies, introducing two effective masses enclosing $\textit{background}$ ($\sum m_\nu^\mathrm{Backg.}$) and $\textit{perturbations}$ ($\sum m_\nu^\mathrm{Pert.}$) effects. We analyze CMB data, finding that the neutrino-mass bound is mostly a background measurement, i.e., how the neutrino energy density evolves with time. The bound on the "kinematic" variable $\sum m_\nu^\mathrm{Pert.}$ is largely relaxed, $\sum m_\nu^\mathrm{Pert.} < 0.8\,\mathrm{eV}$. This work thus adds clarity to the physical origin of the cosmological neutrino-mass bound, which is mostly a measurement of the neutrino equation of state, providing also hints to evade such a bound.

We present a catalog of 35 new candidate (13 high confidence) isolated, young stellar systems within the Virgo galaxy cluster identified through a citizen science search of public optical and ultraviolet imaging. "Blue blobs" are a class of blue, faint, isolated, extremely low stellar mass, and metal-rich star-forming clouds embedded in the hot intracluster medium of the Virgo cluster. Only six blue blobs were known previously and here we confirm an additional six of our candidates through velocity and metallicity measurements from follow-up optical spectroscopy on the Hobby-Eberly Telescope (HET). Our 13 high confidence candidates (including the six confirmed) have properties consistent with prior known blue blobs and are inconsistent with being low-mass galaxies. Most candidates are concentrated in relatively dense regions, roughly following filamentary structures within the cluster, but avoiding its center. Three of our candidates are likely the stellar counterparts of known 'optically dark' clouds of neutral hydrogen in the cluster, while a further four are widely separated extensions to previously known blue blobs. The properties of our new candidates are consistent with previous conclusions that blue blobs likely originated from ram pressure stripping events, however, their locations in velocity--projected cluster-centric radius phase-space imply that their parent galaxies are not on their first infall into the cluster. Through our ongoing follow-up program with HET we aim to confirm additional candidates, however, detailed understanding of the stellar populations and star formation histories of blue blobs will require JWST observations.

Deuterium fractionation is a well-established evolutionary tracer in low-mass star formation, but its applicability to the high-mass regime remains an open question. The abundances and ratios of deuterated species have often been proposed as reliable evolutionary indicators for different stages of the high-mass star formation. We investigate the role of N$_2$H$^+$ and key deuterated molecules as tracers of the different stages of the high-mass star formation, and test whether their abundance ratios can serve as reliable evolutionary indicators. We conducted APEX observations of o-H$_2$D$^+$ (1$_{10}$-1$_{11}$), N$_2$H$^+$ (4-3), and N$_2$d$^+$ (3-2) in 40 high-mass clumps at different evolutionary stages, selected from the ATLASGAL survey. Molecular column densities ($N$) and abundances ($X$), were derived through spectral line modelling, both under local thermodynamic equilibrium (LTE) and non-LTE conditions. The $N$(o-H$_2$D$^+$) show the smallest deviation from LTE results when derived under non-LTE assumptions. In contrast, N$_2$D$^+$ shows the largest discrepancy between the $N$ derived from LTE and non-LTE. In all the cases discussed, we found that $X$(o-H$_2$D$^+$) decreases more significantly with time than in the case of $X$(N$_2$D$^+$); whereas $X$(N$_2$H$^+$) increases slightly. Therefore, the validity of the recently proposed $X$(o-H$_2$D$^+$)/$X$(N$_2$D$^+$) ratio as a reliable evolutionary indicator was not observed for this sample. While the deuteration fraction derived from N$_2$D$^+$ and N$_2$H$^+$ clearly decreases with clump evolution, the interpretation of this trend is complex, given the different distribution of the two tracers. Our results suggest that a careful consideration of the observational biases and beam-dilution effects are crucial for an accurate interpretation of the evolution of the deuteration process during the high-mass star formation process.

The UV continuum slope of galaxies, $\beta$, is a powerful diagnostic. Understanding the redshift evolution of $\beta$ and its dependence on key galaxy properties can shed light on the evolution of galaxy physical properties over cosmic time. In this study, we present $\beta$ measurements for 295 spectroscopically confirmed galaxies at $5.5<z<14.3$ selected primarily from JADES, where $\beta$ has been measured from high quality JWST NIRSpec/PRISM spectra. We find a median $\beta=-2.3$ across our full sample, and find mild increase in blueness of $\beta$ with increasing redshift and fainter UV magnitudes. Interestingly, we find evidence for the average $\beta$ at $z > 9.5$ to begin to redden, deviating from the trend observed at $z < 9.5$. By producing stacked spectra in bins of redshift and $\beta$, we derive trends between $\beta$ and dust attenuation, metallicity, ionization parameter, and stellar age indicators directly from spectra, finding a lack of dust attenuation to be the dominant driver of bluer $\beta$ values. We further report six galaxies with $\beta<-3.0$, which show a range of spectroscopic properties and signs of significant LyC photon leakage. Finally, we show that the redder $\beta$ values at $z > 9.5$ may require rapid build-up of dust reservoirs in the very early Universe or a significant contribution from the nebular continuum emission to the observed UV spectra, with the nebular continuum fraction depending on the gas temperatures and densities. Our modeling shows that in the absence of dust, nebular emission at $T > 15,000$ K can reproduce the range of $\beta$ that we see in our sample. Higher gas temperatures driven by hot, massive stars can boost the fraction of nebular continuum emission, potentially explaining the observed $\beta$ values as well as bright UV magnitudes seen across galaxies at $z > 10$.

In this article we study the nature of the recently identified populations of hot companions to red supergiant stars (RSGs). To this end, we compile the literature on the most well characterised systems with the aim of better understanding the hot companions identified with ultra-violet photometry and confirmed with Hubble Space Telescope spectra in the Local Group. We identify 9 systems with current masses greater than around 8 solar masses that have constraints on their orbital periods, which are in the range 3 to 75a. Antares (Alpha Sco) is the obvious outlier in this distribution, having an estimated orbital period of around 2000 a. Mass-ratio (q=M2/MRSG) estimates are available only for 5 of the compiled systems and range between 0.16 < q < 1. Ongoing efforts to identify and characterise hot companions to RSGs in the SMC have revealed 88 hot companions that have observational constraints free of contamination from the RSG component. We present a summary of a recently conducted HST UV spectroscopic survey that aims to characterise a subset of these companions. These companions show a flat-q distribution in the range 0.3 < q < 1.

The Vera C. Rubin Observatory Legacy Survey of Space and Time (LSST) will survey the southern sky to create the largest galaxy catalog to date, and its statistical power demands an improved understanding of systematic effects such as source overlaps, also known as blending. In this work we study how blending introduces a bias in the number counts of galaxies (instead of the flux and colors), and how it propagates into galaxy clustering statistics. We use the $300\,$deg$^2$ DC2 image simulation and its resulting galaxy catalog (LSST Dark Energy Science Collaboration et al. 2021) to carry out this study. We find that, for a LSST Year 1 (Y1)-like cosmological analyses, the number count bias due to blending leads to small but statistically significant differences in mean redshift measurements when comparing an observed sample to an unblended calibration sample. In the two-point correlation function, blending causes differences greater than 3$\sigma$ on scales below approximately $10'$, but large scales are unaffected. We fit $\Omega_{\rm m}$ and linear galaxy bias in a Bayesian cosmological analysis and find that the recovered parameters from this limited area sample, with the LSST Y1 scale cuts, are largely unaffected by blending. Our main results hold when considering photometric redshift and a LSST Year 5 (Y5)-like sample.

Upcoming surveys are likely to discover a new sample of interstellar objects (ISOs) within the Solar System, but questions remain about the origin and distribution of this population within the Galaxy. ISOs are ejected from their host systems with a range of velocities, spreading out into tidal streams - analogous to the stellar streams routinely observed from the disruption of star clusters and dwarf galaxies. We create a simulation of ISO streams orbiting in the Galaxy, deriving a simple model for their density distribution over time. We then construct a population model to predict the properties of the streams in which the Sun is currently embedded. We find that the number of streams encountered by the Sun is quite large, ~ 10^6 or more. However, the wide range of stream properties means that for reasonable future samples of ISOs observed in the Solar System, we may see ISOs from the same star ("siblings"), and we are likely to see ISOs from the same star cluster ("cousins"). We also find that ISOs are typically not traceable to their parent star, though this may be possible for ISO siblings. Any ISOs observed with a common origin will come from younger, dynamically colder streams.

