adsabs/SciX_UAT_keywords huggingface dataset:
Revealing the Formation of the Milky Way Nuclear Star Cluster via Chemo-dynamical Modeling

The Milky Way nuclear star cluster (MW NSC) has been used as a template to understand the origin and evolution of galactic nuclei and the interaction of nuclear star clusters with supermassive black holes. It is the only nuclear star cluster with a supermassive black hole where we can resolve individual stars to measure their kinematics and metal abundance to reconstruct its formation history. Here, we present results of the first chemo-dynamical model of the inner 1 pc of the MW NSC using metallicity and radial velocity data from the KMOS spectrograph on the Very Large Telescope. We find evidence for two kinematically and chemically distinct components in this region. The majority of the stars belong to a previously known supersolar metallicity component with a rotation axis perpendicular to the Galactic plane. However, we identify a new kinematically distinct subsolar metallicity component that contains about 7% of the stars and appears to be rotating faster than the main component with a rotation axis that may be misaligned. This second component may be evidence for an infalling star cluster or remnants of a dwarf galaxy, merging with the MW NSC. These measurements show that the combination of chemical abundances with kinematics is a promising method to directly study the MW NSC's origin and evolution.

Keywords: supermassive black holes; star clusters; metallicity; stellar dynamics; interstellar dynamics; evolved stars; active galactic nuclei; galactic center; milky way galaxy physics; galaxy structure; galaxy nuclei
Exploring and Validating Exoplanet Atmospheric Retrievals with Solar System Analog Observations

Solar system observations that serve as analogs for exoplanet remote sensing data can provide important opportunities to validate ideas and models related to exoplanet environments. Critically, and unlike true exoplanet observations, solar system analog data benefit from available high-quality ground- or orbiter-derived "truth" constraints that enable strong validations of exoplanet data interpretation tools. In this work, we first present a versatile atmospheric retrieval suite, capable of application to reflected light, thermal emission, and transmission observations spanning a broad range of wavelengths and thermochemical conditions. The tool-dubbed rfast-is designed, in part, to enable exoplanet mission concept feasibility studies. Following model validation, the retrieval tool is applied to a range of solar system analog observations for exoplanet environments. Retrieval studies using Earth reflected light observations from NASA's EPOXI mission provide a key proof of concept for exo-Earth direct imaging concept missions under development. Inverse modeling applied to an infrared spectrum of Earth from the Mars Global Surveyor Thermal Emission Spectrometer achieves good constraints on atmospheric gases, including many biosignature gases. Finally, retrieval analysis applied to a transit spectrum of Titan derived from the Cassini Visual and Infrared Mapping Spectrometer provides a proof of concept for interpreting more feature-rich transiting exoplanet observations from NASA's James Webb Space Telescope. In the future, solar system analog observations for exoplanets could be used to verify exoplanet models and parameterizations, and future exoplanet analog observations of any solar system worlds from planetary science missions should be encouraged.

Keywords: remote sensing; radiative transfer simulations; exoplanets; earth (planet); titan
Optimized Statistical Approach for Comparing Multi-messenger Neutron Star Data

The neutron star equation of state is now being constrained from a diverse set of multi-messenger data, including gravitational waves from binary neutron star mergers, X-ray observations of the neutron star radius, and many types of laboratory nuclear experiments. These measurements are often mapped to a common domain for comparison with one another or are used to constrain the predictions of theoretical equations of state. We explore here the statistical biases that can arise when such multi-messenger data are compared or combined across different domains. We find that placing Bayesian priors individually in each domain of measurement can lead to biased constraints. We present a new prescription for defining Bayesian priors consistently across different experiments, which will allow for robust cross-domain comparisons. Using the first two binary neutron star mergers as an example, we show that a uniform prior in the tidal deformability can produce inflated evidence for large radii, while a uniform prior in the radius points toward smaller radii. Finally, using this new prescription, we provide a status update on multi-messenger constraints on the neutron star radius.

