adsabs/SciX_UAT_keywords huggingface dataset:
Keck NIRES Spectral Standards for L, T, and Y Dwarfs

We present medium-resolution (λ/Δλ = 2700), near-infrared spectral standards for field L0-L2, L4, and L7-Y0 dwarfs obtained with the Near-Infrared Echellette Spectrometer on the Keck II 10 m telescope. These standards allow for detailed spectral comparative analysis of cold brown dwarfs discovered through ongoing ground-based projects such as Backyard Worlds: Planet 9, and forthcoming space-based spectral surveys such as the James Webb Space Telescope, SPHEREx, Euclid, and the Nancy Grace Roman Space Telescope.

Keywords: brown dwarfs; l dwarfs; t dwarfs; y dwarfs; infrared spectroscopy; spectroscopy; standard stars
Variation in Path Lengths of Turbulent Magnetic Field Lines and Solar Energetic Particles

Modeling of time profiles of solar energetic particle (SEP) observations often considers transport along a large-scale magnetic field with a fixed path length from the source to the observer. Here, we point out that variability in the turbulent field line path length can affect the fits to SEP data and the inferred mean free path and injection profile. To explore such variability, we perform Monte Carlo simulations in representations of homogeneous 2D MHD + slab turbulence adapted to spherical geometry and trace trajectories of field lines and full particle orbits, considering proton injection from a narrow or wide angular region near the Sun, corresponding to an impulsive or gradual solar event, respectively. We analyze our simulation results in terms of field line and particle path length statistics for 1° × 1° pixels in heliolatitude and heliolongitude at 0.35 and 1 au from the Sun, for different values of the turbulence amplitude b/B 0 and turbulence geometry as expressed by the slab fraction f s . Maps of the most probable path lengths of field lines and particles at each pixel exhibit systematic patterns that reflect the fluctuation amplitudes experienced by the field lines, which in turn relate to the local topology of 2D turbulence. We describe the effects of such path length variations on SEP time profiles, both in terms of path length variability at specific locations and the motion of the observer with respect to turbulence topology during the course of the observations.

Keywords: solar energetic particles; interplanetary magnetic fields; interplanetary turbulence; solar-terrestrial interactions
The Missing Satellite Problem outside of the Local Group. II. Statistical Properties of Satellites of Milky Way-like Galaxies

We present a new observation of satellite galaxies around seven Milky Way (MW)-like galaxies located outside of the Local Group (LG) using Subaru/Hyper Suprime-Cam imaging data to statistically address the missing satellite problem. We select satellite galaxy candidates using magnitude, surface brightness, Sérsic index, axial ratio, FWHM, and surface brightness fluctuation cuts, followed by visual screening of false positives such as optical ghosts of bright stars. We identify 51 secure dwarf satellite galaxies within the virial radius of nine host galaxies, two of which are drawn from the pilot observation presented in Paper I. We find that the average luminosity function of the satellite galaxies is consistent with that of the MW satellites, although the luminosity function of each host galaxy varies significantly. We observe an indication that more massive hosts tend to have a larger number of satellites. Physical properties of the satellites such as the size-luminosity relation are also consistent with the MW satellites. However, the spatial distribution is different; we find that the satellite galaxies outside of the LG show no sign of concentration or alignment, while that of the MW satellites is more concentrated around the host and exhibits a significant alignment. As we focus on relatively massive satellites with M V < -10, we do not expect that the observational incompleteness can be responsible here. This trend might represent a peculiarity of the MW satellites, and further work is needed to understand its origin.

Keywords: observational cosmology; dwarf galaxies; luminosity function
Rotational Variation Allows for Narrow Age Spread in the Extended Main-sequence Turnoff of Massive Cluster NGC 1846