Comparing how an asteroid appears in space to its ablation behavior during atmospheric passage and finally to the properties of associated meteorites represents the ultimate probe of small near-Earth objects. We present observations from the Lowell Discovery Telescope and from multiple meteor camera networks of 2022 WJ1, an Earth impactor which was disrupted over the North American Great Lakes on 19 November 2022. As far as we are aware, this is only the second time an Earth impactor has been specifically observed in multiple passbands prior to impact to characterize its composition. The orbits derived from telescopic observations submitted to the Minor Planet Center (MPC) and ground-based meteor cameras result in impact trajectories that agree to within 40 meters, but no meteorites have been found as of yet. The telescopic observations suggest a silicate-rich surface, and thus a moderate-to-high albedo, which results in an estimated size for the object of just D = 40 - 60 cm. Modeling the fragmentation of 2022 WJ1 during its fireball phase also suggests an approximate half-meter original size for the object as well as an ordinary chondrite-like strength. These two lines of evidence both support that 2022 WJ1 was likely an S-type condritic object and the smallest asteroid compositionally characterized in space. We discuss how best to combine telescopic and meteor camera datasets, how well these techniques agree, and what can be learned from studies of ultra-small asteroids.

We present arguments that the neutrinos observed by IceCube from the active galactic nucleus TXS~0506+056 may originate near its core and not in the blazar jet. The origin of the neutrinos is consistent with the mechanism that produces the neutrino flux observed from the active galaxies NGC~1068 and NGC~4151, but requires an Eddington luminosity cosmic ray flux to compensate for its larger distance. Like NGC~1068, the source is characterized by episodes of high X-ray emission and is gamma-ray-obscured during the 2014 burst, and there is evidence that this is also the case during the short burst in 2017 that produced IC-170922. The observations may be explained as a flux originating in an obscured core within $10 \sim 100$ Schwarzschild radii from the central black hole, which is not transparent to gamma rays from neutral pions accompanying the neutrinos.

Fuzzy dark matter (FDM) is an attractive dark matter candidate composed of ultralight particles. In this paper, toward a clear understanding of the core-halo relation in the FDM halos, we consider a simple model of the soliton-halo system, in which the self-gravitating soliton core is formed in the presence of Navarro-Frenk-White (NFW) halo potential as an external field. Solving numerically the Schrödinger-Poisson equation, the self-gravitating soliton is obtained as a ground-state solution, which is characterized by the two key parameters, i.e., size of soliton core and its strength of self-gravity relative to those of the NFW halo. Using our soliton-halo model, we investigate the properties of soliton cores found in cosmological simulation, and the key parameters characterizing these solitons are reconstructed in a self-consistent manner. Results suggest that (1) the soliton core properties depend critically on both the self-gravity of the soliton and the external potential of the host halo, and (2) the scatter observed in the core-halo relation cannot be explained solely by the one in the halo's concentration-mass relation, as previously suggested, but also significantly influenced by intrinsic features of the soliton core, potentially arising from local dynamics at the halo center. We also demonstrate that the FDM mass can be reconstructed from the simulation data characterizing the halo density profile, providing a basis for applying the model to observational studies.

The CompactObject package is an open-source software framework developed to constrain the neutron star equation of state (EOS) through Bayesian statistical inference. It integrates astrophysical observational constraints from X-ray timing, gravitational wave events, and radio measurements, as well as nuclear experimental constraints derived from perturbative Quantum Chromodynamics (pQCD) and Chiral Effective Field Theory ($\chi$EFT). The package supports a diverse range of EOS models, including meta-model like and several physics-motivated EOS models. It comprises three independent components: an EOS generator module that currently provides seven EOS choices, a Tolman-Oppenheimer-Volkoff (TOV) equation solver, that allows the determination of the Mass Radius and Tidal deformability as observables, and a comprehensive Bayesian inference workflow module, including a complete pipeline for implementing EOS Bayesian inference. Each component can be used independently in different scientific research contexts, such as nuclear physics and astrophysics. In addition, CompactObject is designed to work in synergy with existing software such as CompOSE, allowing the use of the CompOSE EOS database to extend the EOS options available.

While mass transfer in binary systems is a crucial aspect of binary evolution models, it remains far from understood. HD 352 is a spectroscopic binary exhibiting ellipsoidal variability, likely due to a tidally deformed giant donor filling its Roche lobe and transferring matter to a faint companion. Here, we analyse VLTI/PIONIER interferometric observations of the system, obtained between 2010 to 2020. We demonstrate that observations near the system's quadrature cannot be explained by simple symmetric disk models, but are consistent with the shape of a Roche-lobe-filling star. We think that this is the first case of tidal deformation of a red giant being observed directly, thanks to the interferometric technique. By combining our interferometric modeling results with the analysis of the optical spectrum, multi-frequency spectral energy distribution, and published radial velocities and light curves, we constrain the system parameters and show that HD 352 will likely soon enter the common envelope phase, although we cannot reject the hypothesis that it is undergoing stable mass transfer against theoretical predictions. This has important consequences for modeling a large class of binary systems. Additionally, our observations confirm that Roche-lobe-filling giants can be resolved with interferometry under favorable conditions. Such observations may help resolve the mass transfer dichotomy in systems like symbiotic binaries, where the predominant mass transfer mode remains unclear.

Developing an efficient code for large, multiscale astrophysical simulations is crucial in preparing the upcoming era of exascale computing. RAMSES is an astrophysical simulation code that employs parallel processing based on the Message Passing Interface (MPI). However, it has limitations in computational and memory efficiency when using a large number of CPU cores. The problem stems from inefficiencies in workload distribution and memory allocation that inevitably occur when a volume is simply decomposed into domains equal to the number of working processors. We present RAMSES-yOMP, which is a modified version of RAMSES designed to improve parallel scalability. Major updates include the incorporation of Open Multi-Processing into the MPI parallelization to take advantage of both the shared and distributed memory models. Utilizing this hybrid parallelism in high-resolution benchmark simulations with full prescriptions for baryonic physics, we achieved a performance increase of a factor of 2 in the total run-time, while using 75% less memory and 30% less storage compared to the original code, when using the same number of processors. These improvements allow us to perform larger or higher-resolution simulations than what was feasible previously.

In the inner regions of protoplanetary discs, ionization chemistry controls the fluid viscosity, and is thus key to understanding various accretion, outflow and planet formation processes. The ionization is driven by thermal and non-thermal processes in the gas-phase, as well as by dust-gas interactions that lead to grain charging and ionic and thermionic emission from grain surfaces. The latter dust-gas interactions are moreover a strong function of the grain size distribution. However, analyses of chemical networks that include ionic/thermionic emission have so far only considered grains of a single size (or only approximately treated the effects of a size distribution), while analyses that include a distribution of grain sizes have ignored ionic/thermionic emission. Here, we: (1) investigate a general chemical network, widely applicable in inner disc regions, that includes gas-phase reactions, ionic and thermionic emission, and an arbitrary grain size distribution; (2) present a numerical method to solve this network in equilibrium; and (3) elucidate a general method to estimate the chemical time-scale. We show that: (a) approximating a grain size distribution by an "effective dust-to-gas ratio" (as done in previous work) can predict significantly inaccurate grain charges; and (b) grain charging significantly alters grain collisional time-scales in the inner disc. For conditions generally found in the inner disc, this work facilitates: (i) calculation of fluid resistivities and viscosity; and (ii) inclusion of the effect of grain charging on grain fragmentation and coagulation (a critical effect that is often ignored).

