adsabs/SciX_UAT_keywords huggingface dataset:
Effect of Feedback of Massive Stars in the Fragmentation, Distribution, and Kinematics of the Gas in Two Star-forming Regions in the Carina Nebula

We present ALMA high spatial resolution observations toward two star-forming regions located in one of the most extreme zones of star formation in the Galaxy, the Carina Nebula. One region is located at the center of the nebula and is severally affected by the stellar feedback from high-mass stars, while the other region is located farther south and is less disturbed by the massive-star clusters. We found that the region at the center of the nebula is forming less but more massive cores than the region located in the south, suggesting that the level of stellar feedback effectively influences the fragmentation process in clumps. Lines such as HCN, HCO+, and SiO show abundant and complex gas distributions in both regions, confirming the presence of ionization and shock fronts. Jeans analysis suggests that the observed core masses in the region less affected by the massive stars are consistent with thermal fragmentation, but turbulent Jeans fragmentation might explain the high masses of the cores identified in the region in the center of Carina. Consistently, two different analyses in the HCO+ line provided evidence for a higher level of turbulence in the gas more affected by the stellar feedback. The gas column density probability functions, N-pdf's, show lognormal shapes with clear transitions to power-law regimes. We observed a wider N-pdf in the region at the center of the nebula, which provides further evidence for a higher level of turbulence in the material with a higher level of massive stellar feedback.

Keywords: star forming regions; interstellar medium; interstellar molecules; interstellar radiation field; nebulae; interstellar clouds; h ii regions; dense interstellar clouds
The Ubiquity of AGN Winds in Seyfert 1 Galaxies at Low Redshift

The optical spectra of 3896 Seyfert 1 (Sy1) galaxies detected with WISE at z < 0.4 were analyzed for evidence of outflows. In 37% of the Sy1s in our sample, the outflows appear as broad, blue-shifted, spectrally resolved components of the [O III]λ5007 Å emission line, with a mean maximum velocity Vmax ∼ 1014 km s-1 that is consistent with AGN winds. For each Sy1, we deduced the black hole (BH) mass, bolometric luminosity, Eddington ratio, and power-law index of the continuum, which we compared with the star formation rate (SFR) and host morphology. Having separated our sample in two spectroscopic subgroups—Sy1s with only broad Balmer lines (Sy1B) and those with both narrow and broad (Sy1N) lines—and distinguishing those that show as outflow (Sy1Bw and Sy1Nw), we report the following differences: (1) the BH mass is systematically higher and the power-law steeper in the Sy1B-Sy1Bw than in the Sy1N-Sy1Nw; (2) Vmax is higher in the Sy1Bw than in the Sy1Nw, correlated in both groups with the BH mass and bolometric luminosity; (3) the Eddington ratio and SFR are higher in the Sy1 with outflows; and (4) the specific star formation rates (sSFRs) of the Sy1s are normal for their morphology and mass, typical of early-type spiral galaxies in the green valley, far from the quenched regime. From these results, we conclude that AGN winds in Sy1s are triggered by higher accretion rates and probably radiatively launched, and there is no clear evidence of an effect on the star formation.

Keywords: active galaxies; agn host galaxies; active galactic nuclei; galaxies
Inferring the CO2 Abundance in Comet 45P/Honda-Mrkos-Pajdušáková from [O I] Observations: Implications for the Source of Icy Grains in Cometary Comae

The study of cometary composition is important for understanding our solar system's early evolutionary processes. Carbon dioxide (CO2) is a common hypervolatile in comets that can drive activity but is more difficult to study than other hypervolatiles owing to severe telluric absorption. CO2 can only be directly observed from space-borne assets. Therefore, a proxy is needed to measure CO2 abundances in comets using ground-based observations. The flux ratio of the [O I] λ5577 line to the sum of the [O I] λ6300 and [O I] λ6364 lines (hereafter referred to as the [O I] line ratio) has, with some success, been used in the past as such a proxy. We present an [O I] line ratio analysis of comet 45P/Honda-Mrkos-Pajdušáková (HMP), using data obtained with the Tull Coudé Spectrograph on the 2.7 m Harlan J. Smith Telescope at McDonald Observatory, taken from UT 2017 February 21–23, when the comet was at heliocentric distances of 1.12–1.15 au. HMP is a hyperactive Jupiter-family comet (JFC). Icy grains driven out by CO2 sublimation have been proposed as a driver of hyperactivity, but the CO2 abundance of HMP has not been measured. From our [O I] line ratio measurements, we find a CO2/H2O ratio for HMP of 22.9% ± 1.4%. We compare the CO2/H2O ratios to the active fractions of the nine comets (including HMP) in the literature that have data for both values. We find no correlation. These findings imply that CO2 sublimation driving out icy grains is not the only factor influencing active fractions for cometary nuclei.

