adsabs/SciX_UAT_keywords huggingface dataset:
Learning Cosmology and Clustering with Cosmic Graphs

We train deep-learning models on thousands of galaxy catalogs from the state-of-the-art hydrodynamic simulations of the Cosmology and Astrophysics with MachinE Learning Simulations (CAMELS) project to perform regression and inference. We employ Graph Neural Networks (GNNs), architectures designed to work with irregular and sparse data, like the distribution of galaxies in the universe. We first show that GNNs can learn to compute the power spectrum of galaxy catalogs with a few percent accuracy. We then train GNNs to perform likelihood-free inference at the galaxy-field level. Our models are able to infer the value of Ωm with a ~12%-13% accuracy just from the positions of ~1000 galaxies in a volume of ${(25\,{h}^{-1}\,\mathrm{Mpc})}^{3}$ at z = 0 while accounting for astrophysical uncertainties as modeled in CAMELS. Incorporating information from galaxy properties, such as the stellar mass, stellar metallicity, and stellar radius, increases the accuracy to 4%-8%. Our models are built to be translation and rotation invariant, and they can extract information from any scale larger than the minimum distance between two galaxies. However, our models are not completely robust: testing on simulations run with a different subgrid physics than the ones used for training does not yield accurate results.

Keywords: neural networks; galaxies; cosmology; large-scale structure of the universe; computational methods
A Parsec-scale Catalog of Molecular Clouds in the Solar Neighborhood Based on 3D Dust Mapping: Implications for the Mass-Size Relation

We dendrogram the Leike et al. 3D dust map, leveraging its ~1 pc spatial resolution to produce a uniform catalog of molecular clouds in the solar neighborhood. Using accurate distances, we measure the properties of 65 clouds in true 3D space, eliminating much of the uncertainty in mass, size, and density. Clouds in the catalog contain a total of 1.1 × 105 M ⊙, span distances of 116-440 pc, and include a dozen well-studied clouds in the literature. In addition to deriving cloud properties in 3D volume density space, we create 2D dust extinction maps from the 3D data by projecting the 3D clouds onto a 2D "Sky" view. We measure the properties of the 2D clouds separately from the 3D clouds. We compare the scaling relation between the masses and sizes of clouds following Larson. We find that our 2D projected mass-size relation, M ∝ r 2.1, agrees with Larson's Third Relation, but our 3D derived properties lead to a scaling relation of about one order larger: M ∝ r 2.9. Validating predictions from theory and numerical simulations, our results indicate that the mass-size relation is sensitive to whether column or volume density is used to define clouds, since mass scales with area in 2D (M ∝ r 2) and with volume in 3D (M ∝ r 3). Our results imply a roughly constant column and volume density in 2D and 3D, respectively, for molecular clouds, as would be expected for clouds where the lower density, larger volume-filling gas dominates the cloud mass budget.

Keywords: molecular clouds; solar neighborhood; star forming regions; scaling relations
AI Can Identify Solar System Instability Billions of Years in Advance

Rare event schemes require an approximation of the probability of the rare event as a function of system state. Finding an appropriate reaction coordinate is typically the most challenging aspect of applying a rare event scheme. Here we develop an artificial intelligence (AI) based reaction coordinate that effectively predicts which of a limited number of simulations of the solar system will go unstable using a convolutional neural network classifier. The performance of the algorithm does not degrade significantly even 3.5 billion years before the instability. We overcome the class imbalance intrinsic to rare event problems using a combination of minority class oversampling, increased minority class weighting, and pulling multiple non-overlapping training sequences from simulations. Our success suggests that AI may provide a promising avenue for developing reaction coordinates without detailed theoretical knowledge of the system.

Keywords: planetary dynamics; solar system; mercury (planet); convolutional neural networks
The Aemulus Project. VI. Emulation of Beyond-standard Galaxy Clustering Statistics to Improve Cosmological Constraints