We examine the quiescent fractions of massive galaxies in six $z\gtrsim3$ spectroscopically-confirmed protoclusters in the COSMOS field, one of which is newly confirmed and presented here. We report the spectroscopic confirmation of MAGAZ3NE~J100143+023021 at $z=3.122^{+0.007}_{-0.004}$ by the Massive Ancient Galaxies At $z>3$ NEar-infrared (MAGAZ3NE) survey. MAGAZ3NE~J100143+023021 contains a total of 79 protocluster members (28 spectroscopic and 51 photometric). Three spectroscopically-confirmed members are star-forming ultra-massive galaxies ($\log(M_{\star}/{\rm M}_\odot)>11$; UMGs), the most massive of which has $\log(M_{\star}/{\rm M}_\odot)=11.15^{+0.05}_{-0.06}$. Combining Keck/MOSFIRE spectroscopy and the COSMOS2020 photometric catalog, we use a weighted Gaussian kernel density estimator to map the protocluster and measure its total mass $2.25^{+1.55}_{-0.65}\times10^{14}~{\rm M}_{\odot}$ in the dense ``core'' region. For each of the six COSMOS protoclusters, we compare the quiescent fraction to the status of the central UMG as star-forming or quiescent. We observe that galaxies in these protoclusters appear to obey galactic conformity: elevated quiescent fractions are found in protoclusters with $UVJ$ quiescent UMGs and low quiescent fractions are found in protoclusters containing $UVJ$ star-forming UMGs. This correlation of star-formation/quiescence in UMGs and the massive galaxies nearby in these protoclusters is the first evidence for the existence of galactic conformity at $z>3$. Despite disagreements over mechanisms behind conformity at low redshifts, its presence at these early cosmic times would provide strong constraints on the physics proposed to drive galactic conformity.

Pebble accretion refers to the growth of planetary bodies through the accretion of pebble-sized particles. Pebbles are defined in terms of their aerodynamically size $\tau_s$, which describes the level of coupling to the disk gas. Observations confirms the presence of pebble-sized particles in both protoplanetary disks and the early solar system. Pebble accretion proceeds through the settling mechanism, where particles settle to the surface of the planet. This Chapter discusses the key aspects of the pebble accretion framework: the accretion regimes, the planet initiation mass, and the planet isolation masses. The accretion behavior of loosely coupled $\tau_s > 1$ particles, referred to as "large pebbles", is also examined. The pebble accretion probability, $\epsilon$, is shown to be a useful parameter for evaluating the efficiency of the process, though this quantity is not necessarily high. Distinctions between pebble and planetesimal accretion are outlined. Pebble accretion, in particular, can be a highly effective mechanism in dense rings, as witnessed with ALMA.

Reproducing the physical characteristics of ultra-faint dwarf galaxies (UFDs) in cosmological simulations is challenging, particularly with respect to stellar metallicity and galaxy size. To investigate these difficulties in detail, we conduct high-resolution simulations ($M_{\rm gas} \sim 60 \, M_{\odot}$, $M_{\rm DM} \sim 370 \, M_{\odot}$ ) on six UFD analogs ($M_{\rm vir} \sim 10^8 - 10^9 \, M_{\odot}$, $M_{\rm \star} \sim 10^3 - 2.1 \times 10^4 \, M_{\odot}$). Our findings reveal that the stellar properties of UFD analogs are shaped by diverse star-forming environments from multiple progenitor halos in the early Universe. Notably, our UFD analogs exhibit a better match to the observed mass-metallicity relation (MZR), showing higher average metallicity compared to other theoretical models. The metallicity distribution functions (MDFs) of our simulated UFDs lack high-metallicity stars ($[\rm Fe/H] > -2.0$) while containing low-metallicity stars ($[\rm Fe/H] < -4.0$). Excluding these low-metallicity stars, our results align well with the MDFs of observed UFDs. However, forming stars with higher metallicity ($-2.0 \leq [\rm Fe/H]_{\rm max} \leq -1.5$) remains a challenge due to the difficulty of sustaining metal enrichment during their brief star formation period before cosmic reionization. Additionally, our simulations show extended outer structures in UFDs, resulting from dry mergers between progenitor halos. To ensure consistency, we adopt the same fitting method commonly used in observations to derive the half-light radius. We find that this method tends to produce lower values compared to direct calculations and struggles to accurately describe the extended outer structures. To address this, we employ a two-component density profile to obtain structural parameters, finding that it better describes the galaxy shape, including both inner and outer structures.

The progenitors of Type II-P supernovae (SN) have been confirmed to be red supergiants. However, the upper mass limit of the directly probed progenitors is much lower than that predicted by current theories, and the accurate determination of the progenitor masses is key to understand the final fate of massive stars. Located at a distance of only 6.72 Mpc, the Type II-P SN 2024ggi is one of the closest SN in the last decade. Previous studies have analyzed its progenitor by direct detection, but the derived progenitor mass may be influenced by the very uncertain circumstellar extinction and pulsational brightness variability. In this work, we try to constrain the progenitor mass with an environmental analysis based on images from the Hubble Space Telescope. We found that stars in the progenitor environment have a uniform spatial distribution without significant clumpiness, and we derived the star formation history of the environment with a hierarchical Bayesian method. The progenitor is associated with the youngest population in the SN environment with an age of log($t$/yr) = 7.41 (i.e. 25.7 Myr), which corresponds to an initial mass of $10.2^{+0.06}_{-0.09}$ $M_\odot$. Our work provides an independent measurement of the progenitor mass, which is not affected by circumstellar extinction and pulsational brightness variability.

Asteroseismology has emerged as a powerful tool to unravel the intricate relationships between evolved stars and their planetary systems. In this study, we leverage this technique to investigate the evolutionary stages of five exoplanet host stars, each exhibiting solar-like oscillations. Building on our previous work that identified two host stars as red clump and red giant branch (RGB) stars, this study focuses on a new and broader sample. By precisely measuring asteroseismic parameters such as the period spacing of dipole gravity modes ($\Delta\Pi_{1}$), we provide definitive confirmation of these stars' evolutionary states as subgiants or RGB stars. These results are not only crucial for understanding the internal structures of evolved stars but also for predicting the eventual fate of their planetary companions, which may face engulfment as their host stars expand. This research highlights the profound role of asteroseismology in advancing our knowledge of planetary system evolution and opens new pathways for exploring how stellar evolution impacts planetary survival. Our findings set the stage for future studies on the dynamic fates of exoplanets, providing key insights into the intricate processes of stellar and planetary evolution.

We present starkiller, an open-source Python package for forward-modeling flux retrieval from integral field unit spectrograph (IFU) datacubes. Starkiller simultaneously provides stellar spectral classification, relative velocity, and line-of-sight extinction for all sources in a catalog, alongside a source-subtracted datacube. It performs synthetic difference imaging by simulating all catalog sources in the field of view, using the catalog for positions and fluxes to scale stellar models, independent of the datacube. This differencing method is particularly powerful for subtracting both point-sources and trailed or even streaked sources from extended astronomical objects. We demonstrate starkiller's effectiveness in improving observations of extended sources in dense stellar fields for VLT/MUSE observations of comets, asteroids and nebulae. We also show that starkiller can treat satellite-impacted VLT/MUSE observations. The package could be applied to tasks as varied as dust extinction in clusters and stellar variability; the stellar modeling using Gaia fluxes is provided as a standalone function. The techniques can be expanded to imagers and to other IFUs.

The solar system planets are benchmarks for the planet formation theory. Yet two paradigms coexist for the four terrestrial planets: the prolonged collisional growth among planetesimals lasting $>100$ million years (Myr) and the fast formation via planetesimals accreting pebbles within 10 Myr. Despite their dramatic difference, we can hardly tell which theory is more relevant to the true history of the terrestrial planets' formation. Here, we show that the Moon's origin puts stringent constraints on the pebble accretion scenario, rendering it less favourable. In the pebble accretion model, the one-off giant impact between proto-Earth and Theia rarely (probability $<$ 1\textperthousand) occurs at the right timing and configuration for the Moon formation. Even if a potential impact happens by chance, giant impact simulations reveal perfect mixing between proto-Earth and Theia, leaving no room for the observed primordial Earth mantle heterogeneity and the compositional difference, though small, between Earth and the Moon. Thus, the Earth-Moon system along other terrestrial planets should preferably form from chaotic collisional growth in the inner solar system.