The color-magnitude diagrams (CMDs) of intermediate-age star clusters (≲2 Gyr) are much more complex than those predicted by coeval, nonrotating stellar evolution models. Their observed extended main-sequence turnoffs (eMSTOs) could result from variations in stellar age, stellar rotation, or both. The physical interpretation of eMSTOs is largely based on the complex mapping between stellar models-themselves functions of mass, rotation, orientation, and binarity-and the CMD. In this paper, we compute continuous probability densities in three-dimensional color, magnitude, and ${v}_{{\rm{e}}}\sin i$ space for individual stars in a cluster's eMSTO, based on a rotating stellar evolution model. These densities enable the rigorous inference of cluster properties from a stellar model, or, alternatively, constraints on the stellar model from the cluster's CMD. We use the MIST stellar evolution models to jointly infer the age dispersion, the rotational distribution, and the binary fraction of the Large Magellanic Cloud cluster NGC 1846. We derive an age dispersion of ~70-80 Myr, approximately half the earlier estimates due to nonrotating models. This finding agrees with the conjecture that rotational variation is largely responsible for eMSTOs. However, MIST models do not provide a satisfactory fit to all stars in the cluster and achieve their best agreement at an unrealistically high binary fraction. The lack of agreement near the main-sequence turnoff suggests specific physical changes to the stellar evolution models, including a lower mass for the Kraft break and potentially enhanced main-sequence lifespans for rapidly rotating stars.

Keywords: star clusters; stellar evolution; stellar rotation; computational methods
The Spatial Clustering of ROSAT All-Sky Survey Active Galactic Nuclei. V. The Evolution of Broad-line AGN Clustering Properties in the Last 6 Gyr

This is the fifth paper in a series of investigations of the clustering properties of luminous, broad-emission-line active galactic nuclei (AGNs) identified in the ROSAT All-Sky Survey (RASS) and Sloan Digital Sky Survey (SDSS). In this work we measure the cross-correlation function (CCF) between RASS/SDSS Data Release 14 AGNs with the SDSS CMASS galaxy sample at 0.44 < z < 0.64. We apply halo occupation distribution (HOD) modeling to the CCF along with the autocorrelation function of the CMASS galaxies. We find that X-ray-selected and optically selected AGNs at 0.44 < z < 0.64 reside in statistically identical halos with a typical dark matter halo (DMH) mass of ${M}_{\mathrm{DMH}}^{\mathrm{typ},\mathrm{AGN}}\sim {10}^{12.7}\,{h}^{-1}\,{M}_{\odot }$ . The acceptable HOD parameter space for these two broad-line AGN samples have only statistically marginal differences caused by small deviations of the CCFs in the one-halo-dominated regime on small scales. In contrast to optically selected AGNs, the X-ray AGN sample may contain a larger population of satellites at M DMH ~ 1013 h -1 M ⊙. We compare our measurements in this work with our earlier studies at lower independent redshift ranges, spanning a lookback time of 6 Gyr. The comparison over this wider redshift range of 0.07 < z < 0.64 reveals (i) no significant difference between the typical DMH masses of X-ray-selected and optically selected AGNs, (ii) weak positive clustering dependencies of ${M}_{\mathrm{DMH}}^{\mathrm{typ},\mathrm{AGN}}$ with L X and M BH, (iii) no significant dependence of ${M}_{\mathrm{DMH}}^{\mathrm{typ},\mathrm{AGN}}$ on Eddington ratio, and (iv) the same DMH masses host more-massive accreting black holes at high redshift than at low redshifts.

Keywords: active galaxies; large-scale structure of the universe; x-ray active galactic nuclei
Cloudy in the Microcalorimeter Era: Improved Energies for Si and S K Fluorescence Lines

The upcoming X-ray missions based on the microcalorimeter technology require exquisite precision in spectral simulation codes in order to match the unprecedented spectral resolution. In this work, we improve the fluorescence K energies for Si IIXI and S IIXIII in the code Cloudy. In particular, we provide here a patch to update the Cloudy fluorescence energy table, originally based on Kaastra & Mewe, with the laboratory energies measured by Hell et al. The new Cloudy simulations were used to model the Chandra/HETG spectra of the High Mass X-ray Binary Vela X-1, showing a remarkable agreement and a dramatic improvement with respect to the current release version of Cloudy (C17.02).

Keywords: high energy astrophysics; x-ray astronomy; x-ray binary stars
Constraints on the Emission of Gamma-Rays from M31 with HAWC

Cosmic rays, along with stellar radiation and magnetic fields, are known to make up a significant fraction of the energy density of galaxies such as the Milky Way. When cosmic rays interact in the interstellar medium, they produce gamma-ray emission which provides an important indication of how the cosmic rays propagate. Gamma-rays from the Andromeda galaxy (M31), located 785 kpc away, provide a unique opportunity to study cosmic-ray acceleration and diffusion in a galaxy with a structure and evolution very similar to the Milky Way. Using 33 months of data from the High Altitude Water Cherenkov Observatory, we search for teraelectronvolt gamma-rays from the galactic plane of M31. We also investigate past and present evidence of galactic activity in M31 by searching for Fermi bubble-like structures above and below the galactic nucleus. No significant gamma-ray emission is observed, so we use the null result to compute upper limits on the energy density of cosmic rays >10 TeV in M31.

