adsabs/SciX_UAT_keywords huggingface dataset:
Jets with a Twist: The Emergence of FR0 Jets in a 3D GRMHD Simulation of Zero-angular-momentum Black Hole Accretion

Spinning supermassive black holes (BHs) in active galactic nuclei magnetically launch relativistic collimated outflows, or jets. Without angular momentum supply, such jets are thought to perish within 3 orders of magnitude in distance from the BH, well before reaching kiloparsec scales. We study the survival of such jets at the largest scale separation to date, via 3D general relativistic magnetohydrodynamic simulations of rapidly spinning BHs immersed into uniform zero-angular-momentum gas threaded by a weak vertical magnetic field. We place the gas outside the BH sphere of influence, or the Bondi radius, chosen to be much larger than the BH gravitational radius, R B = 103 R g. The BH develops dynamically important large-scale magnetic fields, forms a magnetically arrested disk (MAD), and launches relativistic jets that propagate well outside R B and suppress BH accretion to 1.5% of the Bondi rate, ${\dot{M}}_{{\rm{B}}}$ . Thus, low-angular-momentum accretion in the MAD state can form large-scale jets in Fanaroff–Riley (FR) type I and II galaxies. Subsequently, the disk shrinks and exits the MAD state: barely a disk (BAD), it rapidly precesses, whips the jets around, globally destroys them, and lets 5%–10% of ${\dot{M}}_{{\rm{B}}}$ reach the BH. Thereafter, the disk starts rocking back and forth by angles 90°–180°: the rocking accretion disk (RAD) launches weak intermittent jets that spread their energy over a large area and suppress BH accretion to ≲2% ${\dot{M}}_{{\rm{B}}}$ . Because the BAD and RAD states tangle up the jets and destroy them well inside R B, they are promising candidates for the more abundant, but less luminous, class of FR0 galaxies.

Keywords: high energy astrophysics; active galactic nuclei; black hole physics; relativistic jets; general relativity
Nonzero Phase Shifts of Acoustic Waves in the Lower Solar Atmosphere Measured from Realistic Simulations and Their Role in Local Helioseismology

Previous studies analyzing the evanescent nature of acoustic waves in the lower solar atmosphere, up to 300 km above the photosphere, have shown an unexpected phase shift of an order of 1 s between different heights. Those studies investigated the spectral line Fe I λ6173.3, commonly used for helioseismic measurements. Such phase shifts can contribute to a misinterpretation of the measured travel times in local helioseismology, complicating inferences of, e.g., the deep meridional flow. In this study, we carry out phase shift computations using a simulated, fully radiative, and convective atmosphere from which the Fe I λ6173.3 line is synthesized. The resulting phase shifts as functions of frequency across multiple heights show nonzero values in evanescent waves, similar to what was found in observational data. Comparing the Doppler velocities estimated from the synthesized absorption line with the true velocities directly obtained from the simulated plasma motions, we find substantial differences in phase shifts between the two. This leads us to hypothesize that the nonadiabaticity of the solar atmosphere yields extra phase shift contributions to Doppler velocities. Finally, computing phase differences for different viewing angles reveals a systematic center-to-limb variation, similar to what is present in observations. Overall, this study helps to improve our understanding of the physical cause of the helioseismic center-to-limb effect. *Current Version: 0.00.

Keywords: solar atmosphere; helioseismology; solar interior; solar oscillations
Improved GALEX UV Photometry for 700,000 SDSS Galaxies

The Galaxy Evolution Explorer (GALEX) satellite performed the first and only large-area UV survey, which in tandem with the Sloan Digital Sky Survey (SDSS) has facilitated modeling of the spectral energy distributions of low-redshift galaxies and the determination of various galaxy properties, in particular the star formation rate. However, the relatively crude angular resolution of GALEX (5″) made its images susceptible to blending of sources, resulting in potentially biased far-UV and near-UV (NUV) pipeline photometry. To remedy this issue and take advantage of model-fit photometry, we use the EMphot software to obtain forced GALEX photometry for ~700,000 SDSS galaxies at z < 0.3. Positional priors of target galaxies and potentially contaminating neighbors were taken from SDSS. New photometry is based on the best-fitting of three model profiles: optical-like, exponential, and flat. New photometry mitigates blending present in the original pipeline catalogs, which affected 16% of galaxies at a level of >0.2 mag and 2% at a level of >1 mag. Pipeline NUV magnitudes are severely affected (≳1 mag) when the neighbor is brighter than the target galaxy and within 10″, or when the neighbor is fainter and within ~3″ of the target. New photometry fixes edge-of-detector bias, which affected pipeline photometry by up to 0.1 mag in NUV. We present catalogs with new photometry for GALEX observations of different depths, corresponding to the all-sky imaging survey (AIS), medium imaging survey, and deep imaging survey. Catalogs feature combined magnitudes for multiple detections of the same galaxy in a survey.