Keywords: neutron stars; gravitational waves; high energy astrophysics; nuclear physics
A Tidally Induced Global Corrugation Pattern in an External Disk Galaxy Similar to the Milky Way

We study the two-dimensional (2D) line-of-sight velocity (Vlos) field of the low-inclination, late-type galaxy VV304a. The resulting 2D kinematic map reveals a global, coherent, and extended perturbation that is likely associated with a recent interaction with the massive companion VV304b. We use multiband imaging and a suite of test-particle simulations to quantify the plausible strength of in-plane flows due to nonaxisymmetric perturbations and show that the observed velocity flows are much too large to be driven either by a spiral structure or by a bar. We use fully cosmological hydrodynamical simulations to characterize the contribution from in- and off-plane velocity flows to the Vlos field of recently interacting galaxy pairs like the VV304 system. We show that, for recently perturbed low-inclination galactic disks, the structure of the residual velocity field, after subtraction of an axisymmetric rotation model, can be dominated by vertical flows. Our results indicate that the Vlos perturbations in VV304a are consistent with a corrugation pattern. Its Vlos map suggests the presence of a structure similar to the Monoceros ring seen in the Milky Way. Our study highlights the possibility of addressing important questions regarding the nature and origin of vertical perturbations by measuring the line-of-sight velocities in low-inclination nearby galaxies.

Keywords: galaxy stellar disks; disk galaxies; galaxy dynamics; galaxy kinematics
A Comprehensive Correction of the Gaia DR3 XP Spectra

By combining spectra from the CALSPEC and NGSL, as well as spectroscopic data from the LAMOST Data Release 7 (DR7), we have analyzed and corrected the systematic errors of the Gaia DR3 BP/RP (XP) spectra. The errors depend on the normalized spectral energy distribution (simplified by two independent "colors") and G magnitude. Our corrections are applicable in the range of approximately ‑0.5 < BP ‑ RP < 2, 3 < G < 17.5, and E(B ‑ V) < 0.8. To validate our correction, we conduct independent tests by comparisons with the MILES and LEMONY spectra. The results demonstrate that the systematic errors of BP ‑ RP and G have been effectively corrected, especially in the near-ultraviolet. The consistency between the corrected Gaia XP spectra and the MILES and LEMONY is better than 2% in the wavelength range of 336–400 nm and 1% in redder wavelengths. A global absolute calibration is also carried out by comparing the synthetic Gaia photometry from the corrected XP spectra with the corrected Gaia DR3 photometry. Our study opens up new possibilities for using XP spectra in many fields. A Python package is publicly available to do the corrections (doi:10.12149/101375 or https://github.com/HiromonGON/GaiaXPcorrection).

Keywords: flux calibration; calibration; spectroscopy; extinction
What Does the Geometry of the Hβ BLR Depend On?

We combine our dynamical modeling black-hole mass measurements from the Lick AGN Monitoring Project 2016 sample with measured cross-correlation time lags and line widths to recover individual scale factors, f, used in traditional reverberation-mapping analyses. We extend our sample by including prior results from Code for AGN Reverberation and Modeling of Emission Lines (CARAMEL) studies that have utilized our methods. Aiming to improve the precision of black-hole mass estimates, as well as uncover any regularities in the behavior of the broad-line region (BLR), we search for correlations between f and other AGN/BLR parameters. We find (i) evidence for a correlation between the virial coefficient ${\mathrm{log}}_{10}({f}_{\mathrm{mean},\sigma })$ and black-hole mass, (ii) marginal evidence for a similar correlation between ${\mathrm{log}}_{10}({f}_{\mathrm{rms},\sigma })$ and black-hole mass, (iii) marginal evidence for an anticorrelation of BLR disk thickness with ${\mathrm{log}}_{10}({f}_{\mathrm{mean},\mathrm{FWHM}})$ and ${\mathrm{log}}_{10}({f}_{\mathrm{rms},\mathrm{FWHM}})$ , and (iv) marginal evidence for an anticorrelation of inclination angle with ${\mathrm{log}}_{10}({f}_{\mathrm{mean},\mathrm{FWHM}})$ , ${\mathrm{log}}_{10}({f}_{\mathrm{rms},\sigma })$ , and ${\mathrm{log}}_{10}({f}_{\mathrm{mean},\sigma })$ . Last, we find marginal evidence for a correlation between line-profile shape, when using the root-mean-square spectrum, ${\mathrm{log}}_{10}{(\mathrm{FWHM}/\sigma )}_{\mathrm{rms}}$ , and the virial coefficient, ${\mathrm{log}}_{10}({f}_{\mathrm{rms},\sigma })$ , and investigate how BLR properties might be related to line-profile shape using CARAMEL models.

