adsabs/SciX_UAT_keywords huggingface dataset:
LOFAR Observations of a Jet-driven Piston Shock in the Low Solar Corona

The Sun produces highly dynamic and eruptive events that can drive shocks through the corona. These shocks can accelerate electrons, which result in plasma emission in the form of a type II radio burst. Despite the large number of type II radio burst observations, the precise origin of coronal shocks is still subject to investigation. Here, we present a well-observed solar eruptive event that occurred on 2015 October 16, focusing on a jet observed in the extreme ultraviolet by the Atmospheric Imaging Assembly (SDO/AIA), a streamer observed in white light by the Large Angle and Spectrometric Coronagraph (SOHO/LASCO), and a metric type II radio burst observed by the LOw Frequency Array (LOFAR). LOFAR interferometrically imaged the fundamental and harmonic sources of a type II radio burst and revealed that the sources did not appear to be cospatial, as would be expected from the plasma emission mechanism. We correct for the separation between the fundamental and harmonic using a model that accounts for scattering of radio waves by electron density fluctuations in a turbulent plasma. This allows us to show the type II radio sources were located ∼0.5R⊙ above the jet and propagated at a speed of ∼1000 km s-1, which was significantly faster than the jet speed of ∼200 km s-1. This suggests that the type II burst was generated by a piston shock driven by the jet in the low corona.

Keywords: active solar corona; solar radio emission; shocks; radio bursts; plasma jets; solar flares; solar coronal streamers; solar extreme ultraviolet emission
Star Formation Suppression by Tidal Removal of Cold Molecular Gas from an Intermediate-redshift Massive Post-starburst Galaxy

Observations and simulations have demonstrated that star formation in galaxies must be actively suppressed to prevent the formation of overly massive galaxies. Galactic outflows driven by stellar feedback or supermassive black hole accretion are often invoked to regulate the amount of cold molecular gas available for future star formation but may not be the only relevant quenching processes in all galaxies. We present the discovery of vast molecular tidal features extending up to 64 kpc outside of a massive z = 0.646 post-starburst galaxy that recently concluded its primary star-forming episode. The tidal tails contain (1.2 ± 0.1) × 1010 M ⊙ of molecular gas, 47% ± 5% of the total cold gas reservoir of the system. Both the scale and magnitude of the molecular tidal features are unprecedented compared to all known nearby or high-redshift merging systems. We infer that the cold gas was stripped from the host galaxies during the merger, which is most likely responsible for triggering the initial burst phase and the subsequent suppression of star formation. While only a single example, this result shows that galaxy mergers can regulate the cold gas contents in distant galaxies by directly removing a large fraction of the molecular gas fuel, and plausibly suppress star formation directly, a qualitatively different physical mechanism than feedback-driven outflows.

Keywords: galaxy mergers; tidal tails; galaxy quenching; molecular gas
Host-star Properties of Hot, Warm, and Cold Jupiters in the Solar Neighborhood from Gaia Data Release 3: Clues to Formation Pathways

Giant planets exhibit diverse orbital properties, hinting at their distinct formation and dynamic histories. In this paper, using Gaia Data Release 3 (DR3), we investigate if and how the orbital properties of Jupiters are linked to their host star properties, particularly their metallicity and age. We obtain metallicities for main-sequence stars of spectral type F, G, and K, hosting hot, warm, and cold Jupiters with varying eccentricities. We compute the velocity dispersions of the host stars of these three groups using kinematic information from Gaia DR3 and obtain average ages using a velocity dispersion–age relation. We find that the host stars of hot Jupiters are relatively metal rich ([Fe/H] = 0.18 ± 0.13) and young (median age of 3.97 ± 0.51 Gyr) compared to the host stars of cold Jupiters in nearly circular orbits, which are relatively metal poor (0.03 ± 0.18) and older (median age of 6.07 ± 0.79 Gyr). The host stars of cold Jupiters in high-eccentricity orbits, on the other hand, show metallicities similar to those of the hosts of hot Jupiters, but are older, on average (median age of 6.25 ± 0.92 Gyr). The similarity in metallicity between the hosts of hot Jupiters and the hosts of cold Jupiters in high-eccentricity orbits supports high-eccentricity migration as the potential origin of hot Jupiters, with the latter serving as the progenitors of hot Jupiters. However, the average age difference between them suggests that the older hot Jupiters may have been engulfed by their host star over timescales ∼ 6 Gyr. This allows us to estimate the value of stellar tidal quality factor, .