We utilize a hybrid approach that integrates the traditional cross-correlation function (CCF) and machine learning to detect spectroscopic multi-systems, specifically focusing on double-line spectroscopic binary (SB2). Based on the ninth data release (DR9) of the Large Sky Area Multi-Object Fiber Spectroscopic Telescope (LAMOST), which includes a medium-resolution survey (MRS) containing 29,920,588 spectra, we identify 27,164 double-line and 3124 triple-line spectra, corresponding to 7096 SB2 candidates and 1903 triple-line spectroscopic binary (SB3) candidates, respectively, representing about 1% of the selection dataset from LAMOST-MRS DR9. Notably, 70.1% of the SB2 candidates and 89.6% of the SB3 candidates are newly identified. Compared to using only the traditional CCF technique, our method significantly improves the efficiency of detecting SB2, saves time on visual inspections by a factor of four.

Globally, Pulsar Timing Array (PTA) experiments have revealed evidence supporting an existing gravitational wave background (GWB) signal in the PTA data set. Apart from acquiring more observations, the sensitivity of PTA experiments can be increased by improving the accuracy of the noise modeling. In PTA data analysis, noise modeling is conducted primarily using Bayesian statistics, relying on the marginal likelihood and Bayes factor to assess evidence. We introduce generalized steppingstone (GSS) as an efficient and accurate marginal likelihood estimation method for the PTA-Bayesian framework. This method enables cheaper estimates with high accuracy, especially when comparing expensive models such as the Hellings-Downs (HD) model or the overlap reduction function model (ORF). We demonstrate the efficiency and the accuracy of GSS for model selection and evidence calculation by reevaluating the evidence of previous analyses from the North American Nanohertz Observatory for Gravitational Waves (NANOGrav) 15 yr data set and the European PTA (EPTA) second data release. We find similar evidence for the GWB compared to the one reported by the NANOGrav 15-year data set. Compared to the evidence reported for the EPTA second data release, we find a substantial increase in evidence supporting GWB across all data sets.

The nonlinear matter power spectrum in cosmology describes how matter density fluctuations vary with scale in the universe, providing critical insights into large-scale structure formation. The matter power spectrum includes both smooth regions and highly oscillatory features. Cosmologists rely on noisy, multi-resolution realizations of large N-body simulations to study these phenomena, which require appropriate smoothing techniques to learn about underlying structures. We introduce a Bayesian Deep Process Convolution (DPC) model that flexibly adapts its smoothness parameter across the input space, enabling it to capture both smooth and variable structure within a single framework. The DPC model leverages common patterns across related functions to improve estimation in regions with sparse data. Compared to existing methods, the DPC model offers superior accuracy and uncertainty quantification in simulated data, and qualitatively superior performance with the cosmological data. This methodology will be useful in cosmology and other fields requiring flexible modeling of smooth nonstationary surfaces.

GRB$\,$220831A is a gamma-ray burst (GRB) with a duration and spectral peak energy that places it at the interface between the distribution of long-soft and short-hard GRBs. In this paper, we present the multi-wavelength follow-up campaign to GRB$\,$220831A and its optical, near-infrared, X-ray and radio counterparts. Our deep optical and near-infrared observations do not reveal an underlying host galaxy, and establish that GRB$\,$220831A is observationally hostless to depth, $m_i\gtrsim26.6$ AB mag. Based on the Amati relation and the non-detection of an accompanying supernova, we find that this GRB is most likely to have originated from a collapsar at $z>2$, but it could also possibly be a compact object merger at $z<0.4$ with a large separation distance from its host galaxy. Regardless of its origin, we show that its optical and near-infrared counterpart departs from the evolution expected from a forward shock dominated synchrotron afterglow, exhibiting a steep post-break temporal powerlaw index of $-3.83^{+0.62}_{-0.79}$, too steep to be the jet-break. By analysing a range of models, we find that the observed steep departure from forward shock closure relations is likely due to an internal process producing either a flare or a plateau.

Under the assumption that they are standard(isable) candles, the lightcurves of Type Ia supernovae have been analyzed in the framework of the standard Friedmann-Lemaître-Robertson-Walker cosmology to conclude that the expansion rate of the Universe is accelerating due to dark energy. While the original claims in the late 1990s were made using overlapping samples of less than 100 supernovae in total, catalogues of nearly 2000 supernovae are now available. In light of recent developments such as the cosmic dipole anomaly and the larger than expected bulk flow in the local Universe (which does not converge to the Cosmic Rest Frame), we analyze the newer datasets using a Maximum Likelihood Estimator and find that the acceleration of the expansion rate of the Universe is unequivocally anisotropic. The associated debate in the literature highlights the artifices of using supernovae as standardisable candles, while also providing deeper insights into a consistent relativistic view of peculiar motions as departures from the Hubble expansion of the Universe. The effects of our being `tilted observers' embedded in a deep bulk flow may have been mistaken for cosmic acceleration.

Fast radio bursts (FRBs) are highly energetic events of short-duration intense radio emission, the origin of which remains elusive till date. Polarization of the FRB signals carry information about the emission source as well as the magneto-ionic media the signal passes through before reaching terrestrial radio telescopes. Currently known FRBs show a diverse range of polarization, sometimes with complex features, making it challenging to describe them in a unified model. FRB 20230708A and FRB 20210912A are two bright and highly polarized FRBs detected in the Commensal Real-time ASKAP Fast Transients (CRAFT) survey with the Australian Square Kilometre Array Pathfinder (ASKAP) that exhibit time-dependent conversion between linear and circular polarization as well as intra-burst (apparent) variation of Faraday rotation measure. We investigate the intra-burst temporal evolution of the polarization state of radio emission in these two events using the Poincaré sphere representation and find that the trajectories of the polarization state are well described by great circles on the Poincaré sphere. These polarization features may be signatures of a transition between two partially coherent orthogonal polarization modes or propagation through a birefringent medium. We find that the observed variations of the polarization states of these two FRBs are qualitatively consistent a magnetospheric origin of the bursts and the effects of propagation through a birefringent medium with linearly polarized modes in the outer magnetosphere or near-wind region of a neutron star.

Turbulent magnetic fields are to some extent a universal feature in astrophysical phenomena. Charged particles that encounter these turbulence get on average accelerated according to the so-called second-order Fermi process. However, in most astrophysical environments there are additional competing processes, such as different kinds of first-order energy changes and particle escape, that effect the resulting momentum distribution of the particles. In this work we provide to our knowledge the first semi-analytical solution of the isotropic steady-state momentum diffusion equation including continuous and catastrophic momentum changes that can be applied to any arbitrary astrophysical system of interest. Here, we adopt that the assigned magnetic turbulence is constrained on a finite range and the particle flux vanishes beyond these boundaries. Consequently, we show that the so-called pile-up bump -- that has for some special cases long been established -- is a universal feature of stochastic acceleration that emerges around the momentum $\chi_{\rm eq}$ where acceleration and continuous loss are in equilibrium if the particle's residence time in the system is sufficient at $\chi_{\rm eq}$. In general, the impact of continuous and catastrophic momentum changes plays a crucial role in the shape of the steady-state momentum distribution of the accelerated particles, where simplified unbroken power-law approximations are often not adequate.

Evidence has emerged for a stochastic signal correlated among 67 pulsars within the 15-year pulsar-timing data set compiled by the NANOGrav collaboration. Similar signals have been found in data from the European, Indian, Parkes, and Chinese PTAs. This signal has been interpreted as indicative of the presence of a nanohertz stochastic gravitational wave background. To explore the internal consistency of this result we investigate how the recovered signal strength changes as we remove the pulsars one by one from the data set. We calculate the signal strength using the (noise-marginalized) optimal statistic, a frequentist metric designed to measure correlated excess power in the residuals of the arrival times of the radio pulses. We identify several features emerging from this analysis that were initially unexpected. The significance of these features, however, can only be assessed by comparing the real data to synthetic data sets. After conducting identical analyses on simulated data sets, we do not find anything inconsistent with the presence of a stochastic gravitational wave background in the NANOGrav 15-year data. The methodologies developed here can offer additional tools for application to future, more sensitive data sets. While this analysis provides an internal consistency check of the NANOGrav results, it does not eliminate the necessity for additional investigations that could identify potential systematics or uncover unmodeled physical phenomena in the data.