Keywords: active galaxies; active galactic nuclei; seyfert galaxies; reverberation mapping; supermassive black holes
How Ram Pressure Drives Radial Gas Motions in the Surviving Disk

Galaxy evolution can be dramatically affected by the environment, especially by the dense environment of a galaxy cluster. Recent observational studies show that massive galaxies undergoing strong ram-pressure stripping (RPS) have an enhanced frequency of nuclear activity. We investigate this topic using a suite of wind-tunnel hydrodynamical simulations of a massive M star = 1011 M ⊙ disk galaxy with 39 pc resolution and including star formation and stellar feedback. We find that RPS increases the inflow of gas to the galaxy center regardless of the wind impact angle. This increase is driven by the mixing of interstellar and nonrotating intracluster media at all wind angles, and by increased torque on the inner disk gas, mainly from local pressure gradients when the intracluster medium (ICM) wind has an edge-on component. In turn, the strong pressure torques are driven by rising ram pressure. We estimate the black hole (BH) accretion using Bondi-Hoyle and torque models, and compare it with the mass flux in the central 140 pc region. We find that the torque model predicts much less accretion onto the BH of a RPS galaxy than the Bondi-Hoyle estimator. We argue that both models are incomplete: the commonly used torque model does not account for torques caused by the gas distribution or local pressure gradients, while the Bondi-Hoyle estimator depends on the sound speed of the hot gas, which includes the ICM in stripped galaxies. An estimator that accounts for this missing physics is required to capture BH accretion in a RPS galaxy.

Keywords: active galactic nuclei; galaxy clusters; hydrodynamical simulations; supermassive black holes
A Data-scientific Noise-removal Method for Efficient Submillimeter Spectroscopy With Single-dish Telescopes

For submillimeter spectroscopy with ground-based single-dish telescopes, removing the noise contribution from the Earth's atmosphere and the instrument is essential. For this purpose, here we propose a new method based on a data-scientific approach. The key technique is statistical matrix decomposition that automatically separates the signals of astronomical emission lines from the drift noise components in the fast-sampled (1-10 Hz) time-series spectra obtained by a position-switching (PSW) observation. Because the proposed method does not apply subtraction between two sets of noisy data (i.e., on-source and off-source spectra), it improves the observation sensitivity by a factor of $\sqrt{2}$ . It also reduces artificial signals such as baseline ripples on a spectrum, which may also help to improve the effective sensitivity. We demonstrate this improvement by using the spectroscopic data of emission lines toward a high-redshift galaxy observed with a 2 mm receiver on the 50 m Large Millimeter Telescope. Since the proposed method is carried out offline and no additional measurements are required, it offers an instant improvement on the spectra reduced so far with the conventional method. It also enables efficient deep spectroscopy driven by the future 50 m class large submillimeter single-dish telescopes, where fast PSW observations by mechanical antenna or mirror drive are difficult to achieve.

Keywords: atmospheric effects; spectroscopy; astronomical methods; astronomy data reduction; millimeter astronomy; submillimeter astronomy
Fast-transient Searches in Real Time with ZTFReST: Identification of Three Optically Discovered Gamma-Ray Burst Afterglows and New Constraints on the Kilonova Rate