There is untapped cosmological information in galaxy redshift surveys in the nonlinear regime. In this work, we use the AEMULUS suite of cosmological N-body simulations to construct Gaussian process emulators of galaxy clustering statistics at small scales (0.1–50 h ‑1 Mpc) in order to constrain cosmological and galaxy bias parameters. In addition to standard statistics—the projected correlation function w p(r p), the redshift-space monopole of the correlation function ξ 0(s), and the quadrupole ξ 2(s)—we emulate statistics that include information about the local environment, namely the underdensity probability function P U(s) and the density-marked correlation function M(s). This extends the model of AEMULUS III for redshift-space distortions by including new statistics sensitive to galaxy assembly bias. In recovery tests, we find that the beyond-standard statistics significantly increase the constraining power on cosmological parameters of interest: including P U(s) and M(s) improves the precision of our constraints on Ωm by 27%, σ 8 by 19%, and the growth of structure parameter, f σ 8, by 12% compared to standard statistics. We additionally find that scales below ∼6 h ‑1 Mpc contain as much information as larger scales. The density-sensitive statistics also contribute to constraining halo occupation distribution parameters and a flexible environment-dependent assembly bias model, which is important for extracting the small-scale cosmological information as well as understanding the galaxy–halo connection. This analysis demonstrates the potential of emulating beyond-standard clustering statistics at small scales to constrain the growth of structure as a test of cosmic acceleration.

Keywords: large-scale structure of the universe; cosmological parameters; computational methods; astrostatistics
Constraints on Dynamical Dark Energy Models from the Abundance of Massive Galaxies at High Redshifts

We compare the maximal abundance of massive systems predicted in different dynamical dark energy (DDE) models at high redshifts z ≈ 4-7 with the measured abundance of the most massive galaxies observed to be already in place at such redshifts. The aim is to derive constraints for the evolution of the dark energy equation-of-state parameter w that are complementary to existing probes. We adopt the standard parameterization for the DDE evolution in terms of the local value w0 and of the lookback time derivative of the equation of state wa. We derive constraints on combinations of (w0, wa) in the different DDE models by using three independent probes: (i) the observed stellar mass function of massive objects at z ≥ 6 derived from the CANDELS survey; (ii) the estimated volume density of massive halos derived from the observation of massive, star-forming galaxies detected in the submillimeter range at z ≈ 4; (iii) the rareness of the most massive system (with an estimated gas mass exceeding 3 × 1011 M⊙) observed to be in place at z ≈ 7, a far-infrared-luminous object recently detected in the South Pole Telescope survey. Finally, we show that the combination of our results from the three above probes excludes a sizable fraction of the DDE parameter space wa ≳ -3/4 - (w0 + 3/2) presently allowed (or even favored) by existing probes.

Keywords: galaxy evolution; cosmological parameters; dark energy
Post-explosion Evolution of Core-collapse Supernovae

We investigate the post-explosion phase in core-collapse supernovae with 2D hydrodynamical simulations and a simple neutrino treatment. The latter allows us to perform 46 simulations and follow the evolution of the 32 explosion models during several seconds. We present a broad study based on three progenitors (11.2, 15, and 27 M⊙), different neutrino heating efficiencies, and various rotation rates. We show that the first seconds after shock revival determine the final explosion energy, remnant mass, and properties of ejected matter. Our results suggest that a continued mass accretion increases the explosion energy even at late times. We link the late-time mass accretion to initial conditions such as rotation strength and shock deformation at explosion time. Only some of our simulations develop a neutrino-driven wind (NDW) that survives for several seconds. This indicates that NDWs are not a standard feature expected after every successful explosion. Even if our neutrino treatment is simple, we estimate the nucleosynthesis of the exploding models for the 15 M⊙ progenitor after correcting the neutrino energies and luminosities to get a more realistic electron fraction.

Keywords: core-collapse supernovae; supernova dynamics; explosive nucleosynthesis; supernovae
Local Analogs to High-redshift Galaxies. I. Characterization of Dust Emission and Star Formation History

Star-forming dwarf galaxies have properties similar to those expected in high-redshift galaxies. Hence, these local galaxies may provide insights into the evolution of the first galaxies and the physical processes at work. We present a sample of 11 potential local analogs to high-z (LAHz) galaxies. The sample consists of blue compact dwarf galaxies, selected to have spectral energy distributions that fit galaxies at 1.5 < z < 4. We use SOFIA-HAWC+ observations combined with optical and near-infrared data to characterize the dust properties, star formation rate (SFR), and star formation histories (SFHs) of the sample of LAHz galaxies. We employ Bayesian analysis to characterize the dust using two-component blackbody models. Using the LIGHTNING package, we fit the spectral energy distribution of the LAHz galaxies over the far-UV-far-infrared wavelength range and derive the SFH in five time steps up to a look-back time of 13.3 Gyr. Of the 11 LAHz candidates, six galaxies have SFH consistent with no star formation activity at look-back times beyond 1 Gyr. The remaining galaxies show residual levels of star formation at ages ≳1 Gyr, making them less suitable as local analogs. The six young galaxies stand out in our sample by having the lowest gas-phase metallicities. They are characterized by warmer dust, having the highest specific SFR and the highest gas mass fractions. The young age of these six galaxies suggests that merging is less important as a driver of the star formation activity. The six LAHz candidates are promising candidates for studies of the gasdynamics role in driving star formation.

