adsabs/SciX_UAT_keywords huggingface dataset:
Modeling the 2022 τ-Herculid Outburst

The τ-Herculids (IAU shower number 61 TAH) is a minor meteor shower associated with comet 73P/Schwassmann-Wachmann 3, a Jupiter-family comet that disintegrated into several fragments in 1995. As a consequence of the nucleus breakup, possible increased meteor rates were predicted for 2022. On May 30-31, observation networks around the world reported two distinct peaks of TAH activity, around solar longitudes 69.°02 and 69.°42. This work examines the encounter conditions of the Earth with meteoroids ejected from 73P during the splitting event and on previous perihelion passages. Numerical simulations suggest that the main peak observed in 2022 was caused by meteoroids ejected from the splitting nucleus with four times the typical cometary gas expansion speed. High-resolution measurements performed with the Canadian Automated Meteor Observatory indicate that these meteoroids are fragile, with estimated bulk densities of 250 kg m-3. In contrast with the main peak, the first TAH activity peak in 2022 is best modeled with trails ejected prior to 1960. We find that ordinary cometary activity could have produced other TAH apparitions observed in the past, including in 1930 and 2017. The extension of our model to future years predicts significant returns of the shower in 2033 and 2049.

Keywords: meteor streams; meteoroids; comets
Compositional Constraints of Ice Lobes at the Edge of Martian South Polar Cap and the Possibility for CO2 Ice

As one of the major ice reservoirs on Mars, the south polar layered deposits (SPLD) are mainly composed of water ice and dust except for the perennial CO2 ice deposits on the surface and within buried layers. At the edge of Planum Australe, the Shallow Radar detected the base of two ice lobes, which can be used to estimate their dielectric properties and analyze the components. These measurements, combined with topographic data, allow for the relative permittivity of the lobe materials to be estimated at 2.73 ± 0.67. Under the constraint of the SPLD density, the permittivity value translates to the existence of CO2 ice depending on the dust content. If the dust content is larger than 24%, the lobes are CO2 free and composed of water ice, dust, and pore space. Whereas, for the dust content of <12%, our results suggest that the lobes must contain a certain amount of CO2 ice, which could be an average volume of 30%. When the dust content is between 12% and 24%, the existence of CO2 ice is undetermined. This study improves the understanding of ice deposits at the Martian south polar.

Keywords: mars; martian satellites; radar astronomy; computational methods
MFPIM: A Deep Learning Model Based on Multimodal Fusion Technology for Pulsar Identification

With the development of radio telescope technology, the quantity and types of acquired pulsar candidate data have increased dramatically. However, it is difficult to accurately identify pulsar candidates. Therefore, we propose to use multimodal fusion technology, called the multimodal fusion-based pulsar identification model (MFPIM), to build a deep learning model to improve the efficiency and accuracy of pulsar candidate identification. MFPIM treats each diagnostic plot of pulsar candidates as a modality and uses multiple convolutional neural networks to extract effective features from the diagnostic plots. After fusing the features, the commonality of different modalities in high-dimensional space is obtained to ensure that the model can take full advantage of the complementarity between diagnostic plots and thus identify pulsar candidates, achieved better classification performance than other current supervised learning algorithms. In addition, a channel attention mechanism is used in the model to enable it to learn the importance of different channel features so that the model focuses more on the channel information in the input data that is more meaningful for classification, reducing the model size while extracting pulsar diagnostic map features more accurately. We conducted experiments on the Five-hundred-meter Aperture Spherical radio Telescope (FAST) data set, and the results show that MFPIM can effectively identify the pulsars in the FAST data set with an identification accuracy of over 98%. To further verify the robustness of the model, we applied the MFPIM to the High Time Resolution Universe data set using transfer learning, with the test accuracy and F1 score reaching over 99%.

Keywords: pulsars; radio pulsars; convolutional neural networks
MAMMOTH-Subaru. III. Lyα Halo Identified by Stacking ∼3300 Lyα Emitters at z = 2.2–2.3

In this paper, we present a Lyα halo (LAH) identified by stacking ∼3300 Lyα emitters (LAEs) at z = 2.2–2.3. We carry out imaging observations and data reduction with Subaru/Hyper Suprime-Cam. Our total survey area is ∼12 deg2 and the imaging depths are 25.5–27.0 mag. Using the imaging data, we select 1240 and 2101 LAE candidates at z = 2.2 and 2.3, respectively. We carry out spectroscopic observations of our LAE candidates and data reduction with Magellan/IMACS to estimate the contamination rate of our LAE candidates. We find that the contamination rate of our sample is low (8%). We stack our LAE candidates with a median stacking method to identify the LAH at z = 2. We show that our LAH is detected until ∼100 kpc at the 2σ significance level and likely extended to ∼200 kpc at a surface brightness level of ∼10‑20 erg s‑1 cm‑2 arcsec‑2. Compared to those of previous studies, our LAH is brighter at radii of ∼25–100 kpc, which is not likely caused by the contamination in our sample but by the different redshifts, fields, and selection methods instead. To investigate how central galaxies affect surrounding LAHs, we divide our LAEs into subsamples based on the Lyα luminosity (L Lyα ), rest-frame Lyα equivalent width (EW0), and UV magnitude (M uv). We stack the subsamples and find that higher L Lyα , smaller EW0, and brighter M uv cause more extended halos. Our results suggest that more massive LAEs generally have more extended LAHs.