Keywords: galaxies; galactic and extragalactic astronomy; galaxy photometry; catalogs; sky surveys; photometry; broad band photometry; ultraviolet photometry; ultraviolet astronomy; near ultraviolet astronomy; star formation; spectral energy distribution
A Transmission Spectrum of the Sub-Earth Planet L98-59 b in 1.1-1.7 μm

With the increasing number of planets discovered by the Transit Exoplanet Survey Satellite, the atmospheric characterization of small exoplanets is accelerating. L98-59 is an M-dwarf hosting a multiplanet system, and so far, four small planets have been confirmed. The innermost planet b is ~15% smaller and ~60% lighter than Earth, and should thus have a predominantly rocky composition. The Hubble Space Telescope observed five primary transits of L98-59 b in 1.1-1.7 μm, and here we report the data analysis and the resulting transmission spectrum of the planet. We measure the transit depths for each of the five transits and, by combination, we obtain a transmission spectrum with an overall precision of ~20 ppm in for each of the 18 spectrophotometric channels. With this level of precision, the transmission spectrum does not show significant modulation, and is thus consistent with a planet without any atmosphere or a planet having an atmosphere and high-altitude clouds or haze. The scenarios involving an aerosol-free, H2-dominated atmosphere with H2O or CH4 are inconsistent with the data. The transmission spectrum also disfavors, but does not rule out, an H2O-dominated atmosphere without clouds. A spectral retrieval process suggests that an H2-dominated atmosphere with HCN and clouds or haze may be the preferred solution, but this indication is nonconclusive. Future James Webb Space Telescope observations may find out the nature of the planet among the remaining viable scenarios.

Keywords: extrasolar rocky planets; exoplanet atmospheres; exoplanet atmospheric composition; transmission spectroscopy; astronomy data analysis
Evidence for Misalignment between Debris Disks and Their Host Stars

We place lower limits on the obliquities between debris disks and their host stars for 31 systems by comparing their disk and stellar inclinations. While previous studies did not find evidence for misalignment, we identify six systems with minimum obliquities falling between ~30°and 60°, indicating that debris disks can be significantly misaligned with their stars. These high-obliquity systems span a wide range of stellar parameters with spectral types K through A. Previous works have argued that stars with masses below 1.2 M ⊙ (spectral types of ~F6) have magnetic fields strong enough to realign their rotation axes with the surrounding disk via magnetic warping; given that we observe high obliquities for relatively low-mass stars, magnetic warping alone is likely not responsible for the observed misalignments. Yet, chaotic accretion is expected to result in misalignments of ~20° at most and cannot explain the larger obliquities found in this work. While it remains unclear how primordial misalignment might occur and what role it plays in determining the spin-orbit alignment of planets, future work expanding this sample is critical toward understanding the mechanisms that shape these high-obliquity systems.

Keywords: debris disks; circumstellar disks; planetary alignment; stellar rotation; planet formation
Tracking the Evolutionary Stage of Protostars through the Abundances of Astrophysical Ices

The physical evolution of young stellar objects (YSOs) is accompanied by an enrichment of the molecular complexity, mainly triggered by the heating and energetic processing of astrophysical ices. In this paper, a study of how the ice column density varies across the protostellar evolution has been performed. Tabulated data of H2O, CO2, CH3OH, and HCOOH observed by ground- and space-based telescopes toward 27 early-stage YSOs were taken from the literature. The observational data show that ice column density and spectral index (α), used to classify the evolutionary stage, are well correlated. A 2D continuum radiative transfer simulation containing bare and ice-covered grains at different levels of cosmic-ray processing were used to calculate the spectral energy distributions in different angle inclinations between face-on and edge-on configurations. The H2O:CO2 ice mixture was used to address the H2O and CO2 column density variation, whereas CH3OH and HCOOH are by-products of the virgin ice after energetic processing. The simulated spectra were used to calculate the ice column densities of YSOs in an evolutionary sequence. As a result, the models show that the ice column density variation of HCOOH with α can be justified by envelope dissipation and energetic processing of ice. On the other hand, the ice column densities are mostly overestimated in the cases of H2O, CO2 and CH3OH, even though the physical and cosmic-ray processing effects are taken into account.