Keywords: high energy astrophysics; particle astrophysics; galactic cosmic rays; gamma-ray astronomy; andromeda galaxy
An SiO Toroid and Wide-angle Outflow Associated with the Massive Protostar W75N(B)-VLA2

We have carried out Atacama Large Millimeter/submillimeter Array observations of the massive star-forming region W75N(B), which contains the massive protostars VLA1, VLA2, and VLA3. Particularly, VLA2 is an enigmatic protostar associated with a wind-driven H2O maser shell, which has evolved from an almost isotropic outflow to a collimated one in just 20 yr. The shell expansion seemed to be halted by an obstacle located to the northeast of VLA2. Here we present our findings from observing the 1.3 mm continuum and H2CO and SiO emission lines. Within a region of ~30″ (~39,000 au) diameter, we have detected 40 compact millimeter continuum sources, three of them coinciding with VLA1, VLA2, and VLA3. While the H2CO emission is mainly distributed in a fragmented structure around the three massive protostars, but without any of the main H2CO clumps spatially coinciding with them, the SiO is highly concentrated on VLA2, indicating the presence of very strong shocks generated near this protostar. The SiO emission is clearly resolved into an elongated structure (~0.″6 × 0.″3; ~780 au×390 au) perpendicular to the major axis of the wind-driven maser shell. The structure and kinematics of the SiO emission are consistent with a toroid and a wide-angle outflow surrounding a central mass of ~10 M ⊙, thus supporting previous theoretical predictions regarding the evolution of the outflow. Additionally, we have identified the expected location and estimated the gas density of the obstacle that is hindering the expansion of the maser shell.

Keywords: protostars; stellar jets; radio continuum emission; circumstellar disks; stellar winds; star forming regions
Rotational Disruption of Dust Grains by Mechanical Torques for High-velocity Gas-Grain Collisions

Dust grains moving at hypersonic velocities of ${V}_{d}\gtrsim 100\,\mathrm{km}\,{{\rm{s}}}^{-1}$ through an ambient gas are known to be destroyed by nonthermal sputtering. Yet, previous studies of nonthermal sputtering disregarded the fact that dust grains can be spun up to suprathermal rotation by stochastic mechanical torques from gas-grain collisions. In this paper, we show that such grain suprathermal rotation can disrupt a small grain into small fragments because induced centrifugal stress exceeds the maximum tensile strength of grain material, Smax. We term this mechanism MEchanical Torque Disruption (METD). We find that METD is more efficient than nonthermal sputtering in destroying the smallest grains (a < 10 nm) of non-ideal structures, moving with velocities of ${V}_{d}\lt 500\,\mathrm{km}\,{{\rm{s}}}^{-1}$ . The ratio of rotational disruption to sputtering time is ${\tau }_{\mathrm{disr}}$ / ${\tau }_{\mathrm{sp}}\sim 0.7({S}_{\max }$ / ${10}^{9}\,\mathrm{erg}\,{\mathrm{cm}}^{-3})({\bar{A}}_{\mathrm{sp}}$ / $12){({Y}_{\mathrm{sp}}/0.1)(a/0.01\mu {\rm{m}})}^{3}{(300\mathrm{km}{{\rm{s}}}^{-1}/{V}_{d})}^{2}$ , where a is the radius of spherical grains and Ysp is the sputtering yield. We also consider the high-energy regime and find that the rate of METD is reduced and becomes less efficient than sputtering for ${V}_{d}\gt 500\,\mathrm{km}\,{{\rm{s}}}^{-1}$ because impinging particles only transfer part of their momentum to the grain. We finally discuss the implications of the METD mechanism for the destruction of hypersonic grains accelerated by radiation pressure, as well as grains in fast shocks. Our results suggest that the destruction of small grains by METD in fast shocks of supernova remnants may be more efficient than previously predicted by nonthermal sputtering, depending on grain internal structures.

