adsabs/SciX_UAT_keywords huggingface dataset:
The CAMELS Project: Cosmology and Astrophysics with Machine-learning Simulations

We present the Cosmology and Astrophysics with MachinE Learning Simulations (CAMELS) project. CAMELS is a suite of 4233 cosmological simulations of ${\left(25{h}^{-1}\mathrm{Mpc}\right)}^{3}$ volume each: 2184 state-of-the-art (magneto)hydrodynamic simulations run with the AREPO and GIZMO codes, employing the same baryonic subgrid physics as the IllustrisTNG and SIMBA simulations, and 2049 N-body simulations. The goal of the CAMELS project is to provide theory predictions for different observables as a function of cosmology and astrophysics, and it is the largest suite of cosmological (magneto)hydrodynamic simulations designed to train machine-learning algorithms. CAMELS contains thousands of different cosmological and astrophysical models by way of varying Ωm, σ8, and four parameters controlling stellar and active galactic nucleus feedback, following the evolution of more than 100 billion particles and fluid elements over a combined volume of ${(400{h}^{-1}\mathrm{Mpc})}^{3}$ . We describe the simulations in detail and characterize the large range of conditions represented in terms of the matter power spectrum, cosmic star formation rate density, galaxy stellar mass function, halo baryon fractions, and several galaxy scaling relations. We show that the IllustrisTNG and SIMBA suites produce roughly similar distributions of galaxy properties over the full parameter space but significantly different halo baryon fractions and baryonic effects on the matter power spectrum. This emphasizes the need for marginalizing over baryonic effects to extract the maximum amount of information from cosmological surveys. We illustrate the unique potential of CAMELS using several machine-learning applications, including nonlinear interpolation, parameter estimation, symbolic regression, data generation with Generative Adversarial Networks, dimensionality reduction, and anomaly detection.

Keywords: cosmology; cosmological parameters from large-scale structure; galaxy formation; astrostatistics
A Novel Model for the MeV Emission Line in GRB 221009A

Gamma-ray bursts (GRBs) have long been considered potential sources of ultrahigh-energy cosmic rays (UHECRs; with energy ≳1018 eV). In this work, we propose a novel model generating MeV emission lines in GRBs, which can constrain the properties of heavy nuclei that potentially exist in GRB jets. Specifically, we find that relativistic hydrogen-like high-atomic-number ions originating from the β decay of unstable nuclei and/or the recombination entrained in the GRB jet can generate narrow MeV emission lines through the de-excitation of excited electrons. This model can successfully explain the MeV emission line observed in the most luminous GRB ever recorded, GRB 221009A, with suitable parameters including a Lorentz factor γ ∼ 820–1700 and a total mass of heavy nuclei M tot ∼ 1023–1026 g. Especially, the emission line broadening can be reasonably attributed to both the expansion of the jet shell and the thermal motion of nuclei, naturally resulting in a narrow width (σ line/E line ≲ 0.2) consistent with the observation. Furthermore, we predict that different GRBs can exhibit lines in different bands with various evolving behaviors, which might be confirmed with further observations. Finally, our model provides indirect evidence that GRBs may be one of the sources of UHECRs.

Keywords: gamma-ray bursts; gamma-ray lines; particle astrophysics; cosmic ray sources; high-energy cosmic radiation
Photometric Objects around Cosmic Webs (PAC) Delineated in a Spectroscopic Survey. I. Methods

We provide a method for estimating the projected density distribution ${\bar{n}}_{2}{w}_{p}({r}_{p})$ of photometric objects around spectroscopic objects in a spectroscopic survey. This quantity describes the distribution of photometric sources with certain physical properties (e.g., luminosity, mass, and color) around cosmic webs (PAC) traced by the spectroscopic objects. The method can make full use of current and future deep and wide photometric surveys to explore the formation of galaxies up to medium redshift (z s < 2) 3 3 Throughout the paper, we use z s for redshift, z for the z-band magnitude, z p for the photometric redshift. with the aid of cosmological spectroscopic surveys that sample only a fairly limited species of objects (e.g., emission line galaxies). As an example, we apply the PAC method to the CMASS spectroscopic and HSC-SSP PDR2 photometric samples to explore the distribution of galaxies for a wide range of stellar masses from 109.0 to 1012.0 M ⊙ around massive galaxies at z s ≈ 0.6. Using the abundance-matching method, we model ${\bar{n}}_{2}{w}_{p}({r}_{p})$ in N-body simulation using Markov chain Monte Carlo sampling, and we accurately measure the stellar-halo mass relation and stellar mass function for the whole mass range. We can also measure the conditional stellar mass function of satellites for central galaxies of different mass. The PAC method has many potential applications for studying the evolution of galaxies.