Keywords: comets; comae; carbon dioxide; comet volatiles; short period comets
Mechanical Modification of Chondrule Fine-grained Rims by Dusty Nebular Shocks

The mechanical processes that convert an initially fluffy chondrule fine-grained rim (FGR) into a more compact structure remain poorly characterized. Given the presence of shocks in protoplanetary disks, we use numerical simulations to test the hypothesis that dust-laden shocks in the solar nebula contributed to FGR modification. We use the iSALE2D shock physics code to model the collision of dusty nebular shock fronts (which we term "dust clouds") into chondrule surfaces that host a porous FGR. In our simulations, dust particles are modeled as dunite disks. The dust radii follow the Mathis-Rumpl-Nordsieck distribution of interstellar grains. Chondrules are modeled as rectangular dunite slabs. We vary the impact speed v imp, the fractional abundance f cloud of dust grains in the impacting shock, and the fractional abundance f FGR of dust grains in the pre-existing FGR. We thus compute dust temperatures and pressures resulting from the collisions, as well as the net mass accretion of dust by the FGRs. Dust temperatures increase upon impact, depending on the kinetic energy of the dust cloud and on f FGR. Dust rims with a higher f FGR heat up more than those with a lower f FGR, with possibly important implications for the composition and structure of FGRs. Maximum impact pressures increase with f cloud. Fine-grained rims can experience mass gain from the impacting cloud, but in some instances, mass is lost from the rim. We find qualitative similarities in the topography of the FGR-chondrule interface between our simulations and petrographic analyses of the Paris CM chondrite by other authors.

Keywords: meteorites; chondrules; chondrites; shocks
The MUSE Ultra Deep Field (MUDF). III. Hubble Space Telescope WFC3 Grism Spectroscopy and Imaging

We present extremely deep Hubble Space Telescope (HST) Wide Field Camera 3 (WFC3) observations of the MUSE Ultra Deep Field. This unique region of the sky contains two quasars at z ≈ 3.22 that are separated by only ~500 kpc, providing a stereoscopic view of gas and galaxies in emission and absorption across ~10 billion years of cosmic time. We have obtained 90 orbits of HST WFC3 G141 near-infrared grism spectroscopy of this field in a single pointing, as well as 142 hr of optical spectroscopy with the Very Large Telescope Multi Unit Spectroscopic Explorer (MUSE). The WFC3 (F140W, F125W, and F336W) and archival WFPC2 (F702W and F450W) imaging provides five-filter photometry that we use to detect 3375 sources between z ≈ 0-6, including 1536 objects in a deep central pointing with both spectroscopic and photometric coverage. The F140W and F336W mosaics reach exceptional depths of m AB ≈ 28 and 29, respectively, providing near-infrared and rest-frame ultraviolet information for 1580 sources, and we reach 5σ continuum detections for objects as faint as m AB ≈ 27 in the grism spectra. The extensive wavelength coverage of MUSE and WFC3 allows us to measure spectroscopic redshifts for 419 sources, down to galaxy stellar masses of log(M/M ⊙) ≈7 at z ≈ 1-2. In this publication, we provide the calibrated HST data and source catalogs as High Level Science Products for use by the community, which includes photometry, morphology, and redshift measurements that enable a variety of studies aimed at advancing our models of galaxy formation and evolution in different environments.