Keywords: astrochemistry; infrared sources; interstellar abundances; laboratory astrophysics; star forming regions
Galaxy Zoo: Clump Scout: Surveying the Local Universe for Giant Star-forming Clumps

Massive, star-forming clumps are a common feature of high-redshift star-forming galaxies. How they formed, and why they are so rare at low redshift, remains unclear. In this paper we identify the largest sample yet of clumpy galaxies (7050) at low redshift using data from the citizen science project Galaxy Zoo: Clump Scout, in which volunteers classified 58,550 Sloan Digital Sky Survey (SDSS) galaxies spanning redshift 0.02 < z < 0.15. We apply a robust completeness correction by comparing with simulated clumps identified by the same method. Requiring that the ratio of clump to galaxy flux in the SDSS u band be greater than 8% (similar to clump definitions used by other works), we estimate the fraction of local star-forming galaxies hosting at least one clump (f clumpy) to be ${3.22}_{-0.34}^{+0.38} \% $ . We also compute the same fraction with a less stringent relative flux cut of 3% ( ${12.68}_{-0.88}^{+1.38} \% $ ), as the higher number count and lower statistical noise of this fraction permit finer comparison with future low-redshift clumpy galaxy studies. Our results reveal a sharp decline in f clumpy over 0 < z < 0.5. The minor merger rate remains roughly constant over the same span, so we suggest that minor mergers are unlikely to be the primary driver of clump formation. Instead, the rate of galaxy turbulence is a better tracer for f clumpy over 0 < z < 1.5 for galaxies of all masses, which supports the idea that clump formation is primarily driven by violent disk instability for all galaxy populations during this period.

Keywords: starburst galaxies; galaxies; galaxy evolution; galaxy formation; galaxy structure; cosmological evolution
Photochemistry and Heating/Cooling of the Multiphase Interstellar Medium with UV Radiative Transfer for Magnetohydrodynamic Simulations

We present an efficient heating/cooling method coupled with chemistry and UV radiative transfer that can be applied to numerical simulations of the interstellar medium (ISM). We follow the time-dependent evolution of hydrogen species (H2, H, H+), assume carbon/oxygen species (C, C+, CO, O, and O+) are in formation-destruction balance given the nonsteady hydrogen abundances, and include essential heating/cooling processes needed to capture the thermodynamics of all ISM phases. UV radiation from discrete point sources and the diffuse background is followed through adaptive ray tracing and a six-ray approximation, respectively, allowing for H2 self-shielding; cosmic-ray heating and ionization are also included. To validate our methods and demonstrate their application for a range of density, metallicity, and radiation fields, we conduct a series of tests, including the equilibrium curves of thermal pressure versus density, the chemical and thermal structure in photodissociation regions, H I-to-H2 transitions, and the expansion of H II regions and radiative supernova remnants. Careful treatment of photochemistry and cosmic-ray ionization is essential for many aspects of ISM physics, including identifying the thermal pressure at which cold and warm neutral phases coexist. We caution that many current heating and cooling treatments used in galaxy formation simulations do not reproduce the correct thermal pressure and ionization fraction in the neutral ISM. Our new model is implemented in the MHD code Athena and incorporated in the TIGRESS simulation framework, for use in studying the star-forming ISM in a wide range of environments.

Keywords: interstellar phases; astrochemistry; hydrodynamical simulations; radiative magnetohydrodynamics; interstellar radiation field; photodissociation regions; h ii regions; supernova remnants
Ultra-delayed Neutrino-driven Explosion of Rotating Massive-star Collapse

Long-term neutrino-radiation hydrodynamics simulations in full general relativity are performed for the collapse of rotating massive stars that are evolved from He-stars with initial masses of 20 and 32 M⊙. It is shown that if the collapsing stellar core has sufficient angular momentum, the rotationally supported proto-neutron star (PNS) survives for seconds accompanying the formation of a massive torus of mass larger than 1 M⊙. Subsequent mass accretion onto the central region produces a massive and compact central object, and eventually enhances the neutrino luminosity beyond 1053 erg s-1, resulting in a very delayed neutrino-driven explosion, in particular toward the polar direction. The kinetic energy of the explosion can be appreciably higher than 1052 erg for a massive progenitor star and compatible with that of energetic supernovae like broad-line type-Ic supernovae. By the subsequent accretion, the massive PNS collapses eventually into a rapidly spinning black hole, which could be a central engine for gamma-ray bursts if a massive torus surrounds it.