Keywords: galaxy formation; observational cosmology; galaxy dark matter halos
Wayne State University's Dan Zowada Memorial Observatory: Characterization and Pipeline of a 0.5 m Robotic Telescope

Wayne State University's Dan Zowada Memorial Observatory is a fully robotic 0.5 m telescope and imaging system located under the dark skies of New Mexico. The observatory is particularly suited to time domain astronomy: the observation of variable objects, such as tidal disruption events, supernovae, and active galactic nuclei. We have developed a software suite for image reduction, alignment and stacking, and calculation of absolute photometry in the Sloan filters used at the telescope. Our pipeline also performs image subtraction to enable photometry of objects embedded in bright backgrounds such as galaxies. The 5σ detection limit of the Zowada Observatory for integration of 16 × 90 s exposures is 19.0 mag in g-band, 18.1 mag in r-band, 17.9 mag in i-band, and 16.6 mag in z-band. For a 3σ detection limit, measurements may be performed with greater uncertainties as deep as 19.9, 19.1. 18.9 and 17.5 mag in griz bands, respectively.

Keywords: burkert profile; astronomy software; calibration; ccd photometry; light curves; observatories; optical observatories; sloan photometry
Multiple Stellar Populations along the Red Horizontal Branch and Red Clump of Globular Clusters

We exploit multiband Hubble Space Telescope photometry to investigate multiple populations (MPs) along the red horizontal branches (HBs) and red clumps of 14 metal-rich globular clusters (GCs), including 12 Milky Way GCs and the Magellanic Cloud GCs NGC 1978 and NGC 416. Based on appropriate two-color diagrams, we find that the fraction of first-generation (1G) stars in Galactic GCs correlates with cluster mass, confirming previous results based on red-giant branch (RGB) stars. Magellanic Cloud GCs show higher fractions of 1G stars than Galactic GCs with similar masses, thus suggesting that the environment affects the MP phenomenon. We compared and combined our population fractions based on the HB with previous estimates from the MS and RGB, and we used ground-based UBVI photometry (available for NGC 104, NGC 5927, NGC 6366, and NGC 6838) to extend the investigation over a wide field of view. All studied GCs are consistent with flat distributions of 1G and second-generation (2G) stars within ∼1' from the cluster center except NGC 416, where the 2G is more centrally concentrated. 2G stars of NGC 104 and NGC 5927 are more centrally concentrated than the 1G stars, whereas the distribution is flat for NGC 6366 and NGC 6838. We discover that most of the analyzed GCs exhibit extended sequences of 1G stars along the red HB, not consistent with a simple population. The comparison between appropriate synthetic and observed CMDs reveals that these extended distributions are consistent with either star-to-star variation in helium or with an internal metallicity spread, recalling the inhomogeneity of 1G stars along the chromosome maps.

Keywords: globular star clusters; population ii stars; chemical abundances; hst photometry; magellanic clouds
Discovery of Beryllium in White Dwarfs Polluted by Planetesimal Accretion

The element beryllium is detected for the first time in white dwarf stars. This discovery in the spectra of two helium-atmosphere white dwarfs was made possible only because of the remarkable overabundance of Be relative to all other elements, heavier than He, observed in these stars. The measured Be abundances, relative to chondritic, are by far the largest ever seen in any astronomical object. We anticipate that the Be in these accreted planetary bodies was produced by spallation of one or more of O, C, and N in a region of high fluence of particles of MeV or greater energy.