Keywords: astronomical techniques; observational cosmology; high-redshift galaxies; galaxy photometry; galaxy abundances; galaxy evolution
The Polarized Image of a Synchrotron-emitting Ring of Gas Orbiting a Black Hole

Synchrotron radiation from hot gas near a black hole results in a polarized image. The image polarization is determined by effects including the orientation of the magnetic field in the emitting region, relativistic motion of the gas, strong gravitational lensing by the black hole, and parallel transport in the curved spacetime. We explore these effects using a simple model of an axisymmetric, equatorial accretion disk around a Schwarzschild black hole. By using an approximate expression for the null geodesics derived by Beloborodov and conservation of the Walker-Penrose constant, we provide analytic estimates for the image polarization. We test this model using currently favored general relativistic magnetohydrodynamic simulations of M87*, using ring parameters given by the simulations. For a subset of these with modest Faraday effects, we show that the ring model broadly reproduces the polarimetric image morphology. Our model also predicts the polarization evolution for compact flaring regions, such as those observed from Sgr A* with GRAVITY. With suitably chosen parameters, our simple model can reproduce the EVPA pattern and relative polarized intensity in Event Horizon Telescope images of M87*. Under the physically motivated assumption that the magnetic field trails the fluid velocity, this comparison is consistent with the clockwise rotation inferred from total intensity images.

Keywords: accretion; black holes; polarimetry; magnetic fields
How Solar Soft X-Ray Irradiance Is Affected by the Size of Field of View

Soft X-ray images of the Sun obtained with multiple broadband filters provide a simple and useful method to calculate averaged coronal temperature and emission measure, from which we can further calculate solar X-ray irradiance in physical units, e.g., watts per square meter. However, X-ray telescopes are often designed for pursuing high spatial resolution, and thus the field of view (FOV) of full-Sun images is often limited over the limb, extending to only ~1.3 R ⊙. This indicates that the irradiance obtained from the limited FOV may underestimate the true full-Sun irradiance by failing to count the contribution from outside the FOV. This work uses Hinode/X-Ray Telescope (XRT) coronal images observed up to 1.7 R ⊙ to investigate the fraction of irradiance excluded from the FOVs limited in size. The analysis indicates that the irradiance obtained within 1.1 R ⊙, which is used for XRT irradiance study, excludes ~3.5%/~7% of irradiance relative to the value within 1.2/1.7 R ⊙, respectively, for the active corona observed in 2022 July. In contrast, the excluded fraction increases to ~7%/~13%, respectively, for the minimum corona observed in 2009 August. To further investigate the dependence of exclusion fraction on the Sun's activity level, we process mission long Yohkoh/Soft X-ray Telescope full-Sun images to compare the irradiance within 1.1 and 0.9 R ⊙ with that obtained from the maximum FOV of 1.2 R ⊙. We confirm that the exclusion fraction is the largest in the period around solar minimum. We also find that the average value of exclusion fraction is slightly but measurably larger in the rising phase than the declining phase of the solar cycle.

Keywords: solar corona; solar cycle
On the Binary Neutron Star Post-merger Magnetar Origin of XRT 210423

XRT 201423 is an X-ray transient with a nearly flat plateau lasting 4.1 ks followed by a steep decay. This feature indicates that it might come from a magnetar formed through a binary neutron star (BNS) merger, similar to CDF-S XT2 and as predicted as a type of electromagnetic counterpart of BNS mergers. We test the compliance of the data with this model and use the observed duration and flux of the X-ray signal as well as upper limits of optical emission to pose constraints on the parameters of the underlying putative magnetar. Both the free zone and trapped zone geometric configurations are considered. We find that the data are generally consistent with such a model. The surface dipolar magnetic field and the ellipticity of the magnetar should satisfy Bp < 7 × 1014G (Bp < 4.9 × 1014G) and ϵ < 1.5 × 10-3 (ϵ < 1.1 × 10-3) under free zone (trapped zone) configurations, respectively. An upper limit on the distance (e.g., z < 0.55 with ηx = 10-4 or z < 3.5 with ηx = 10-2) can be derived from the X-ray data, which depends on the X-ray dissipation efficiency ηx of the spin-down luminosity. The nondetection of an optical counterpart places a conservative lower limit on the distance of the source, i.e., z > 0.045 regardless of the geometric configuration.