Keywords: core-collapse supernovae; type ic supernovae
The HI Mass Function of Star-forming Galaxies at z ≈ 1

We present the first estimate, based on direct HI 21 cm observations, of the HI mass function (HIMF) of star-forming galaxies at z ≈ 1, obtained by combining our measurement of the scaling relation between HI mass (M HI ) and B-band luminosity (M B ) of star-forming galaxies with a literature estimate of the B-band luminosity function at z ≈ 1. We determined the M HI –M B relation by using the GMRT-CATz1 survey of the DEEP2 fields to measure the average HI mass of blue galaxies at z = 0.74–1.45 in three separate M B subsamples. This was done by separately stacking the HI 21 cm emission signals of the galaxies in each subsample to detect, at (3.5–4.4)σ significance, the average HI 21 cm emission of each subsample. We find that the M HI –M B relation at z ≈ 1 is consistent with that at z ≈ 0. We combine our estimate of the M HI –M B relation at z ≈ 1 with the B-band luminosity function at z ≈ 1 to determine the HIMF at z ≈ 1. We find that the number density of galaxies with M HI > 1010 M ⊙ (higher than the knee of the local HI mass function) at z ≈ 1 is a factor of ≈4–5 higher than that at z ≈ 0, for a wide range of assumed scatters in the M HI –M B relation. We rule out the hypothesis that the number density of galaxies with M HI > 1010 M ⊙ remains unchanged between z ≈ 1 and z ≈ 0 at ≳99.7% confidence. This is the first statistically significant evidence for evolution in the HIMF of galaxies from the epoch of cosmic noon.

Keywords: high-redshift galaxies; neutral hydrogen clouds; radio astronomy
Observational Evidence for Hot Wind Impact on Parsec Scales in Low-luminosity Active Galactic Nuclei

Supermassive black holes in galaxies spend the majority of their lifetime in the low-luminosity regime, powered by hot accretion flow. Strong winds launched from the hot accretion flow have the potential to play an important role in active galactic nuclei (AGN) feedback. Direct observational evidence for these hot winds with temperatures around 10 keV, has been obtained through the detection of highly ionized iron emission lines with Doppler shifts in two prototypical low-luminosity AGNs, namely M81* and NGC 7213. In this work, we further identify blueshifted H-like O/Ne emission lines in the soft X-ray spectra of these two sources. These lines are interpreted to be associated with additional outflowing components possessing velocity around several 103 km s‑1 and lower temperature (∼0.2–0.4 keV). Blueshifted velocity and the X-ray intensity of these additional outflowing components are hard to explain by previously detected hot wind freely propagating to larger radii. Through detailed numerical simulations, we find the newly detected blueshifted emission lines would come from circumnuclear gas shock-heated by the hot wind instead. Hot wind can provide a larger ram pressure force on the clumpy circumnuclear gas than the gravitational force from the central black hole, effectively impeding the black hole accretion of gas. Our results provide strong evidence for the energy and momentum feedback by the hot AGN wind.

Keywords: low-luminosity active galactic nuclei; agn host galaxies; supermassive black holes; accretion
Existence of the Metal-rich Stellar Halo and High-velocity Thick Disk in the Galaxy

Based on the second Gaia data release (DR2), combined with the LAMOST and APOGEE spectroscopic surveys, we study the kinematics and metallicity distribution of the high-velocity stars that have a relative speed of at least 220 $\mathrm{km}\ {{\rm{s}}}^{-1}$ with respect to the local standard of rest in the Galaxy. The rotational velocity distribution of the high-velocity stars with [Fe/H] $\gt \ -1.0$ dex can be well described by a two-Gaussian model, with peaks at ${V}_{\phi }\sim +164.2\pm 0.7$ and ${V}_{\phi }\sim +3.0\pm 0.3$ $\mathrm{km}\ {{\rm{s}}}^{-1}$ , associated with the thick disk and halo, respectively. This implies that there should exist a high-velocity thick disk (HVTD) and a metal-rich stellar halo (MRSH) in the Galaxy. The HVTD stars have the same position as the halo in the Toomre diagram but show the same rotational velocity and metallicity as the canonical thick disk. The MRSH stars have basically the same rotational velocity, orbital eccentricity, and position in the Lindblad and Toomre diagram as the canonical halo stars, but they are more metal-rich. Furthermore, the metallicity distribution function of our sample stars are well fitted by a four-Gaussian model, associated with the outer halo, inner halo, MRSH, and HVTD, respectively. Chemical and kinematic properties and age imply that the MRSH and HVTD stars may form in situ.