The most common way to discover extragalactic fast transients, which fade within a few nights in the optical, is via follow-up of gamma-ray burst and gravitational-wave triggers. However, wide-field surveys have the potential to identify rapidly fading transients independently of such external triggers. The volumetric survey speed of the Zwicky Transient Facility (ZTF) makes it sensitive to objects as faint and fast fading as kilonovae, the optical counterparts to binary neutron star mergers, out to almost 200 Mpc. We introduce an open-source software infrastructure, the ZTF REaltime Search and Triggering, ZTFReST, designed to identify kilonovae and fast transients in ZTF data. Using the ZTF alert stream combined with forced point-spread-function photometry, we have implemented automated candidate ranking based on their photometric evolution and fitting to kilonova models. Automated triggering, with a human in the loop for monitoring, of follow-up systems has also been implemented. In 13 months of science validation, we found several extragalactic fast transients independently of any external trigger, including two supernovae with post-shock cooling emission, two known afterglows with an associated gamma-ray burst (ZTF20abbiixp, ZTF20abwysqy), two known afterglows without any known gamma-ray counterpart (ZTF20aajnksq, ZTF21aaeyldq), and three new fast-declining sources (ZTF20abtxwfx, ZTF20acozryr, ZTF21aagwbjr) that are likely associated with GRB200817A, GRB201103B, and GRB210204A. However, we have not found any objects that appear to be kilonovae. We constrain the rate of GW170817-like kilonovae to R < 900 Gpc-3 yr-1 (95% confidence). A framework such as ZTFReST could become a prime tool for kilonova and fast-transient discovery with the Vera Rubin Observatory.

Keywords: transient detection; transient sources; optical astronomy; gamma-ray bursts; neutron stars
Data-constrained 3D Modeling of a Solar Flare Evolution: Acceleration, Transport, Heating, and Energy Budget

Solar flares are driven by the release of free magnetic energy and its conversion to other forms of energy-kinetic, thermal, and nonthermal. Quantification of partitions between these energy components and their evolution is needed to understand the solar flare phenomenon including nonthermal particle acceleration, transport, and escape as well as the thermal plasma heating and cooling. The challenge of remote-sensing diagnostics is that the data are taken with finite spatial resolution and suffer from line-of-sight (LOS) ambiguity including cases when different flaring loops overlap and project one over the other. Here, we address this challenge by devising a data-constrained evolving 3D model of a multiloop SOL2014-02-16T064620 solar flare of GOES class C1.5. Specifically, we employed a 3D magnetic model validated earlier for a single time frame and extended it to cover the entire flare evolution. For each time frame we adjusted the distributions of the thermal plasma and nonthermal electrons in the model so that the observables synthesized from the model matched the observations. Once the evolving model had been validated in this way, we computed and investigated the evolving energy components and other relevant parameters by integrating over the model volume. This approach removes the LOS ambiguity and permits us to disentangle contributions from the overlapping loops. It reveals new facets of electron acceleration and transport as well as of the heating and cooling of the flare plasma in 3D. We find signatures of substantial direct heating of the flare plasma not associated with the energy loss of nonthermal electrons.

Keywords: solar flares; solar activity; non-thermal radiation sources; solar radio emission; solar x-ray emission; solar extreme ultraviolet emission
Black Hole-Black Hole Total Merger Mass and the Origin of LIGO/Virgo Sources

The LIGO-Virgo-KAGRA (LVK) Collaboration has reported nearly 100 black hole (BH)-BH mergers. LVK provides estimates of rates, masses, effective spins, and redshifts for these mergers. Yet the formation channel(s) of the mergers remains uncertain. One way to search for a formation site is to contrast the properties of detected BH-BH mergers with different models of BH-BH merger formation. Our study is designed to investigate the usefulness of the total BH-BH merger mass and its evolution with redshift in establishing the origin of gravitational-wave sources. We find that the average intrinsic BH-BH total merger mass shows exceptionally different behaviors for the models that we adopt for our analysis. In the local universe (z = 0), the average merger mass changes from ${\overline{M}}_{\mathrm{tot},\mathrm{int}}\sim 25\,{M}_{\odot }$ for the common envelope binary evolution and open cluster formation channels, to ${\overline{M}}_{\mathrm{tot},\mathrm{int}}\sim 30\,{M}_{\odot }$ for the stable Roche lobe overflow binary channel, to ${\overline{M}}_{\mathrm{tot},\mathrm{int}}\sim 45\,{M}_{\odot }$ for the globular cluster channel. These differences are even more pronounced at larger redshifts. However, these differences are diminished when considering the LVK O3 detector sensitivity. A comparison with the LVK O3 data shows that none of our adopted models can match the data, despite the large errors on BH-BH masses and redshifts. We emphasize that our conclusions are derived from a small set of six models that are subject to numerous known uncertainties. We also note that BH-BH mergers may originate from a mix of several channels, and that other (than those adopted here) BH-BH formation channels may exist.