Keywords: interstellar medium; interstellar dynamics; interstellar dust; interstellar dust processes
Jets from Accretion Disk Dynamos: Consistent Quenching Modes for Dynamo and Resistivity

Astrophysical jets are launched from strongly magnetized systems that host an accretion disk surrounding a central object. The origin of the magnetic field, which is a key component of the launching process, is still an open question. Here we address the question of how the magnetic field required for jet launching is generated and maintained by a dynamo process. By carrying out nonideal MHD simulations (PLUTO code), we investigate how the feedback of the generated magnetic field on the mean-field dynamo affects the disk and jet properties. We find that a stronger quenching of the dynamo leads to a saturation of the magnetic field at a lower disk magnetization. Nevertheless, we find that, while applying different dynamo feedback models, the overall jet properties remain unaffected. We then investigate a feedback model that encompasses a quenching of the magnetic diffusivity. Our modeling considers a more consistent approach for mean-field dynamo modeling simulations, as the magnetic quenching of turbulence should be considered for both a turbulent dynamo and turbulent magnetic diffusivity. We find that, after the magnetic field is saturated, the Blandford-Payne mechanism can work efficiently, leading to more collimated jets, which move, however, with slower speed. We find strong intermittent periods of flaring and knot ejection for low Coriolis numbers. In particular, flux ropes are built up and advected toward the inner disk thereby cutting off the inner disk wind, leading to magnetic field reversals, reconnection and, the emergence of intermittent flares.

Keywords: accretion; stellar jets; jets; magnetohydrodynamics; magnetohydrodynamical simulations; astrophysical fluid dynamics; high energy astrophysics; plasma astrophysics
VLT/MUSE Characterization of Dimorphos Ejecta from the DART Impact

We have observed the Didymos-Dimorphos binary system with the MUSE integral field unit spectrograph mounted at the Very Large Telescope before and after DART impact and captured the ensuing ejecta cone, debris cloud, and tails at subarcsecond resolutions. We targeted the Didymos system over 11 nights from 2022 September 26 to October 25 and utilized both narrow- and wide-field observations with and without adaptive optics, respectively. We took advantage of the spectral-spatial coupled measurements and produced both white-light images and spectral maps of the dust reflectance. We identified and characterized numerous dust features, such as the ejecta cone, spirals, wings, clumps, and tails. We found that the base of the sunward edge of the wings, from October 3 to 19, is consistent with maximum grain sizes on the order of 0.05-0.2 mm and that the earliest detected clumps have the highest velocities, on the order of ;10 m s-1. We also see that three clumps in narrow-field mode (8″ × 8″) exhibit redder colors and slower speeds, around 0.09 m s-1, than the surrounding ejecta, likely indicating that the clump is composed of larger, slower grains. We measured the properties of the primary tail and resolved and measured the properties of the secondary tail earlier than any other published study, with first retrieval on October 3. Both tails exhibit similarities in curvature and relative flux; however, the secondary tail appears thinner, which may be caused by lower-energy ejecta and possibly a low-energy formation mechanism such as secondary impacts.

Keywords: optical astronomy; asteroid satellites; apollo group; impact phenomena; ground telescopes
The X-shaped Radio Galaxy J0725+5835 is Associated with an AGN Pair

X-shaped radio galaxies (XRGs) are those that exhibit two pairs of unaligned radio lobes (main radio lobes and wings). One of the promising models for the peculiar morphology is jet reorientation. To clarify this, we conducted a 5 GHz observation with the European VLBI Network (EVN) of XRG J0725+5835, which resembles the archetypal binary active galactic nuclei (AGNs) 0402+379 in radio morphology, but it is larger in angular size. In our observation, two milliarcsecond-scale radio components with nonthermal radio emission are detected. Each of them coincides with an optical counterpart with similar photometric redshift and (optical and infrared) magnitude, corresponding to dual active nuclei. Furthermore, with the improved Very Large Array (VLA) images, we find a bridge between the two radio cores and a jet bending in the region surrounding the companion galaxy. This further supports the interplay between the main and companion galaxies. In addition, we also report the discovery of an arcsecond-scale jet in the companion. Given the projected separation of ~100 kpc between the main and companion galaxies, XRG J0725+5835 is likely associated with a dual jetted-AGN system. In both EVN and VLA observations, we find signatures that the jet is changing its direction, which is likely responsible for the X-shaped morphology. For the origin of jet reorientation, several scenarios are discussed.