Keywords: white dwarf stars; abundance ratios; overabundances; high resolution spectroscopy; stellar spectral lines; stellar accretion; planetesimals; extrasolar rocky planets
Extended Radio AGN at z ∼ 1 in the ORELSE Survey: The Confining Effect of Dense Environments

Recent hydrodynamic simulations and observations of radio jets have shown that the surrounding environment has a large effect on their resulting morphology. To investigate this, we use a sample of 50 Extended Radio Active Galactic Nuclei (ERAGN) detected in the Observations of Redshift Evolution in Large-Scale Environments survey. These sources are all successfully cross-identified to galaxies within a redshift range of 0.55 ≤ z ≤ 1.35, either through spectroscopic redshifts or accurate photometric redshifts. We find that ERAGN are more compact in high-density environments than those in low-density environments at a significance level of 4.5σ. Among a series of internal properties under our scrutiny, only the radio power demonstrates a positive correlation with their spatial extent. After removing the possible radio power effect, the difference of size in low- and high-density environments persists. In the global environment analyses, the majority (86%) of high-density ERAGN reside in the cluster/group environment. In addition, ERAGN in the cluster/group central regions are preferentially compact with a small scatter in size, compared to those in the cluster/group intermediate regions and fields. In conclusion, our data appear to support the interpretation that the dense intracluster gas in the central regions of galaxy clusters plays a major role in confining the spatial extent of radio jets.

Keywords: radio active galactic nuclei; radio galaxies; galaxy clusters; radio jets
The JWST Resolved Stellar Populations Early Release Science Program. III. Photometric Star-Galaxy Separations for NIRCam

We present criteria for separately classifying stars and unresolved background galaxies in photometric catalogs generated with the point-spread function fitting photometry software DOLPHOT from images taken of Draco II, WLM, and M92 with the Near Infrared Camera (NIRCam) on JWST. Photometric quality metrics from DOLPHOT in one or two filters can recover a pure sample of stars. Conversely, colors formed between short-wavelength and long-wavelength filters can be used to effectively identify pure samples of galaxies. Our results highlight that the existing DOLPHOT output parameters can be used to reliably classify stars in our NIRCam data without the need to resort to external tools or more complex heuristics.

Keywords: multi-color photometry; photometry; stellar populations; two-color diagrams; classification; james webb space telescope
FUMES. III. Ultraviolet and Optical Variability of M-dwarf Chromospheres

We obtained ultraviolet and optical spectra for nine M dwarfs across a range of rotation periods to determine whether they showed stochastic intrinsic variability distinguishable from flares. The ultraviolet spectra were observed during the Far Ultraviolet M-dwarf Evolution Survey Hubble Space Telescope program using the Space Telescope Imaging Spectrograph. The optical observations were taken from the Apache Point Observatory 3.5 m telescope using the Dual Imaging Spectrograph and from the Gemini South Observatory using the Gemini Multi-Object Spectrograph. We used the optical spectra to measure multiple chromospheric lines: the Balmer series from Hα to H10 and the Ca II H and K lines. We find that after excising flares, these lines vary on the order of 1%-20% at minute-cadence over the course of an hour. The absolute amplitude of variability was greater for the faster rotating M dwarfs in our sample. Among the five stars for which we measured the weaker Balmer lines, we note a tentative trend that the fractional amplitude of the variability increases for higher-order Balmer lines. We measured the integrated flux of multiple ultraviolet emission features formed in the transition region: the N V, Si IV, and C IV resonance line doublets, and the C II and He II multiplets. The signal-to-noise ratio of the UV data was too low for us to detect nonflare variability at the same scale and time cadence as the optical. We consider multiple mechanisms for the observed stochastic variability and propose both observational and theoretical avenues of investigation to determine the physical causes of intrinsic variability in the chromospheres of M dwarfs.

Keywords: m dwarf stars; stellar activity; stellar rotation
Solar Cycle of Imaging the Global Heliosphere: Interstellar Boundary Explorer (IBEX) Observations from 2009-2019

NASA's Interstellar Boundary Explorer (IBEX) mission has operated in space for a full solar activity cycle (Solar Cycle 24), and IBEX observations have exposed the global three-dimensional structure of the heliosphere and its interaction with the very local interstellar medium for the first time. Here, we extend the prior IBEX observations of energetic neutral atoms (ENAs) by adding a comprehensive analysis of four additional years (2016 through 2019). We document several improvements and rerelease the entire 11 yr, IBEX-Hi data set. The new observations track the continuing expansion of the outer heliosphere's response to the large solar wind pressure increase in late 2014. We find that the intensification of ENAs from the heliosheath continued to expand progressively over time to directions farther from the initial, closest direction to the heliospheric boundaries, ∼20° south of the upwind direction. This expansion extended beyond the south pole in 2018 and the north pole in 2019, demonstrating that the termination shock and heliopause are closer in the south. The heliotail has not yet responded, indicating that the boundaries are significantly farther away in the downwind direction. Finally, the slow solar wind (∼1 keV) ENAs just started to intensify from the closest regions of the IBEX Ribbon. This is about two and a half years after the initial response from heliosheath ENAs and about four and a half years after the increase in solar wind output, both clearly implicating a "secondary ENA" source in the draped interstellar magnetic field, just beyond the heliopause.