Keywords: gaia; hot jupiters; metallicity; exoplanet migration; tidal interaction
Origin and Evolution of Dust-obscured Galaxies in Galaxy Mergers

Dust-obscured galaxies (DOGs), which are observationally characterized as faint in the optical and bright in the infrared, are the final stage of galaxy mergers and are essential objects in the evolution of galaxies and active galactic nuclei (AGNs). However, the relationship between the torus-scale gas dynamics around AGNs and the DOGs' lifetime remains unclear. We obtained the evolution of the spectral energy distributions (SEDs) of a galaxy merger system with AGN feedback from postprocessed pseudo-observations based on an N-body/smoothed particle hydrodynamics (SPH) simulation. We focused on a late-stage merger of two identical galaxies with a supermassive black hole (SMBH) of 108 M ⊙. We found that the infrared luminosity of the system reaches ultra- and hyperluminous infrared galaxy classes (1012 and 1013 L ⊙, respectively). The DOG phase corresponds to a state in which the AGNs are buried in dense gas and dust, with the infrared luminosity exceeding 3.3 × 1012 L ⊙. We also identified subcategories of DOGs, namely bump and power-law DOGs, from the SEDs and their evolution. The bump DOGs tend to evolve to power-law DOGs over several Myrs. We found that contribution from the hot dust around the nucleus in the infrared radiation is essential for identifying the system as a power-law DOG; the gas and dust are distributed nonspherically around the nucleus, therefore, the observed properties of DOGs depend on the viewing angle. In our model, the lifetime of merger-driven DOGs is less than 4 Myr, suggesting that the observed DOG phase is a brief aspect of galaxy mergers.

Keywords: supermassive black holes; galaxy mergers; active galaxies; active galactic nuclei; n-body simulations; hydrodynamical simulations; radiative transfer simulations
What Holes in the Gas Distribution of Nearly Face-on Galaxies Can Tell Us about the Host Disk Parameters: The Case of the NGC 628 Southeast Superbubble

Here we explore the impact of all major factors, such as the nonhomogeneous gas distribution, galactic rotation, and gravity, on the observational appearance of superbubbles in nearly face-on spiral galaxies. The results of our 3D numerical simulations are compared to the observed gas column density distribution in the largest southeast superbubble in the late-type spiral galaxy NGC 628. We make use of the star formation history inside the bubble derived from the resolved stellar population seen in Hubble Space Telescope images to obtain its energy and demonstrate that the results of numerical simulations are in good agreement with the observed gas surface density distribution. We also show that the observed gas column density distribution constrains the gaseous disk scale height and the midplane gas density if the energy input rate can be obtained from observations. This implies that observations of large holes in the interstellar gas distribution and their stellar populations have the potential power to solve the midplane gas density-gaseous disk scale height degeneracy problem in nearly face-on galaxies. The possible role of superbubbles in driving the secondary star formation in galaxies is also briefly discussed.

Keywords: interstellar medium; superbubbles; disk galaxies; stellar feedback
Residual Abundances in GALAH DR3: Implications for Nucleosynthesis and Identification of Unique Stellar Populations

We investigate the [X/Mg] abundances of 16 elements for 82,910 Galactic disk stars from GALAH+ DR3. We fit the median trends of low-Ia and high-Ia populations with a two-process model, which describes stellar abundances in terms of a prompt core-collapse and delayed Type-Ia supernova component. For each sample star, we fit the amplitudes of these two components and compute the residual Δ[X/H] abundances from this two-parameter fit. We find rms residuals ≲0.07 dex for well-measured elements and correlated residuals among some elements (such as Ba, Y, and Zn) that indicate common enrichment sources. From a detailed investigation of stars with large residuals, we infer that roughly 40% of the large deviations are physical and 60% are caused by problematic data such as unflagged binarity, poor wavelength solutions, and poor telluric subtraction. As one example of a population with distinctive abundance patterns, we identify 15 stars that have 0.3-0.6 dex enhancements of Na but normal abundances of other elements from O to Ni and positive average residuals of Cu, Zn, Y, and Ba. We measure the median elemental residuals of 14 open clusters, finding systematic ~0.1-0.4 dex enhancements of O, Ca, K, Y, and Ba and ~0.2 dex depletion of Cu in young clusters. Finally, we present a restricted three-process model where we add an asymptotic giant branch star (AGB) component to better fit Ba and Y. With the addition of the third process, we identify a population of stars, preferentially young, that have much higher AGB enrichment than expected from their SNIa enrichment.