Keywords: black hole physics
The ALPINE-ALMA [C II] Survey: [C II] 158 μm Emission Line Luminosity Functions at z ∼ 4-6

We present the [C II] 158 μm line luminosity functions (LFs) at z ∼ 4-6 using the ALMA observations of 118 sources, which are selected to have UV luminosity M1500Å < -20.2 and optical spectroscopic redshifts in COSMOS and ECDF-S. Of the 118 targets, 75 have significant [C II] detections and 43 are upper limits. This is by far the largest sample of [C II] detections, which allows us to set constraints on the volume density of [C II] emitters at z ∼ 4-6. But because this is a UV-selected sample, we are missing [C II]-bright but UV-faint sources, making our constraints strict lower limits. Our derived LFs are statistically consistent with the z ∼ 0 [C II] LF at 108.25-109.75L⊙. We compare our results with the upper limits of the [C II] LF derived from serendipitous sources in the ALPINE maps. We also infer the [C II] LFs based on published far-IR and CO LFs at z ∼ 4-6. Combining our robust lower limits with these additional estimates, we set further constraints on the true number density of [C II] emitters at z ∼ 4-6. These additional LF estimates are largely above our LF at L[CII] > 109L⊙, suggesting that UV-faint but [C II]-bright sources likely make significant contributions to the [C II] emitter volume density. When we include all the LF estimates, we find that available model predictions underestimate the number densities of [C II] emitters at z ∼ 4-6. Finally, we set a constraint on the molecular gas mass density at z ∼ 4-6, with ρmol ∼ (2-7) × 107M⊙ Mpc-3. This is broadly consistent with previous studies.

Keywords: high-redshift galaxies; emission line galaxies; luminosity function; warm ionized medium; warm neutral medium; molecular gas
Precursors of the RNA World in Space: Detection of (Z)-1,2-ethenediol in the Interstellar Medium, a Key Intermediate in Sugar Formation

We present the first detection of (Z)-1,2-ethenediol, (CHOH)2, the enol form of glycolaldehyde, in the interstellar medium toward the G+0.693-0.027 molecular cloud located in the Galactic Center. We have derived a column density of (1.8 ± 0.1) × 1013 cm-2, which translates into a molecular abundance with respect to molecular hydrogen of 1.3 × 10-10. The abundance ratio between glycolaldehyde and (Z)-1,2-ethenediol is ~5.2. We discuss several viable formation routes through chemical reactions from precursors such as HCO, H2CO, CHOH, or CH2CHOH. We also propose that this species might be an important precursor in the formation of glyceraldehyde (HOCH2CHOHCHO) in the interstellar medium through combination with the hydroxymethylene (CHOH) radical.

Keywords: astrochemistry; pre-biotic astrochemistry; molecular clouds; galactic center; interstellar medium; interstellar molecules
Distant Echoes of the Milky Way's Last Major Merger

The majority of the Milky Way's stellar halo consists of debris from our galaxy's last major merger, the Gaia-Sausage-Enceladus (GSE). In the past few years, stars from the GSE have been kinematically and chemically studied in the inner 30 kpc of our galaxy. However, simulations predict that accreted debris could lie at greater distances, forming substructures in the outer halo. Here we derive metallicities and distances using Gaia DR3 XP spectra for an all-sky sample of luminous red giant stars, and map the outer halo with kinematics and metallicities out to 100 kpc. We obtain follow-up spectra of stars in two strong overdensities-including the previously identified outer Virgo Overdensity-and find them to be relatively metal rich and on predominantly retrograde orbits, matching predictions from simulations of the GSE merger. We argue that these are apocentric shells of GSE debris, forming 60-90 kpc counterparts to the 15-20 kpc shells that are known to dominate the inner stellar halo. Extending our search across the sky with literature radial velocities, we find evidence for a coherent stream of retrograde stars encircling the Milky Way from 50 to 100 kpc, in the same plane as the Sagittarius Stream but moving in the opposite direction. These are the first discoveries of distant and structured imprints from the GSE merger, cementing the picture of an inclined and retrograde collision that built up our galaxy's stellar halo.

Keywords: milky way stellar halo; stellar streams; galaxy mergers; milky way formation; milky way galaxy