Keywords: blue compact dwarf galaxies; star formation; dust continuum emission; interstellar medium
The Effect of Flow and Magnetic Twist on Resonant Absorption of Slow MHD Waves in Magnetic Flux Tubes

Observations show that there are twisted magnetic flux tubes and plasma flow throughout the solar atmosphere. The main purpose of this work is to obtain the damping rate of sausage modes in the presence of magnetic twist and plasma flow. We obtain the dispersion relation for sausage modes in slow continuity in an inhomogeneous layer under the conditions of magnetic pores, then we solve it numerically. For the selected density profile, the magnetic field, and the plasma flow as a function of radius across the inhomogeneous layer, we show that the effect of the twisted magnetic field on the resonance absorption at low speed of the plasma flow is greater than one at high speed.

Keywords: solar physics; solar photosphere; solar atmosphere
Subaru High-z Exploration of Low-luminosity Quasars (SHELLQs). XIV. A Candidate Type II Quasar at z = 6.1292

We present deep Keck/MOSFIRE near-infrared spectroscopy of a strong Lyα emitting source at z = 6.1292, HSC J142331.71-001809.1, which was discovered by the SHELLQS program from imaging data of the Subaru Hyper Suprime-Cam (HSC) survey. This source is one of five objects that show narrow (FWHM < 500 km s-1) and prominent (LLyα > 1044 erg s-1) Lyα emission lines at absolute 1450 Å continuum magnitudes of M1450 ~ -22 mag. Its rest-frame Lyα equivalent width (EW) is 370 ± 30 Å. In the 2 hr Keck/MOSFIRE spectrum in Y band, the high-ionization C IV λλ1548,1550 doublet emission line was clearly detected with $\mathrm{FWHM}={120}_{-20}^{+20}$ km s-1 and a total rest-frame EW of ${37}_{-5}^{+6}$ Å. We also report the detection of weak continuum emission, and the tentative detection of O III]λλ1661,1666 in the 4 hr J-band spectrum. Judging from the UV magnitude, line widths, luminosities, and EWs of Lyα and C IV, we suggest that this source is a reionization-era analog of classical type-II AGNs, although there is a possibility that it represents a new population of AGN/galaxy composite objects in the early universe. We compare the properties of J1423-0018 to intermediate-redshift type-II AGNs and C IV emitters seen in z = 6-7 galaxy samples. Further observations of other metal emission lines in the rest-frame UV or optical, along with X-ray follow-up observations of the z = 6-7 narrow-line quasars, are needed for more robust diagnostics and to determine their nature.

Keywords: quasars
Absence of Rapid Line Variations in Consecutive FEROS and NARVAL Spectra of Maia

The comparison of four consecutive high signal-to-noise FEROS spectra of Maia, the fourth brightest member of the Pleiades open cluster, taken over 10 minutes, reveals no real line variations. The analysis of four consecutive I NARVAL profiles of Maia taken over 18 minutes does not show variations either. In particular, the five lines of He I at 4471.48 Å are constant over this timescale in both sets of data. The He I line at 3926.54 Å is very broad and diffuse compared to other photospheric lines of Maia.

Keywords: chemically peculiar stars
Cross-scale Correlations in Imbalanced Solar Wind Turbulence: Parker Solar Probe Observations

Based on Parker Solar Probe observations, this paper investigates the proton temperature, bulk speed, proton-scale magnetic helicity, and spectral index in the parameter space of (P I , σ c ), where P I is the magnetic energy density and σ c is the normalized cross helicity at proton inertial scales. Various correlations between these parameters are discussed and their relations are explored. These correlations indicate the following: (1) the turbulence with a larger P I is characterized by a higher σ c ; (2) a larger P I corresponds to a higher proton temperature, faster bulk speed, and steeper proton-scale magnetic spectrum; (3) a higher σ c accounts for higher proton-scale magnetic helicity. In particular, the P I has the largest correlation coefficient (CC) of 0.85 with proton temperature and has a considerably large CC of 0.70 with a proton-scale spectral index. The σ c has a moderate CC of 0.52 with magnetic helicity in the low β p case (β p < 0.6), where β p is the ratio of plasma to magnetic pressure. The correlation between σ c and P I is considerable with a CC exceeding 0.6 in the low β p case and tends to be negligible when β p approaches 1.5. These findings could be understood by the recently discovered "helicity barrier" effect and underline the importance of the generalized helicity invariant in low β p collisionless plasma for understanding imbalanced solar wind turbulence.