High energy cosmic-rays generate air showers when they enter Earth's atmosphere. Ground-based gamma-ray astronomy is possible using either direct detection of shower particles at mountain altitudes, or with arrays of imaging air-Cherenkov telescopes (IACTs). Advances in the technique and larger collection areas have increased the rate at which air-shower events can be captured, and the amount of data produced by modern high-time-resolution Cherenkov cameras. Therefore, Data Volume Reduction (DVR) has become critical for such telescope arrays, ensuring that only useful information is stored long-term. Given the vast amount of raw data, owing to the highest resolution and sensitivity, the upcoming Cherenkov Telescope Array Observatory (CTAO) will need robust data reduction strategies to ensure efficient handling and analysis. The CTAO data rates needs be reduced from hundreds of Petabytes (PB) per year to a few PB/year. This paper presents algorithms tailored for CTAO but also applicable for other arrays, focusing on selecting pixels likely to contain shower light. It describes and evaluates multiple algorithms based on their signal efficiency, noise rejection, and shower reconstruction. With a focus on a time-based clustering algorithm which demonstrates a notable enhancement in the retention of low-level signal pixels. Moreover, the robustness is assessed under different observing conditions, including detector defects. Through testing and analysis, it is shown that these algorithms offer promising solutions for efficient volume reduction in CTAO, addressing the challenges posed by the array's very large data volume and ensuring reliable data storage amidst varying observational conditions and hardware issues.

In this paper we provide a detailed investigation of the energisation processes in two-dimensional, two and a half-dimensional and three-dimensional collapsing magnetic trap models. Using kinematic magnetohydrodynamic models of collapsing magnetic traps, we examine the importance of Fermi acceleration in comparison with betatron acceleration in these models. We extend previous work by investigating particle orbits in two-dimensional models without and with a guide field component and from full three-dimensional models. We compare the outcomes for the different models and how they depend on the chosen initial conditions. While in the literature betatron acceleration has been emphasised as the major mechanism for particle energisation in collapsing magnetic traps, we find that Fermi acceleration can play a significant role as well for particle orbits with suitable initial conditions.

We investigate the alignment of non-red early-type galaxies (ETGs) with blue or green colors within large-scale filaments and compare this alignment pattern with that of red ETGs. Our analysis reveals a significant alignment of the major axes of red ETGs with the orientations of their host cosmic filaments, consistent with prior research. In contrast, non-red ETGs show no significant alignment signal. This divergence in alignment behavior between non-red and red ETGs implies a distinct evolutionary path for non-red ETGs, suggesting a formation process that may be independent of galaxy mergers or that recent mergers experienced by non-red ETGs may not follow the direction of the filament but rather be more random or even perpendicular to the filament orientation.

We derive a family of similarity solutions to the nonlinear non-equilibrium Marshak wave problem for an inhomogeneous planar medium which is coupled to a time dependent radiation driving source. We employ the non-equilibrium gray diffusion approximation in the supersonic regime. The solutions constitute a generalization of the non-equilibrium nonlinear solutions that were developed recently for homogeneous media. Self-similar solutions are constructed for a power law time dependent surface temperature, a spatial power law density profile and a material model with power law temperature and density dependent opacities and specific energy density. The extension of the problem to non-homogeneous media enables the existence of similarity solutions for a general power law specific material energy. It is shown that the solutions exist for specific values of the temporal temperature drive and spatial density exponents, which depend on the material exponents. We also illustrate how the similarity solutions take various qualitatively different forms which are analyzed with respect to various parameters. Based on the solutions, we define a set of non-trivial benchmarks for supersonic non-equilibrium radiative heat transfer. The similarity solutions are compared to gray diffusion simulations as well as to detailed implicit Monte-Carlo and discrete-ordinate transport simulations in the optically-thick regime, showing a great agreement, which highlights the benefit of these solutions as a code verification test problem.

This paper presents the results of a joint radio and gamma-ray timing campaign on the nine millisecond pulsars (MSPs) discovered as part of the L-band targeted survey of Fermi-LAT sources performed in the context of the Transients and Pulsars with MeerKAT (TRAPUM) Large Survey Project. Out of these pulsars, eight are members of binary systems; of these eight, two exhibit extended eclipses of the radio emission. Using an initial radio timing solution, pulsations were found in the gamma rays for six of the targets. For these sources, a joint timing analysis of radio times of arrival and gamma-ray photons was performed, using a newly developed code that optimises the parameters through a Markov chain Monte Carlo (MCMC) technique. This approach has allowed us to precisely measure both the short- and long-term timing parameters. This study includes a proper motion measurement for four pulsars, which a gamma ray-only analysis would not have been sensitive to, despite the 15-year span of Fermi data.

TOI-396 is an F6V star ($V\approx6.4$) orbited by three transiting planets. The orbital periods of the two innermost planets are close to the 5:3 commensurability ($P_b \sim3.6$ d and $P_c \sim6.0$ d). To measure the masses of the three planets, refine their radii, and investigate whether planets b and c are in MMR, we carried out HARPS RV observations and retrieved photometric data from TESS. We extracted the RVs via a skew-normal fit onto the HARPS CCFs and performed an MCMC joint analysis of the Doppler measurements and transit photometry, while employing the breakpoint method to remove stellar activity from the RV time series. We also performed a thorough TTV dynamical analysis of the system. Our analysis confirms that the three planets have similar sizes: $R_b=2.004_{-0.047}^{+0.045}R_{\oplus}$; $R_c=1.979_{-0.051}^{+0.054}R_{\oplus}$; $R_d=2.001_{-0.064}^{+0.063}R_{\oplus}$. For the first time, we determine RV masses for TOI-396b and d: $M_b=3.55_{-0.96}^{+0.94}M_{\oplus}$ ($\rho_b=2.44_{-0.68}^{+0.69}$ g cm$^{-3}$) and $M_d=7.1\pm1.6M_{\oplus}$ ($\rho_d=4.9_{-1.1}^{+1.2}$ g cm$^{-3}$). Our results suggest a quite unusual system architecture, with the outermost planet being the densest. The Doppler reflex motion induced by TOI-396c remains undetected in our RV time series, likely due to the proximity of $P_c$ to the star's rotation period ($P_{\mathrm{rot}}=6.7\pm1.3$ d). We also discovered that TOI-396b and c display significant TTVs. While the TTV dynamical analysis returns a formally precise mass for TOI-396c ($M_{c,\mathrm{dyn}}=2.24^{+0.13}_{-0.67}M_{\oplus}$), the result might not be accurate owing to the poor sampling of the TTV phase. We also conclude that TOI-396b and c are close to-, but out of- the 5:3 MMR. Our numerical simulation suggests TTV semi-amplitudes of up to 5 hours over a temporal baseline of $\sim$5.2 years.

Two enigmatic gamma-ray features in the Galactic central region, known as Fermi Bubbles (FBs), were found from Fermi-LAT data. An energy release (e.g., by tidal disruption events in the Galactic center, GC), generates a cavity with a shock that expands into the local ambient medium of the Galactic halo. A decade or so ago, a phenomenological model of the FBs was suggested as a result of routine star disruptions by the supermassive black hole in the GC which might provide enough energy for large-scale structures, like the FBs. In 2020, analytical and numerical models of the FBs as a process of routine tidal disruption of stars near the GC were developed, which can provide enough cumulative energy to form and maintain large scale structures like the FBs. The disruption events are expected to be ten to hundred events per million years, providing the average power of energy release from the GC into the halo of 3E41 erg/s, which is needed to support the FBs. Analysis of the evolution of superbubbles in exponentially stratified disks concluded that the FB envelope would be destroyed by the Rayleigh-Taylor (RT) instabilities at late stages. The shell is composed of a swept-up gas of the bubble, whose thickness is much thinner in comparison to the size of the envelope. We assume that hydrodynamic turbulence is excited in the FB envelope by the RT instability. In this case, the universal energy spectrum of turbulence may be developed in the inertial range of wavenumbers of fluctuations (the Kolmogorov-Obukhov spectrum). From our model we suppose the power of the FBs is transformed partly into the energy of hydrodynamic turbulence in the envelope. If so, hydrodynamic turbulence may generate MHD-fluctuations, which accelerate cosmic rays there and generate gamma-ray and radio emission from the FBs. We hope that this model may interpret the observed nonthermal emission from the bubbles.