Keywords: radio galaxies; active galactic nuclei; very long baseline interferometry; radio jets; interacting galaxies; galaxy pairs; galaxies
The PAndAS View of the Andromeda Satellite System. IV. Global Properties

We build a statistical framework to infer the global properties of the satellite system of the Andromeda galaxy (M31) from the properties of individual dwarf galaxies located in the Pan-Andromeda Archaelogical Survey (PAndAS) and the previously determined completeness of the survey. Using forward modeling, we infer the slope of the luminosity function of the satellite system, the slope of its spatial density distribution, and the size-luminosity relation followed by the dwarf galaxies. We find that the slope of the luminosity function is β = -1.5 ± 0.1. Combined with the spatial density profile, it implies that, when accounting for survey incompleteness, M31 hosts ${92}_{-26}^{+19}$ dwarf galaxies with M V < -5.5 and a sky-projected distance from M31 between 30 and 300 kpc. We conclude that many faint or distant dwarf galaxies remain to be discovered around Andromeda, especially outside the PAndAS footprint. Finally, we use our model to test if the higher number of satellites situated in the hemisphere facing the Milky Way could be explained simply by the detection limits of dwarf galaxy searches. We rule this out at >99.9% confidence and conclude that this anisotropy is an intrinsic feature of the M31 satellite system. The statistical framework we present here is a powerful tool to robustly constrain the properties of a satellite system and compare those across hosts, especially considering the upcoming start of the Euclid or Rubin large photometric surveys that are expected to uncover a large number of dwarf galaxies in the Local Volume.

Keywords: andromeda galaxy; dwarf galaxies; local group
High-angular-resolution Imaging of the V892 Tau Binary System: A New Circumprimary Disk Detection and Updated Orbital Constraints

We present a direct imaging study of V892 Tau, a young Herbig Ae/Be star with a close-in stellar companion and circumbinary disk. Our observations consist of images acquired via Keck II/NIRC2 with nonredundant masking and the pyramid wavefront sensor at $K^{\prime} $ band (2.12 μm) and $L^{\prime} $ band (3.78 μm). Sensitivity to low-mass accreting companions and cool disk material is high at $L^{\prime} $ band, while complimentary observations at $K^{\prime} $ band probe hotter material with higher angular resolution. These multiwavelength, multiepoch data allow us to differentiate the secondary stellar emission from disk emission and deeply probe the structure of the circumbinary disk at small angular separations. We constrain architectural properties of the system by fitting geometric disk and companion models to the $K^{\prime} $ - and $L^{\prime} $ -band data. From these models, we constrain the astrometric and photometric properties of the stellar binary and update the orbit, placing the tightest estimates to date on the V892 Tau orbital parameters. We also constrain the geometric structure of the circumbinary disk, and resolve a circumprimary disk for the first time.

Keywords: protoplanetary disks; interferometry; near infrared astronomy
A Stochastic Theory of the Hierarchical Clustering. II. Halo Progenitor Mass Function and Large-scale Bias

We generalize the stochastic theory of hierarchical clustering presented in Paper I by Lapi & Danese to derive the (conditional) halo progenitor mass function and the related large-scale bias. Specifically, we present a stochastic differential equation that describes fluctuations in the mass growth of progenitor halos of given descendant mass and redshift, as driven by a multiplicative Gaussian white noise involving the power spectrum and the spherical collapse threshold of density perturbations. We demonstrate that, as cosmic time passes, the noise yields an average drift of the progenitors toward larger masses, which quantitatively renders the expectation from the standard extended Press and Schechter (EPS) theory. We solve the Fokker-Planck equation associated with the stochastic dynamics, and obtain as an exact, stationary solution, the EPS progenitor mass function. Then we introduce a modification of the stochastic equation in terms of a mass-dependent collapse threshold modulating the noise, and solve analytically the associated Fokker-Planck equation for the progenitor mass function. The latter is found to be in excellent agreement with the outcomes of N-body simulations; even more remarkably, this is achieved with the same shape of the collapse threshold used in Paper I to reproduce the halo mass function. Finally, we exploit the above results to compute the large-scale halo bias, and find it in pleasing agreement with the N-body outcomes. All in all, the present paper illustrates that the stochastic theory of hierarchical clustering introduced in Paper I can describe effectively not only halos' abundance, but also their progenitor distribution and their correlation with the large-scale environment across cosmic times.

Keywords: cosmology; dark matter