Keywords: solar wind; interplanetary turbulence; solar coronal heating; space plasmas; plasma physics
A Giant Shell of Ionized Gas Discovered near M82 with the Dragonfly Spectral Line Mapper Pathfinder

We present the discovery of a giant cloud of ionized gas in the field of the starbursting galaxy M82. Emission from the cloud is seen in Hα and [N II] λ6583 in data obtained though a small pathfinder instrument used to test the key ideas that will be implemented in the Dragonfly Spectral Line Mapper, an upcoming ultranarrow-bandpass imaging version of the Dragonfly Telephoto Array. The discovered cloud has a shell-like morphology with a linear extent of 0.°8 and is positioned 0.°6 northwest of M82. At the heliocentric distance of the M81 group, the cloud's longest angular extent corresponds to 55 kpc and its projected distance from the nucleus of M82 is 40 kpc. The cloud has an average Hα surface brightness of 2 × 10-18 $\mathrm{erg}\,{\mathrm{cm}}^{-2}\,{{\rm{s}}}^{-1}\,{\mathrm{arcsec}}^{-2}$ . The [N II] λ6583/Hα line ratio varies from [N II]/Hα ~ 0.2 to [N II]/Hα ~ 1.0 across the cloud, with higher values found in its eastern end. Follow-up spectra obtained with Keck LRIS confirm the existence of the cloud and yield line ratios of [N II] λ6583/Hα = 0.340 ± 0.003 and [S II] λλ6716, 6731/Hα = 0.64 ± 0.03 in the cloud. This giant cloud of material could be lifted from M82 by tidal interactions or by its powerful starburst. Alternatively, it may be gas infalling from the cosmic web, potentially precipitated by the superwinds of M82. Deeper data are needed to test these ideas further. The upcoming Dragonfly Spectral Line Mapper will have 120 lenses, 40× more than in the pathfinder instrument used to obtain the data presented here.

Keywords: circumgalactic medium; galaxy evolution; intergalactic medium; intergalactic gas; intergalactic clouds
Microlensing Analysis for the Gravitational Lens Systems SDSS0924+0219, Q1355-2257, and SDSS1029+2623

We use spectroscopic observations of the gravitationally lensed systems SDSS0924+0219(BC), Q1355-2257(AB), and SDSS1029+2623(BC) to analyze microlensing and dust extinction in the observed components. We detect chromatic microlensing effects in the continuum and microlensing in the broad emission line profiles of the systems SDSS0924+0219(BC) and Q1355-2257(AB). Using magnification maps to simulate microlensing and modeling the emitting region as a Gaussian intensity profile with size rs ∝ λp, we obtain the probability density functions for a logarithmic size prior to ${\lambda }_{\mathrm{rest} \mbox{-} \mathrm{frame}}=3533\,\mathring{\rm A} $ . In the case of SDSS0924+0219, we obtain ${r}_{s}={4}_{-2}^{+3}\,\sqrt{M/{M}_{\odot }}$ lt-d (at 1σ), which is larger than the range of other estimates, and p = 0.8 ± 0.2 (at 1σ), which is smaller than predicted by the thin disk theory, but still in agreement with previous results. In the case of Q1355-2257 we obtain (at 1σ) ${r}_{s}={3.6}_{-1.6}^{+3.0}\,\sqrt{M/{M}_{\odot }}$ lt-d, which is also larger than the theoretical prediction, and p = 2.0 ± 0.7, which is in agreement with the theory within errors. SDSS1029+2326 spectra show evidence of extinction, probably produced by a galaxy in the vicinity of image C. Fitting an extinction curve to the data we estimate ΔE ∼ 0.2 in agreement with previous results. We found no evidence of microlensing for this system.