Keywords: galaxy stellar halos; galaxy stellar disks; galaxy structure; galaxy kinematics; galaxy abundances
A Photometric and Astrometric Study of the Open Clusters NGC 1664 and NGC 6939

This study calculated astrophysical parameters, as well as kinematic and galactic orbital parameters, of the open clusters NGC 1664 and NGC 6939. The work is based on CCD ultraviolet, blue, and visual (UBV) and Gaia photometric and astrometric data from ground- and space-based observations. Considering Gaia Early Data Release 3 (EDR3) astrometric data, we determined membership probabilities of stars located in both of the clusters. We used two-color diagrams to determine the E(B - V) color excesses for NGC 1664 and NGC 6939 as 0.190 ± 0.018 and 0.380 ± 0.025 mag, respectively. Photometric metallicities for the two clusters were estimated as [Fe/H] = -0.10 ± 0.02 dex for NGC 1664 and as [Fe/H] = -0.06 ± 0.01 dex for NGC 6939. Using the reddening and metallicity calculated in the study, we obtained distance moduli and ages of the clusters by fitting PARSEC isochrones to the color-magnitude diagrams based on the most likely member stars. Isochrone fitting distances are 1289 ± 47 pc and 1716 ± 87 pc, which coincide with ages of 675 ± 50 Myr and 1.5 ± 0.2 Gyr for NGC 1664 and NGC 6939, respectively. We also derived the distances to the clusters using Gaia trigonometric parallaxes and compared these estimates with the literature. We concluded that the results are in good agreement with those given by the current study. Present-day mass function slopes were calculated as Γ = -1.22 ± 0.33 and Γ = -1.18 ± 0.21 for NGC 1664 and NGC 6939, respectively, which are compatible with the Salpeter slope. Analyzes showed that both of clusters are dynamically relaxed. The kinematic and dynamic orbital parameters of the clusters were calculated, indicating that the birthplaces of the clusters are outside the solar circle.

Keywords: open star clusters; star clusters; galaxy kinematics; stellar kinematics; hertzsprung russell diagram
Detectability of Late-time Supernova Neutrinos with Fallback Accretion onto Protoneutron Star

We investigate the late-time neutrino emission powered by fallback mass accretion onto a protoneutron star (PNS), using neutrino radiation-hydrodynamic simulations with full Boltzmann neutrino transport. We follow the time evolution of the accretion flow onto the PNS until the system reaches a quasi-steady state. A standing shock wave is commonly formed in the accretion flow, whereas the shock radius varies depending on the mass accretion rate and the PNS mass. A sharp increase in temperature emerges in the vicinity of the PNS (~10 km), which characterizes neutrino emission. Both the neutrino luminosity and the average energy become higher with increasing mass accretion rate and PNS mass. The mean energy of the emitted neutrinos is in the range of 10 ≲ ϵ ≲ 20 MeV, which is higher than that estimated from PNS cooling models (≲10 MeV). Assuming a distance to core-collapse supernova of 10 kpc, we quantify neutrino event rates for Super-Kamiokande (Super-K) and Deep Underground Neutrino Experiment (DUNE). The estimated detection rates are well above the background, and their energy-dependent features are qualitatively different from those expected from PNS cooling models. Another notable feature is that the neutrino emission is strongly flavor dependent, exhibiting that the neutrino event rate hinges on the neutrino oscillation model. We estimate them in the case with the adiabatic Mikheev-Smirnov-Wolfenstein model, and show that the normal and inverted mass hierarchy offer a large number of neutrino detections in Super-K and DUNE, respectively. Hence the simultaneous observation with Super-K and DUNE of fallback neutrinos will provide a strong constraint on the neutrino mass hierarchy.

Keywords: core-collapse supernovae; neutron stars; supernova neutrinos; neutrino telescopes