Keywords: chemical abundances; galactic abundances; core-collapse supernovae; type ia supernovae; asymptotic giant branch stars
The Evolution of the Inner Regions of Protoplanetary Disks

We present a study of the evolution of the inner few astronomical units of protoplanetary disks around low-mass stars. We consider nearby stellar groups with ages spanning from 1 to 11 Myr, distributed into four age bins. Combining PANSTARSS photometry with spectral types, we derive the reddening consistently for each star, which we use (1) to measure the excess emission above the photosphere with a new indicator of IR excess and (2) to estimate the mass accretion rate ( $\dot{M}$ ) from the equivalent width of the Hα line. Using the observed decay of $\dot{M}$ as a constraint to fix the initial conditions and the viscosity parameter of viscous evolutionary models, we use approximate Bayesian modeling to infer the dust properties that produce the observed decrease of the IR excess with age, in the range between 4.5 and 24 μm. We calculate an extensive grid of irradiated disk models with a two-layered wall to emulate a curved dust inner edge and obtain the vertical structure consistent with the surface density predicted by viscous evolution. We find that the median dust depletion in the disk upper layers is $\epsilon \sim 3\times {10}^{-3}$ at 1.5 Myr, consistent with previous studies, and it decreases to $\epsilon \sim 3\times {10}^{-4}$ by 7.5 Myr. We include photoevaporation in a simple model of the disk evolution and find that a photoevaporative wind mass-loss rate of $\sim 1\mbox{--}3\times {10}^{-9}\,{M}_{\odot }\,{\mathrm{yr}}^{-1}$ agrees with the decrease of the disk fraction with age reasonably well. The models show the inward evolution of the H2O and CO snowlines.

Keywords: protoplanetary disks; pre-main sequence stars; t tauri stars; stellar accretion disks
High-energy Gamma Rays from Magnetically Arrested Disks in Nearby Radio Galaxies

The origins of the GeV gamma rays from nearby radio galaxies are unknown. Hadronic emission from magnetically arrested disks (MADs) around central black holes is proposed as a possible scenario. Particles are accelerated in a MAD by magnetic reconnection and stochastic turbulence acceleration. We pick out the 15 brightest radio galaxies in the GeV band from The Fourth Catalog of Active Galactic Nuclei Detected by the Fermi Large Area Telescope, Data Release 2 and apply the MAD model. We find that we can explain the data in the GeV bands by the MAD model if the accretion rate is lower than 0.1% of the Eddington rate. For a higher accretion rate, GeV gamma rays are absorbed by two-photon interaction due to copious low-energy photons. If we assume another proposed prescription of the electron-heating rate by magnetic reconnection, the MAD model fails to reproduce the GeV data for the majority of our sample. This indicates that the electron-heating rate is crucial. We also apply the MAD model to Sagittarius A* (Sgr A*) and find that GeV gamma rays observed at the Galactic center do not come from the MAD of Sgr A*. We estimate the cosmic ray (CR) intensity from Sgr A*, but it is too low to explain the high-energy CR intensity on Earth.