Keywords: heliosphere; solar wind; pickup ions; interstellar medium; heliosheath; solar cycle; solar activity; interstellar magnetic fields
Circumgalactic Medium on the Largest Scales: Detecting X-Ray Absorption Lines with Large-area Microcalorimeters

The circumgalactic medium (CGM) plays a crucial role in galaxy evolution as it fuels star formation, retains metals ejected from the galaxies, and hosts gas flows in and out of galaxies. For Milky Way-type and more-massive galaxies, the bulk of the CGM is in hot phases best accessible at X-ray wavelengths. However, our understanding of the CGM remains largely unconstrained due to its tenuous nature. A promising way to probe the CGM is via X-ray absorption studies. Traditional absorption studies utilize bright background quasars, but this method probes the CGM in a pencil beam, and, due to the rarity of bright quasars, the galaxy population available for study is limited. Large-area, high spectral resolution X-ray microcalorimeters offer a new approach to exploring the CGM in emission and absorption. Here, we demonstrate that the cumulative X-ray emission from cosmic X-ray background sources can probe the CGM in absorption. We construct column density maps of major X-ray ions from the Magneticum simulation and build realistic mock images of nine galaxies to explore the detectability of X-ray absorption lines arising from the large-scale CGM. We conclude that the O VII absorption line is detectable around individual massive galaxies at the 3σ-6σ confidence level. For Milky Way-type galaxies, the O VII and O VIII absorption lines are detectable at the ~ 6σ and ~ 3σ levels even beyond the virial radius when coadding data from multiple galaxies. This approach complements emission studies, does not require additional exposures, and will allow for probing the baryon budget and the CGM at the largest scales.

Keywords: circumgalactic medium; disk galaxies; galaxy evolution; high resolution spectroscopy; x-ray astronomy; x-ray observatories; x-ray sources
Recombination-independent Determination of the Sound Horizon and the Hubble Constant from BAO

The Hubble tension and attempts to resolve it by modifying the physics of (or at) recombination motivate finding ways to determine H0 and the sound horizon at the epoch of baryon decoupling rd in ways that rely neither on a recombination model nor on late-time Hubble data. In this work, we investigate what one can learn from the current and future BAO data when treating rd and H0 as independent free parameters. It is well known that baryon acoustic oscillations (BAOs) give exquisite constraints on the product rdH0. We show here that imposing a moderate prior on Ωmh2 breaks the degeneracy between rd and H0. Using the latest BAO data, including the recently released the extended Baryon Oscillation Spectroscopic Survey Data Release 16, along with a Ωmh2 prior based on the Planck best-fit Λ cold dark matter (ΛCDM) model, we find rd = 143.7 ± 2.7 Mpc and H0 = 69.6 ± 1.8 km s-1 Mpc-1. BAO data prefers somewhat lower rd and higher H0 than those inferred from Planck data in a ΛCDM model. We find similar values when combing BAO with the Pantheon supernovae, the Dark Energy Survey Year 1 galaxy weak lensing, Planck or SPTPol cosmic microwave background lensing, and the cosmic chronometer data. We perform a forecast for the Dark Energy Spectroscopic Instrument (DESI) and find that, when aided with a moderate prior on Ωmh2, DESI will measure rd and H0 without assuming a recombination model with an accuracy surpassing the current best estimates from Planck.