The observations of compact star inspirals from LIGO/Virgo combined with mass and radius measurements from NICER provide a valuable tool to study the highly uncertain equation of state (EOS) of dense matter at the densities characteristic of compact stars. In this work, we constrain the solid states of strange-cluster matter, called strangeon matter, as the putative basic units of the ground state of bulk strong matter using a Bayesian statistical method, incorporating the mass and radius measurements of PSR J0030+0451, PSR J0740+6620, and the recent data for the $1.4\ M_{\odot}$ pulsar PSR J0437-4751. We also include constraints from gravitational wave events GW170817 and GW190814. Under the prior assumption of a finite number of quarks in a strangeon, $N_{\rm q}$, our analysis reveals that current mass-radius measurements favor a larger $N_{\rm q}$. Specifically, the results support the scenario where a strangeon forms a stable bound state with $N_{\rm q}=18$, symmetric in color, flavor, and spin spaces, compared to the minimum $N_{\rm q}$ prior. The comparative analyses of the posterior EOS parameter spaces derived from three-parameter model and two-parameter model demonstrate a consistent prediction under identical observational constraints. In particular, our results indicate that the most probable values of the maximum mass are found to be $3.58^{+0.16}_{-0.12}\ M_{\odot}$ ($3.65^{+0.18}_{-0.16}\ M_{\odot}$) at $90\%$ confidence level for three-parameter (two-parameter) EOS considering the constraints of GW190814. The corresponding radii for $1.4\ M_{\odot}$ and $2.1\ M_{\odot}$ stars are $12.04^{+0.27}_{-0.31}~\rm km$ ($12.16^{+0.26}_{-0.31}~\rm km$) and $13.43^{+0.31}_{-0.32}~\rm km$ ($13.60^{+0.29}_{-0.34}~\rm km$), respectively. This result may impact interestingly on the research of multiquark states, which could improve our understanding of the nonperturbative strong force.

The interplay between atomic gas, the star-formation history of a galaxy and its environment are intrinsically linked, and we need to decouple these dependencies to understand their role in galaxy formation and evolution. In this paper, we analyse the star formation histories (SFHs) of 187 galaxies from the MIGHTEE-HI Survey Early Science Release data, focusing on the relationships between HI properties and star formation. A strong correlation emerges between a galaxy's HI-to-stellar mass ratio and the time of formation, alongside an inverse correlation between stellar mass and time of formation, regardless of the inferred SFH. Additionally, galaxies with lower stellar masses and higher HI-to-stellar mass ratios exhibit longer gas depletion times compared to more massive galaxies, which appear to have depleted their gas and formed stars more efficiently. This suggests that smaller, gas-rich galaxies have higher depletion times due to shallower potential wells and less efficient star formation. Furthermore, we explore the connection between spin-filament alignment and HI content. We find no significant correlation between peak star formation activity and proximity to filaments. However, we do find that the two galaxies in our sample within 1 Mpc of a filament have very low gas-depletion timescales and have their spin axis misaligned with the filament, suggestive of a link between the galaxy properties and proximity to a filament.

In galaxy survey analysis, the observed clustering statistics do not directly match theoretical predictions but rather have been processed by a window function that arises from the survey geometry including the sky footprint, redshift-dependent background number density and systematic weights. While window convolution of the power spectrum is well studied, for the bispectrum with a larger number of degrees of freedom, it poses a significant numerical and computational challenge. In this work, we consider the effect of the survey window in the tripolar spherical harmonic decomposition of the bispectrum and lay down a formal procedure for their convolution via a series expansion of configuration-space three-point correlation functions, which was first proposed by Sugiyama et al. (2019). We then provide a linear algebra formulation of the full window convolution, where an unwindowed bispectrum model vector can be directly premultiplied by a window matrix specific to each survey geometry. To validate the pipeline, we focus on the Dark Energy Spectroscopic Instrument (DESI) Data Release 1 (DR1) luminous red galaxy (LRG) sample in the South Galactic Cap (SGC) in the redshift bin $0.4 \leqslant z \leqslant 0.6$. We first perform convergence checks on the measurement of the window function from discrete random catalogues, and then investigate the convergence of the window convolution series expansion truncated at a finite of number of terms as well as the performance of the window matrix. This work highlights the differences in window convolution between the power spectrum and bispectrum, and provides a streamlined pipeline for the latter for current surveys such as DESI and the Euclid mission.

Aims: We computed a celestial reference frame (CRF) from Very Long Baseline Interferometry (VLBI) Global Observing System (VGOS) data after five years of regular observations (155 multi-baseline 24-hour VGOS sessions until 2024.0). In this paper we document the source selection and scheduling strategies for the individual sessions, and investigate the effect of using this new VGOS CRF in the analysis of individual geodetic VLBI sessions. We carried out several comparisons with ICRF3-SX, and with VIE2023sx CRF which includes VLBI S/X data until 2024.0. Furthermore, we studied the effect of more frequent estimations of tropospheric parameters on the estimated CRF in the current VGOS network. We evaluated the VIE2023-VG CRF in the geodetic analysis of VGOS sessions where the source positions were fixed to either the VIE2023-VG CRF or to ICRF3-SX. Results: The current VIE2023-VG CRF is built with 1.39 million VGOS group delays and includes 418 radio sources, where 172 sources (41%) are introduced in only four research and development sessions alone. We show that the VIE2023-VG CRF has excellent source position precision. The median formal error from the least-squares adjustment is 30 microas for right ascension (scaled by cosine of declination) and 47 microas for declination. In terms of systematic distortions versus ICRF3-SX, the largest terms in the vector spherical harmonics up to the degree and order two, reach in absolute values around 60 microas, caused by correlations between the individual terms. Because of the lack of observations in the southern hemisphere, a constraint for a zero slope in declination difference with respect to ICRF3-SX is imposed in the global adjustment. Therefore, VGOS should prioritize the development of southern stations in order to limit the need for such constraints on the frame.

The persistent BeXRBs are a class of High-Mass X-ray Binaries (HMXRBs), which are characterized by persistent low X-ray luminosities ($L_{\rm X} \sim 10^{34}$ erg s$^{-1}$) and wide ($P_{\rm orb} >$ 30 d), almost circular orbits. In these sources the NS is slowly rotating (with $P_{\rm spin}$ well above 100 s) and accretes matter directly from the wind of the companion Be star, without the formation of an accretion disk. Since the '90s, when the first four members of this class were identified, several other sources of the same type have been discovered and investigated. Thanks to follow-up XMM-Newton observations, we have verified that most of them share common spectral and timing properties, such as a pulsed fraction that does not vary with the photon energy and a hot (kT = 1-2 keV) blackbody spectral component which contributes for 20-40 % to the total flux and has a size consistent with the NS polar cap. Here we provide an overview of how XMM-Newton contributed to constrain the observational properties and the current understanding of this type of sources. We also report about the first results obtained with a very recent XMM-Newton observation of the poorly known BeXRB 4U 0728-25.

The Magellanic Stream has long been known to contain multiple HI strands and corresponding stellar populations are beginning to be discovered. Combining an H3-selected sample with stars drawn from the Gaia catalog, we trace stars along a sub-dominant strand of the Magellanic Stream, as defined by gas content, across 30$^\circ$ on the sky. We find that the dominant strand is devoid of stars with Galactocentric distance $\lesssim 55$ kpc while the subdominant strand shows a close correspondence to such stars. We conclude that (1) the two Stream strands have different origins, (2) they are likely only close in projection, (3) the subdominant strand is tidal in origin, and (4) the subdominant strand is composed of disk material, likely drawn from the disk of the Small Magellanic Cloud.