Keywords: low-luminosity active galactic nuclei; radio active galactic nuclei; non-thermal radiation sources; cosmic rays; gamma-rays; accretion
Damped Lyα Absorbers in Star-forming Galaxies at z < 0.15 Detected with the Hubble Space Telescope and Implications for Galactic Evolution

We report Hubble Space Telescope Cosmic Origins Spectrograph spectroscopy of 10 quasars with foreground star-forming galaxies at 0.02 < z < 0.14 within impact parameters of ~1-7 kpc. We detect damped/sub-damped Lyα (DLA/sub-DLA) absorption in 100% of cases where no higher-redshift Lyman-limit systems extinguish the flux at the expected wavelength of Lyα absorption, obtaining the largest targeted sample of DLA/sub-DLAs in low-redshift galaxies. We present absorption measurements of neutral hydrogen and metals. Additionally, we present Green Bank Telescope 21 cm emission measurements for five of the galaxies (including two detections). Combining our sample with the literature, we construct a sample of 117 galaxies associated with DLA/sub-DLAs spanning 0 < z < 4.4, and examine trends between gas and stellar properties, and with redshift. The H I column density is anticorrelated with impact parameter and stellar mass. More massive galaxies appear to have gas-rich regions out to larger distances. The specific star formation rate (sSFR) of absorbing galaxies increases with redshift and decreases with M*, consistent with evolution of the star formation main sequence (SFMS). However, ~20% of absorbing galaxies lie below the SFMS, indicating that some DLA/sub-DLAs trace galaxies with longer-than-typical gas-depletion timescales. Most DLA/sub-DLA galaxies with 21 cm emission have higher H I masses than typical galaxies with comparable M*. High M HI/M* ratios and high sSFRs in DLA/sub-DLA galaxies with M* < 109 M ⊙ suggest these galaxies may be gas-rich because of recent gas accretion rather than inefficient star formation. Our study demonstrates the power of absorption and emission studies of DLA/sub-DLA galaxies for extending galactic evolution studies to previously under-explored regimes of low M* and low SFR.

Keywords: observational cosmology; galaxy evolution; star formation; quasar absorption line spectroscopy; interstellar medium
Constraining the Delay Time Distribution of Compact Binary Objects from the Stochastic Gravitational-wave Background Searches

The initial separation of massive star binaries sets the timescale over which their compact remnants merge through the emission of gravitational waves. We show that the delay time distribution (DTD) of binary neutron stars or black holes can be inferred from the stochastic gravitational wave background (SGWB). If the DTD of a population is long, most of the mergers take place at low redshifts and the background would be rather quiet compared to a scenario in which the DTD is short leading to few individual detections at low redshift but a rather loud background. We show that different DTDs predict a factor of 5 difference in the magnitude of the gravitational wave background energy density ( ${{\rm{\Omega }}}_{\mathrm{GW}}$ ) and have the dominant effect on ${{\rm{\Omega }}}_{\mathrm{GW}}$ over other factors such as the mass function of the primary BH mass, $p({m}_{1})$ , the maximum considered BH mass ( ${M}_{\max }$ ), and the effective spin of the black hole ( ${\chi }_{\mathrm{eff}}$ ). A nondetection of such a background can rule out the short DTD scenario. We show that SGWB searches can rule out the short DTD scenario for the BBHs within about four years of observing time at advanced LIGO design sensitivity for a local merger rate of 30 ${\mathrm{Gpc}}^{-3}{\mathrm{yr}}^{-1}$ assuming $p({m}_{1})\propto {m}_{1}^{-1}$ , and ${M}_{\max }=50{M}_{\odot }$ .

Keywords: gravitational wave astronomy; astrophysical black holes; neutron stars; gravitational wave sources; gravitational wave detectors
A New Constraint on the Nuclear Equation of State from Statistical Distributions of Compact Remnants of Supernovae

Understanding how matter behaves at the highest densities and temperatures is a major open problem in both nuclear physics and relativistic astrophysics. Our understanding of such behavior is often encapsulated in the so-called high-temperature nuclear equation of state (EOS), which influences compact binary mergers, core-collapse supernovae, and other phenomena. Our focus is on the type (either black hole or neutron star) and mass of the remnant of the core collapse of a massive star. For each six candidates of equations of state, we use a very large suite of spherically symmetric supernova models to generate a sample of synthetic populations of such remnants. We then compare these synthetic populations to the observed remnant population. Our study provides a novel constraint on the high-temperature nuclear EOS and describes which EOS candidates are more or less favored by an information-theoretic metric.