Keywords: strong gravitational lensing; quasar microlensing; quasars
Near-infrared Flux Distribution of Sgr A* from 2005-2022: Evidence for an Enhanced Accretion Episode in 2019

Sgr A* is the variable electromagnetic source associated with accretion onto the Galactic center supermassive black hole. While the near-infrared (NIR) variability of Sgr A* was shown to be consistent over two decades, unprecedented activity in 2019 challenges existing statistical models. We investigate the origin of this activity by recalibrating and reanalyzing all of our Keck Observatory Sgr A* imaging observations from 2005-2022. We present light curves from 69 observation epochs using the NIRC2 imager at 2.12 μm with laser-guide star adaptive optics. These observations reveal that the mean luminosity of Sgr A* increased by a factor of ~3 in 2019, and the 2019 light curves had higher variance than in all time periods we examined. We find that the 2020-2022 flux distribution is statistically consistent with the historical sample and model predictions, but with fewer bright measurements above 0.6 mJy at the ~2σ level. Since 2019, we have observed a maximum K s (2.2 μm) flux of 0.9 mJy, compared to the highest pre-2019 flux of 2.0 mJy and highest 2019 flux of 5.6 mJy. Our results suggest that the 2019 activity was caused by a temporary accretion increase onto Sgr A*, possibly due to delayed accretion of tidally stripped gas from the gaseous object G2 in 2014. We also examine faint Sgr A* fluxes over a long time baseline to search for a quasi-steady quiescent state. We find that Sgr A* displays flux variations over a factor of ~500, with no evidence for a quiescent state in the NIR.

Keywords: black hole physics; accretion; galactic center; high angular resolution
SDSS-IV MaNGA: The Nature of an Off-galaxy Hα Blob—A Multiwavelength View of Offset Cooling in a Merging Galaxy Group

Galaxies in dense environments, such as groups and clusters, experience various processes by which galaxies gain and lose gas. Using data from the SDSS-IV MaNGA survey, we previously reported the discovery of a giant (6—8 kpc in diameter) Hα blob, Totoro, about 8 kpc away from a pair of galaxies (Satsuki and Mei) residing in a galaxy group that is experiencing a group-group merger. Here, we combine interferometric 12CO(1-0) molecular gas data, new wide-field Hα, u-band data, and published X-ray data to determine the origin of the blob. Several scenarios are discussed to account for its multiwavelength properties, including (1) Hα gas being stripped from the galaxy Satsuki by ram pressure, (2) a separated low-surface-brightness galaxy, (3) gas being ejected or ionized by an active galactic nucleus (AGN), and (4) a cooling intragroup medium (IGM). Scenarios (1) and (2) are less favored by the present data. Scenario (3) is also less likely as there is no evidence for an active ongoing AGN in the host galaxy. We find that the CO (cold) and Hα (warm) gas coexist with X-ray (hot) structures; moreover, the derived cooling time is within the regime where molecular and Hα gas are expected. The coexistence of gas with different temperatures also agrees with that of cooling gas in other systems. Our multiwavelength results strongly suggest that the CO and Hα gas are the product of cooling from the IGM at its current location, i.e., cooling has occurred, and may be ongoing, well outside the host-galaxy core.

Keywords: galaxy groups; galaxy interactions; cooling flows; active galactic nuclei
Radio Emission from UV Cet: Auroral Emission from a Stellar Magnetosphere

The archetypical flare star UV Cet was observed by MeerKAT on 2021 October 5-6. A large radio outburst with a duration of ~2 hr was observed between 886 and 1682 MHz, with a time resolution of 8 s and a frequency resolution of 0.84 MHz, enabling sensitive dynamic spectra to be formed. The emission is characterized by three peaks containing a multitude of broadband arcs or partial arcs in the time-frequency domain. In general, the arcs are highly right-hand circularly polarized. At the end of the third peak, brief bursts occur that are significantly elliptically polarized. We present a simple model that appears to be broadly consistent with the characteristics of the radio emission from UV Cet. Briefly, the stellar magnetic field is modeled as a dipole aligned with the rotational axis of the star. The radio emission mechanism is assumed to be due to the cyclotron maser instability, where x-mode radiation near the electron gyrofrequency is amplified. While the elliptically polarized bursts may be intrinsic to the source, rather stringent limits are imposed on the plasma density in the source and along the propagation path. We suggest that the elliptically polarized radiation may instead be the result of reflection on an overdense plasma structure at some distance from the source. The radio emission from UV Cet shares both stellar and planetary attributes.

Keywords: flare stars; uv ceti stars; radio continuum emission; magnetospheric radio emissions; stellar magnetic fields; aurorae