We introduce a novel orbit superposition method designed to reconstruct the stellar density structure, kinematics, and chemical abundance distribution of the entire Milky Way by leveraging 6D phase-space information from its resolved stellar populations, limited by the spatial coverage of APOGEE DR17.

We show, using the pseudo-$C_\ell$ technique, how to estimate cosmic shear and galaxy-galaxy lensing power spectra that are insensitive to the effects of multiple sources of lensing bias including source-lens clustering, magnification bias and obscuration effects. All of these effects are of significant concern for ongoing and near-future Stage-IV cosmic shear surveys. Their common attribute is that they all introduce a cosmological dependence into the selection of the galaxy shear sample. Here, we show how a simple adaptation of the pseudo-$C_\ell$ method can help to suppress these biases to negligible levels in a model-independent way. Our approach is based on making pixelised maps of the shear field and then using a uniform weighting of those shear maps when extracting power spectra. To produce unbiased measurements, the weighting scheme must be independent of the cosmological signal, which makes the commonly-used inverse-variance weighting scheme unsuitable for cosmic shear measurements. We demonstrate this explicitly. A frequently-cited motivation for using inverse-variance weights is to minimize the errors on the resultant power spectra. We find that, for a Stage-IV-like survey configuration, this motivation is not compelling: the precision of power spectra recovered from uniform-weighted maps is only very slightly degraded compared to those recovered from an inverse-variance analysis, and we predict no degradation in cosmological parameter constraints. We suggest that other 2-point statistics, such as real-space correlation functions, can be rendered equally robust to these lensing biases by applying those estimators to pixelised shear maps using a uniform weighting scheme.

The intense debate about the presence of methane in the Martian atmosphere has stimulated the study of methanogens adapted to terrestrial habitats that mimic Martian environments. We examinate the environmental conditions, energy sources and ecology of terrestrial methanogens thriving in deep crystalline fractures, sub-sea hypersaline lakes and subglacial water bodies considered as analogs of a hypothetical habitable Martian subsurface. We combine this information with recent data on the distribution of buried water or ice and radiogenic elements on Mars and with models of the subsurface thermal regime of this planet to identify a 4.3-8.8 km-deep regolith habitat at the mid-latitude location of Acidalia Planitia, that might fit the requirements for hosting putative Martian methanogens analogous to the methanogenic families Methanosarcinaceae and Methanomicrobiaceae.

The microhertz frequency band of gravitational waves probes the merger of supermassive black holes as well as many other gravitational wave phenomena. However, space-interferometry methods that use test masses would require substantial development of test-mass isolation systems to detect anticipated astrophysical events. We propose an approach that avoids inertial test masses by situating spacecraft in the low-acceleration environment of the outer Solar System. We show that for Earth-spacecraft and inter-spacecraft distances of $\gtrsim 10$ AU, the accelerations on the spacecraft would be sufficiently small to potentially achieve sensitivities determined by stochastic gravitational wave backgrounds. We further argue, for arm lengths of $10-30$ AU and $10$ Watt transmissions, that stable phase locks should be achievable with 20 cm mirrors or 5 m radio dishes. We discuss designs that send both laser beams and radio waves between the spacecraft, finding that despite the $\sim10^4\times$ longer wavelengths, even a design with radio transmissions could reach stochastic background-limited sensitivities at $\lesssim 0.3\times 10^{-4}$ Hz. Operating in the radio significantly reduces many spacecraft design tolerances. Our baseline concept requires two arms to do interferometry. However, if one spacecraft carries a clock with Allan deviations at $10^4$ seconds of $10^{-17}$, a comparable sensitivity could be achieved with a single arm. Finally, we discuss the feasibility of achieving similar gravitational wave sensitivities in a `Doppler tracking' configuration where the single arm is anchored to Earth.

We deploy a newly-generated set of geometric albedo spectral grids to examine the detectability of methane (CH4) in the reflected-light spectrum of an Earth-like exoplanet at visible and near-infrared wavelengths with a future exoplanet imaging mission. By quantifying the detectability as a function of signal-to-noise ratio (SNR) and molecular abundance, we can constrain the best methods of detection with the high-contrast space-based coronagraphy slated for the next generation telescopes such as the Habitable Worlds Observatory (HWO). We used 25 bandpasses between 0.8 and 1.5 microns. The abundances range from a modern-Earth level to an Archean-Earth level, driven by abundances found in available literature. We constrain the optimal 20%, 30%, and 40% bandpasses based on the effective SNR of the data, and investigate the impact of spectral confusion between CH4 and H2O on the detectability of each one. We find that a modern-Earth level of CH4 is not detectable, while an Archean Earth level of CH4 would be detectable at all SNRs and bandpass widths. Crucially, we find that CH4 detectability is inversely correlated with H2o abundance, with required SNR increasing as H2O abundance increases, while H2O detectability depends on CH4 abundance and selected observational wavelength, implying that science requirements for the characterization of Earth-like planet atmospheres in the VIS/NIR should consider the abundances of both species in tandem.

The ground-based measurement of gravitational waves (GW) from merging binary black holes (BBH) uniquely allows determination of spins of stellar-remnant black holes (BH), thereby offering insights into their formation mechanisms. The observed population of BBH mergers exhibits two intriguing peculiarities related to BH spins, namely, a positively biased distribution of effective spin parameter, $\chi_{\rm eff}$, and an apparent anti-correlation between merger mass ratio, $q$, and $\chi_{\rm eff}$. Here we investigate the potential mechanisms for such observed properties, in BBH mergers via isolated binary evolution. We synthesize BBH mergers with the fast binary evolution code BSE. The role of various physical assumptions is explored, including tidal spin-up, compact remnant mass, and mass transfer physics. We compare the properties of WR-BH binaries that formed through stable mass transfer (SMT) and common envelope evolution (CE). We find that both the asymmetry in $\chi_{\rm eff}$ distribution and the $\chi_{\rm eff}-q$ anti-correlation are natural outcomes of isolated-binary BBH formation with the standard assumptions on mass transfer physics. The anti-correlation is particularly pronounced for SMT-channel BBH mergers that experience a mass-ratio-reversal, i.e., those where the second-born BH is the more massive member. The anti-correlation arises from the dependence of orbital shrinking during mass transfer and the Roche lobe size on the system's mass ratio. This characteristic $\chi_{\rm eff}-q$ trend diminishes with increasing metallicity and when the isolated-binary BBH merger population is mixed with a significant contribution of dynamically formed BBH mergers. Our results demonstrate that isolated massive binary evolution via the SMT sub-channel can reproduce the observable BBH merger population, with characteristic signatures in mass, mass ratio, and spin distributions.[abr.]

The $\sim$5 Myr PDS 70 is the only known system with protoplanets residing in the cavity of the circumstellar disk from which they formed, ideal for studying exoplanet formation and evolution within its natal environment. Here we report the first spin constraint and C/O measurement of PDS 70b from Keck/KPIC high-resolution spectroscopy. We detected CO (3.8 $\sigma$) and H$_2$O (3.5 $\sigma$) molecules in the PDS 70b atmosphere via cross-correlation, with a combined CO and H$_2$O template detection significance of 4.2 $\sigma$. Our forward model fits, using BT-Settl model grids, provide an upper limit for the spin-rate of PDS 70b ($<$29 km s$^{-1}$). The atmospheric retrievals constrain the PDS 70b C/O ratio to ${0.28}^{+0.20}_{-0.12}$ ($<$0.63 under 95$\%$ confidence level) and a metallicity [C/H] of ${-0.2}^{+0.8}_{-0.5}$ dex, consistent with that of its host star. The following scenarios can explain our measured C/O of PDS 70b in contrast with that of the gas-rich outer disk (for which C/O $\gtrsim$ 1). First, the bulk composition of PDS 70b might be dominated by dust+ice aggregates rather than disk gas. Another possible explanation is that the disk became carbon-enriched $\textit{after}$ PDS 70b was formed, as predicted in models of disk chemical evolution and as observed in both very low mass star and older disk systems with $\textit{JWST}$/MIRI. Because PDS 70b continues to accrete and its chemical evolution is not yet complete, more sophisticated modeling of the planet and the disk, and higher quality observations of PDS 70b (and possibly PDS 70c), are necessary to validate these scenarios.