Keywords: nuclear astrophysics; neutron stars; stellar mass black holes; astrophysical black holes; astrostatistics techniques; core-collapse supernovae; computational astronomy
A Novel Inversion Method to Determine the Coronal Magnetic Field Including the Impact of Bound-Free Absorption

The magnetic field governs the corona; hence, it is a crucial parameter to measure. Unfortunately, existing techniques for estimating its strength are limited by strong assumptions and limitations. These techniques include photospheric or chromospheric field extrapolation using potential or nonlinear force-free methods, estimates based on coronal seismology, or direct observations via, e.g., the Cryo-NIRSP instrument on DKIST, which will measure the coronal magnetic field but only off the limb. Alternately, in this work, we investigate a recently developed approach based on the magnetic-field-induced transition (MIT) of Fe X 257.261Å In order to examine this approach, we have synthesized several Fe X lines from two 3D magnetohydrodynamic simulations, one modeling an emerging flux region and the second an established mature active region. In addition, we take bound-free absorption from neutral hydrogen and helium and singly ionized helium into account. The absorption from cool plasma that occurs at coronal heights has a significant impact on determining the magnetic field. We investigate in detail the challenges of using these Fe X lines to measure the field, considering their density and temperature dependence. We present a novel approach to deriving the magnetic field from the MIT using inversions of the differential emission measure as a function of the temperature, density, and magnetic field. This approach successfully estimates the magnetic field strength (up to 18% relative error) in regions that do not suffer from significant absorption and that have relatively strong coronal magnetic fields (>250 G). This method allows regions where absorption is significant to be masked.

Keywords: active solar corona; solar active region magnetic fields; solar coronal lines; solar ultraviolet emission; solar extreme ultraviolet emission
On the Origin of the Split Main Sequences of the Young Massive Cluster NGC 1856

The detection of split main sequences (MSs) associated with young clusters (≲600 Myr) has attracted a lot of attention. A prevailing scenario is that a bimodality of stellar rotation distribution drives the bifurcation of the MS. Nevertheless, the origin of the stellar rotation dichotomy remains unclear. Hypotheses involving tidally locked binaries or blue straggler stars (BSSs) have been proposed to explain the observed split MSs. This work examines if the long-term dynamical evolution of star clusters can produce the observed split MSs, through high-performance N-body simulation. For example, the young massive cluster NGC 1856 exhibits an apparent MS bifurcation. Our simulation reports that at the age of NGC 1856, tidally locked binaries are fully mixed with single stars. This is consistent with the observation that there is no significant spatial difference between blue MS and red MS stars. However, we find that only high-mass-ratio binaries can evolve to the tidally locked phase at the age of the NGC 1856. These tidally locked binaries will populate a much redder sequence than the MS of single stars rather than a blue MS, which is inconsistent with the hypothesis. The number of tidally locked binaries cannot account for the observation. Our simulation shows that BSSs produced by binary interactions do populate in the blue periphery as shown in a color-magnitude diagram, and their spatial distribution shows a similar pattern of single stars. However, the number of BSSs does not fit the observation.

Keywords: star clusters; close binary stars; blue straggler stars; n-body simulations
A Weighted Analysis to Improve the X-Ray Polarization Sensitivity of the Imaging X-ray Polarimetry Explorer

Imaging X-ray Polarimetry Explorer (IXPE) is a Small Explorer mission that was launched at the end of 2021 to measure the polarization of X-ray emission from tens of astronomical sources. Its focal-plane detectors are based on the Gas Pixel Detector, which measures the polarization by imaging photoelectron tracks in a gas mixture and reconstructing their initial directions. The quality of the single track, and then the capability of correctly determining the original direction of the photoelectron, depends on many factors, e.g., whether the photoelectron is emitted at low or high inclination with respect to the collection plane or the occurrence of a large Coulomb scattering close to the generation point. The reconstruction algorithm used by IXPE to obtain the photoelectron emission direction also calculates several properties of the shape of the tracks that characterize the process. In this paper we compare several such properties and identify the best one to weight each track on the basis of the reconstruction accuracy. We demonstrate that significant improvement in sensitivity can be achieved with this approach and for this reason it will be the baseline for IXPE data analysis.

Keywords: polarimeters; x-ray astronomy; x-ray detectors; astronomy data analysis