Keywords: x-ray transient sources; magnetars
Supernova-driven Turbulent Metal Mixing in High-redshift Galactic Disks: Metallicity Fluctuations in the Interstellar Medium and its Imprints on Metal-poor Stars in the Milky Way

The extent to which turbulence mixes gas in the face of recurrent infusions of fresh metals by supernovae (SN) could help provide important constraints on the local star formation conditions. This includes predictions of the metallicity dispersion among metal-poor stars, which suggests that the interstellar medium was not very well mixed at these early times. The purpose of this Letter is to help isolate, via a series of numerical experiments, some of the key processes that regulate turbulent mixing of SN elements in galactic disks. We study the gas interactions in small simulated patches of a galaxy disk with the goal of resolving the small-scale mixing effects of metals at parsec scales, which enables us to measure the turbulent diffusion coefficient in various galaxy environments. By investigating the statistics of variations of α elements in these simulations, we are able to derive constraints not only on the allowed range of intrinsic yield variations in SN explosions but also on the star formation history of the Milky Way. We argue that the observed dispersion of [Mg/Fe] in metal-poor halo stars is compatible with the star-forming conditions expected in dwarf satellites or in an early low-star-forming Milky Way progenitor. In particular, metal variations in stars that have not been phase-mixed can be used to infer the star-forming conditions of disrupted dwarf satellites.

Keywords: stellar feedback; galaxy formation; milky way formation; apparent position; metallicity; chemical abundances; interstellar medium
Six-year Static Sky unWISE Coadds

We present and publicly release a set of deep, full-sky Wide-field Infrared Survey Explorer (WISE) coadds built from WISE and NEOWISE images spanning from early 2010 through late 2018. This data release uniformly incorporates six years of WISE and NEOWISE exposures at 3.4 μm (W1) and 4.6 μm (W2). These inertial "unWISE" stacks allow for detection of roughly a billion stars and galaxies fainter than the AllWISE catalogs sensitivity limit. Importantly, our six-year unWISE coadds, in combination with the crowdsource cataloging software, were used to perform deep source detection/deblending for CatWISE2020.

Keywords: infrared astronomy; astronomy data analysis; sky surveys
Magnetically Driven Baryon Winds from Binary Neutron Star Merger Remnants and the Blue Kilonova of 2017 August

The observation of a radioactively powered kilonova associated with the first binary neutron star (BNS) merger detected in gravitational waves proved that these events are ideal sites for the production of heavy r-process elements. However, the physical origin of the ejected material responsible for the early ("blue") and late ("red") components of this kilonova is still debated. Here, we investigate the possibility that the early/blue kilonova originated from the magnetically driven baryon wind launched after merger by the metastable neutron star remnant. Exploiting a magnetized BNS merger simulation with over 250 ms of post-merger evolution, we can follow for the first time the full mass-ejection process up to its final decline. We find that the baryon wind carries ≃0.010-0.028 M⊙ of unbound material, proving that the high mass estimated for the blue kilonova can be achieved. We also find expansion velocities of up to ∼0.2c, consistent with the lower end of the observational estimates, and we discuss possible effects neglected here that could further increase the final ejecta velocity. Overall, our results show that the magnetically driven baryon wind represents a viable channel to explain the blue kilonova.

Keywords: neutron stars; compact binary stars; magnetohydrodynamical simulations; gamma-ray bursts; gravitational wave sources
Discovery of an Extended γ-Ray Emission around the Supernova Remnant Candidate Associated with PSR J0837-2454

Motivated by the recent discovery of a low-surface-brightness diffuse emission, a supernova remnant (SNR) candidate, surrounding the young pulsar PSR J0837-2454, we carry out a likelihood analysis of the γ-ray data obtained by the Fermi Gamma-ray Space Telescope from 2008 August to 2022 November. Using a 2D Gaussian spatial template, we detect a significant extended γ-ray emission with a 68% containment radius of ~1.°8, which is spatially coincident with the new SNR candidate at the ~12σ confidence level. The spectrum of the extended γ-ray emission, obtained in the energy range of 0.1-500.0 GeV, shows a significant spectral curvature at ~1 GeV, with a log-parabola spectral shape. Several scenarios, such as an SNR, pulsar wind nebula, and pulsar halo, are discussed as the potential origins of the extended γ-ray emission, and our model fitting results are preferred for the SNR scenario.