With an aim towards modeling cosmologies beyond the LCDM paradigm, we demonstrate the automatic construction of recombination history emulators while enforcing a prior of causal dynamics. These methods are particularly useful in the current era of precision cosmology, where extremely constraining datasets provide insights into a cosmological model dominated by unknown contents. Cosmic Microwave Background (CMB) data in particular provide a clean glimpse into the interaction of dark matter, baryons, and radiation in the early Universe, but interpretation of this data requires knowledge of the evolution of the ionization history of the Universe. The exploration of new physics with new CMB data will require fast and flexible calculation of this ionization history. We develop a differentiable machine learning model for recombination physics using a neural network ordinary differential equation model (Universal Differential Equations, UDEs), building towards automatic dimensionality reduction and the avoidance of manual tuning based on cosmological model.

The Penrose process, a process that transfers energy from a black hole to infinity, together with the BSW mechanism, which uses collisions of ingoing particles at the event horizon of a black hole to locally produce large amounts of energy, is studied in a combined description for a $d$ dimensional extremal Reissner-Nordström black hole spacetime with negative, zero, or positive cosmological constant, i.e., for an asymptotically anti-de Sitter (AdS), flat, or de Sitter (dS) spacetime. In an extremal Reissner-Nordström black hole background, in the vicinity of the horizon, several types of radial collisions between electrically charged particles can be considered. The most interesting one is between a critical particle, with its electric charge adjusted in a specific way, and a usual particle, as it gives a divergent center of mass frame energy locally, this being a favorable but not sufficient condition to extract energy from the black hole. To understand whether energy can be extracted in such a collisional Penrose process, we investigate in detail a collision between ingoing particles 1 and 2, from which particles 3 and 4 emerge, with the possibility that particle 3 can carry energy far out from the black hole horizon. One finds that the mass, energy, electric charge, and initial direction of motion of particle 3 can have different values, depending on the collision internal process, but these values lie within some range. Moreover, the energy of particle 3 can be arbitrarily high but not infinite, characterizing a super-Penrose process. It is also shown that particle 4 has negative energy, living in its own electric ergosphere before being engulfed by the event horizon. For zero cosmological constant the results do not depend on the number of dimensions, but they do for nonzero cosmological constant, which also introduces differences in the lower bound for the energy extracted.

Computer models are used as a way to explore complex physical systems. Stationary Gaussian process emulators, with their accompanying uncertainty quantification, are popular surrogates for computer models. However, many computer models are not well represented by stationary Gaussian processes models. Deep Gaussian processes have been shown to be capable of capturing non-stationary behaviors and abrupt regime changes in the computer model response. In this paper, we explore the properties of two deep Gaussian process formulations within the context of computer model emulation. For one of these formulations, we introduce a new parameter that controls the amount of smoothness in the deep Gaussian process layers. We adapt a stochastic variational approach to inference for this model, allowing for prior specification and posterior exploration of the smoothness of the response surface. Our approach can be applied to a large class of computer models, and scales to arbitrarily large simulation designs. The proposed methodology was motivated by the need to emulate an astrophysical model of the formation of binary black hole mergers.

Accurate waveform templates of binary black holes (BBHs) with eccentric orbits are essential for the detection and precise parameter estimation of gravitational waves (GWs). While SEOBNRE produces accurate time-domain waveforms for eccentric BBH systems, its generation speed remains a critical bottleneck in analyzing such systems. Accelerating template generation is crucial to data analysis improvement and valuable information extraction from observational data. We present SEOBNRE_AIq5e2, an innovative AI-based surrogate model that crafted to accelerate waveform generation for eccentric, spin-aligned BBH systems. SEOBNRE_AIq5e2 incorporates an advanced adaptive resampling technique during training, enabling the generation of eccentric BBH waveforms with mass ratios up to 5, eccentricities below 0.2, and spins $|\chi_z|$ up to 0.6. It achieves an impressive generation speed of 4.3 ms per waveform with a mean mismatch of $1.02 \times 10^{-3}$. With the exceptional accuracy and rapid performance, SEOBNRE_AIq5e2 emerges as a promising waveform template for future analysis of eccentric gravitational wave data.

The minimal masses and radii of proto-neutron stars during different stages of their evolution are investigated. In our work we focus on two stages, directly after the supernova shock wave moves outwards, where neutrinos are still captured in the core and the lepton per baryon ratio is fixed to $Y_L = 0.4$, and a few seconds afterwards, when all neutrinos have left the star. All nuclear equations of state used for this purpose fulfill the binding energy constraints from chiral effective field theory for neutron matter at zero temperature. We find for the neutrino-trapped case higher minimal masses than for the case when neutrinos have left the proto-neutron star. Thermal effects, here in the form of a given constant entropy per baryon $s$, have a smaller effect on increasing the minimal mass. The minimal proto-neutron star mass for the first evolutionary stage with $Y_L = 0.4$ and $s = 1$ amounts to $M_{min} \sim 0.62M_{\odot}$ and for the stage without neutrinos and $s = 2$ to $M_{min} \sim 0.22M_{\odot}$ rather independent on the nuclear equation of state used. We also study the case related to an accretion induced collapse of a white dwarf where the initial lepton fraction is $Y_L = 0.5$ and observe large discrepancies in the results of the different tables of nuclear equations of state used. Our finding points towards a thermodynamical inconsistent treatment of the nuclear liquid-gas phase transition for nuclear equations of state in tabular form demanding a fully generalized three-dimensional Gibbs construction for a proper treatment. Finally, we demonstrate that there is a universal relation for the increase of the proto-neutron star minimal mass with the lepton fraction for all nuclear equations of state used.

We present a systematic \textit{ab initio} study of the low-lying states in beryllium isotopes from $^7\text{Be}$ to $^{12}\text{Be}$ using nuclear lattice effective field theory with the N$^3$LO interaction. Our calculations achieve excellent agreement with experimental data for energies, radii, and electromagnetic properties. We introduce a novel, model-independent method to quantify nuclear shapes, uncovering a distinct pattern in the interplay between positive and negative parity states across the isotopic chain. Our geometrical analysis reveals prominent two-center cluster structures, the emergence of one-neutron halo, and complex nuclear molecular dynamics, underscoring the strong clustering features inherent to beryllium isotopes.

We consider gravitational particle production (GPP) of dark matter (DM) under supergravity framework, where $\alpha$-attractor inflation model is used. The particle spectrum is computed numerically and the dark matter number density is obtained. We show how the dark matter mass, gravitino mass and inflation model parameters modify the results, and find the corresponding reheating temperature which leads to sufficient DM production. In our setup, supergravity corrections suppress the efficiency of GPP, and make the isocurvature constraint much weaker compared with the normal case. With tensor to scalar ratio ranges from $10^{-3}-10^{-4}$, and dark matter mass from $10^{-2} m_\phi - m_\phi$, the required reheating temperature should be around $10^3 \textrm{GeV} - 10^7 \textrm{GeV}$.

We study the evolution of growing vacuum bubbles. The bubble walls interact with the surrounding fluid and may, consequently, reach a terminal velocity. If the mean free path of the particles in the fluid is much shorter than the bubble wall thickness, the fluid is locally in thermal equilibrium and the wall's terminal velocity can be determined by entropy conservation. On the other hand, if local thermal equilibrium inside the wall cannot be maintained, the wall velocity can be estimated from the pressure impacted by ballistic particle dynamics at the wall. We find that the latter case leads to slightly slower bubble walls. Expectedly, we find the largest differences in the terminal velocity when the fluid is entirely ballistic. This observation indicates that the non-equilibrium effects inside walls are relevant. To study bubble evolution, we perform hydrodynamic lattice simulations in the case of local thermal equilibrium and $N$-body simulations in the ballistic case to investigate the dynamical effects during expansion. Both simulations show that even if a stationary solution exists in theory it may not be reached depending on the dynamics of the accelerating bubble walls.