Keywords: cosmology; baryon acoustic oscillations; hubble constant; recombination (cosmology)
Near-infrared Polarimetry and H2 Emission toward Massive Young Stars: Discovery of a Bipolar Outflow Associated to S235 e2s3

We present a near-infrared H-band polarimetric study toward the S235 e2s3 protostar, obtained using the POLICAN instrument on the 2.1 m OAGH telescope. The images reveal a bipolar outflow with a total length of about 0.5 pc. The outflow nebulosity presents a high degree of linear polarization (~80%) and reveals a centrosymmetric pattern with the polarization position angles. The polarization characteristics suggest their origin to be single scattering associated with dust in the outflow. Using multiwavelength archival data, we performed spectral energy distribution (SED) fitting based on radiative transfer models of turbulent core accretion theory. The best-fit SED model indicated that the protostar has a mass of 6.8 ± 1.2 M ⊙, with a disk accretion rate of 3.6 ± 1.2 × 10-4 M ⊙ yr-1 and a total bolometric luminosity of 9.63 ± 2.1 × 103 L ⊙. Narrowband H2 (2.12 μm) observations show shocked emission along the bipolar lobes tracing the jet's interaction with the surrounding medium. The estimated H2 luminosity of the outflow is ${2.3}_{-1.3}^{+3.5}\,{L}_{\odot }$ , which matched the known power-law correlation with the source bolometric luminosity, similar to other high-mass outflows. The orientation of the bipolar outflow was found to be parallel to the local magnetic field direction. The overall results assert the fact that the S235 e2s3 source is a massive young star driving a highly collimated bipolar outflow through disk accretion.

Keywords: massive stars; polarimetry; protostars; spectral energy distribution; star formation; stellar jets
Accounting for Selection Bias Using Simulations: A General Method and an Application to Millimeter-wavelength Surveys

We have developed a new Bayesian method to correct the flux densities of astronomical sources. The hybrid method combines a simulated likelihood to model survey selection together with an analytic source-count-based prior. The simulated likelihood captures the effect of complicated selection methods, such as multi-frequency filtering or imposed restrictions on recovered sample properties (e.g., color cuts). Simulations are also able to capture unanticipated sources of uncertainty. In this way, the method enables a broader application of Bayesian techniques. Use of an analytic prior allows variation of assumed source count models without re-simulating the likelihood. We present the method along with a detailed description of an application to real survey data from the Atacama Cosmology Telescope.

Keywords: astronomy data modeling; astronomical techniques; astronomical methods; radio source catalogs; submillimeter astronomy
Detection of Dust Particles Using Faraday Cup Instruments

Faraday cups can measure velocity distribution functions of space plasmas and are frequent instruments on heliophysics missions. A new version of a Faraday cup instrument is in development for the Luna 26 mission and will be used for fast monitoring of the solar wind plasma parameters. The prototype of this instrument is exposed to dust impacts in a velocity range of 0.2-60 km s-1 using an electrostatic dust accelerator. The collected data are used to evaluate the sensitivity and detection efficiency of dust particles on two different surfaces. The results indicate that the sensitivity is sufficient for detection of the interplanetary dust as well as for the registration of the dust lifted from the lunar surface. A simple modification of the FC electronics would increase the detection efficiency by an order of magnitude.

Keywords: interplanetary dust; interstellar dust; solid matter physics
The Structure of Magnetic Fields in Spiral Galaxies: A Radio and Far-infrared Polarimetric Analysis

We propose and apply a method to quantify the morphology of the large-scale ordered magnetic fields (B-fields) in galaxies. This method is adapted from the analysis of Event Horizon Telescope polarization data. We compute a linear decomposition of the azimuthal modes of the polarization field in radial galactocentric bins. We apply this approach to five low-inclination spiral galaxies with both far-infrared (FIR: 154 μm) dust polarimetric observations taken from the Survey of Extragalactic Magnetism with SOFIA (SALSA) and radio (6 cm) synchrotron polarization observations. We find that the main contribution to the B-field structure of these spiral galaxies comes from the m = 2 and m = 0 modes at FIR wavelengths and the m = 2 mode at radio wavelengths. The m = 2 mode has a spiral structure and is directly related to the magnetic pitch angle, while m = 0 has a constant B-field orientation. The FIR data tend to have a higher relative contribution from other modes than the radio data. The extreme case is NGC 6946: all modes contribute similarly in the FIR, while m = 2 still dominates in the radio. The average magnetic pitch angle in the FIR data is smaller and has greater angular dispersion than in the radio, indicating that the B-fields in the disk midplane traced by FIR dust polarization are more tightly wound and more chaotic than the B-field structure in the radio, which probes a larger volume. We argue that our approach is more flexible and model independent than standard techniques, while still producing consistent results where directly comparable.

Keywords: polarimetry; spiral galaxies; extragalactic magnetic fields; radio observatories; far infrared astronomy; spiral arms