Keywords: gamma-rays; pulsars; supernova remnants
ODNet: A Convolutional Neural Network for Asteroid Occultation Detection

We propose to design and build an algorithm that will use a convolutional neural network (CNN) and observations from the Unistellar Network to reliably detect asteroid occultations. The Unistellar Network is made of more than 10,000 digital telescopes owned by citizen scientists, and is regularly used to record asteroid occultations. In order to process the increasing amount of observational produced by this network, we need a quick and reliable way to analyze occultations. In an effort to solve this problem, we trained a CNN with artificial images of stars with 20 different types of photometric signals. Inputs to the network consist of two stacks of snippet images of stars, one around the star that is supposed to be occulted and a reference star used for comparison. We need the reference star to distinguish between a true occultation and artifacts introduced by a poor atmospheric condition. Our Occultation Detection Neural Network can analyze three sequences of stars per second with 91% precision and 87% recall. The algorithm is sufficiently fast and robust so we can envision incorporating it on board the eVscopes to deliver real-time results. We conclude that citizen science represents an important opportunity for the future studies and discoveries in the occultations, and that application of artificial intelligence will permit us to to take better advantage of the ever-growing quantity of data to categorize asteroids.

Keywords: asteroid occultation; convolutional neural networks; automated telescopes; optical astronomy
The Slow Heartbeats of an Ultraluminous X-Ray Source in NGC 3621

We report on the results of X-ray observations of 4XMM J111816.0-324910, a transient ultraluminous X-ray source located in the galaxy NGC 3621. This system is characterized by a transient nature and marked variability with a characteristic timescale of ≈3500 s, in contract with other ultraluminous X-ray sources, which in the vast majority show limited intra-observation variability. Such a behavior is very reminiscent of the so-called heartbeats sometimes observed in the Galactic black hole binary GRS 1915+105, where the variability timescale is ∼10-1000 s. We study the spectral and timing properties of this object and find that overall, once the differences in the variability timescales are taken into account, they match quite closely those of both GRS 1915+105 and of a number of objects showing heartbeats in their light curves, including a confirmed neutron star and a supermassive black hole powering an active galactic nucleus. We investigate the nature of the compact object in 4XMM J111816.0-324910 by searching for typical neutron star signatures and by attempting a mass estimate based on different methods and assumptions. Based on the current available data, we are not able to unambiguously determine the nature of the accreting compact object responsible for the observed phenomenology.

Keywords: black holes; neutron stars; accretion; x-ray point sources; compact objects; extragalactic astronomy
Photosynthetic Fluorescence from Earthlike Planets around Sunlike and Cool Stars

Remote sensing of the Earth has demonstrated that photosynthesis is traceable as the vegetation red edge (VRE), which is a steep rise in the reflection spectrum of vegetation, and as solar-induced fluorescence. This study examines the detectability of biological fluorescence from two types of photosynthetic pigments, chlorophylls (Chls) and bacteriochlorophylls (BChls), on Earthlike planets with oxygen-rich/poor and anoxic atmospheres around the Sun and M dwarfs. Atmospheric absorption, such as H2O, CH4, O2, and O3, and the VRE obscure the fluorescence emissions from Chls and BChls. We find that the BChl-based fluorescence for wavelengths of 1000-1100 nm, assuming the spectrum of BChl b-bearing purple bacteria, could provide a suitable biosignature, but only in the absence of water cloud coverage or other strong absorbers near 1000 nm. The Chl fluorescence is weaker for several reasons, e.g., spectral blending with the VRE. The apparent reflectance excess is greatly increased in both the Chl and BChl cases around TRAPPIST-1, due to the fluorescence and stellar absorption lines. This could be a promising feature for detecting the fluorescence around ultracool red dwarfs using follow-up ground-based observations at high spectral resolution; however, this would require a long time around Sunlike stars, even for a LUVOIR-like space mission. Moreover, the simultaneous detection of fluorescence and the VRE is the key to identifying traces of photosynthesis, because absorption, reflectance, and fluorescence are physically connected. For further validation of the fluorescence detection, the nonlinear response of biological fluorescence as a function of light intensity could be considered.

Keywords: astrobiology; exoplanet surfaces; biosignatures