Keywords: lyman-alpha galaxies; high-redshift galaxies
Interrelation of the Environment of Lyα Emitters and Massive Galaxies at 2 < z < 4.5

We present a comparison of the spatial distributions of Lyα emitters (LAEs) and massive star-forming and quiescent galaxies (SFGs and QGs) at 2 < z < 4.5. We use the photometric redshift catalog to select SFGs and QGs and an LAE catalog from intermediate/narrow bands obtained from the Subaru Telescope and Isaac Newton Telescope in the Cosmic Evolution Survey (COSMOS). We derive the auto-/cross-correlation signals of SFGs, QGs, and LAEs and the galaxy overdensity distributions at the position of them. Whereas the cross-correlation signals of SFGs and QGs are explained solely by their halo mass differences, those of SFGs and LAEs are significantly lower than those expected from their autocorrelation signals, suggesting that some additional physical processes are segregating these two populations. Such segregation of SFGs and LAEs becomes stronger for rest-frame ultraviolet faint LAEs (MUV > -20). From the overdensity distributions, LAEs are located in less dense regions than SFGs and QGs, whereas SFGs and QGs tend to be in the same overdensity distributions. The different spatial distributions of LAEs compared to those of massive galaxies may be attributed to assembly bias or large amounts of neutral hydrogen gas associated with massive halos. These results reinforce the importance of exploring multiple galaxy populations in quantifying the intrinsic galaxy environment of the high-z universe.

Keywords: galaxy environments; high-redshift galaxies; galaxy evolution
Highly Structured Quasar Outflow in SDSS J010612.22+001920.1

Evidence for quasar outflows can be detected via blueshifted broad absorption lines (BALs) in rest-frame ultraviolet spectra of quasars. We have identified 18 narrow absorption line (NAL) systems in the BAL system of SDSS J010612.22+001920.1, indicating that this BAL outflow has achieved a high degree of clumpiness. Moreover, these NAL systems are highly structured in velocity space and separated from each other by the doublet spacings of multiple ionic species, including a sequence of 10 C IV doublets that form arithmetic progression with a common difference of ≈498 $\,\mathrm{km}\,{{\rm{s}}}^{-1}$ . Cases like J010612.22+001920.1 offer strong evidence for the dynamical process of radiative acceleration in quasar outflow, and open up a new way for the research of quasar outflow under the framework of the NAL complex.

Keywords: quasars; broad-absorption line quasar; quasar absorption line spectroscopy
Evolution of Subsurface Zonal and Meridional Flows in Solar Cycle 24 from Helioseismological Data

The results of determinations of the azimuthal and meridional velocities by time-distance helioseismology from Helioseismic and Magnetic Imager on board Solar Dynamics Observatory from 2010 May to 2020 September at latitudes and Stonyhurst longitudes from - 60° to + 60° and depths to about 19 Mm below the photosphere are used to analyze spatiotemporal variations of the solar differential rotation and meridional circulation. The pattern of torsional oscillations, or latitudinal belts of alternating "fast" and "slow" zonal flows migrating from high latitudes toward the equator, is found to extend in the time-latitude diagrams over the whole time interval. The oscillation period is comparable with a doubled solar-activity-cycle and can be described as an extended solar cycle. The zonal-velocity variations are related to the solar-activity level, the local-velocity increases corresponding to the sunspot-number increases and being localized at latitudes where the strongest magnetic fields are recorded. The dramatic growth of the zonal velocities in 2018 appears to be a precursor of the beginning of Solar Cycle 25. The strong symmetrization of the zonal-velocity field by 2020 can be considered another precursor. The general pattern of poleward meridional flows is modulated by latitudinal variations similar to the extended-solar-cycle behavior of the zonal flows. During the activity maximum, these variations are superposed with a higher harmonic corresponding to meridional flows converging to the spot-formation latitudes. Our results indicate that variations of both the zonal and meridional flows exhibit the extended-solar-cycle behavior, which is an intrinsic feature of the solar dynamo.

Keywords: solar differential rotation; solar meridional circulation; helioseismology; solar cycle
Investigating the Accuracy of Virial Cluster Masses: King Model Simulations

Stars form in clusters within giant molecular clouds. Spectroscopic observations can reveal radial velocities from which virial masses can be estimated. The question we are investigating is how accurate these estimates are with respect to the number of stars observed. We simulated virialized clusters with King model distributions and from these clusters we simulated mock observations. From these observations cluster sizes and virial masses are estimated, and empirical distribution functions are constructed. A confidence interval table is produced considering the number of objects observed and the ratio of velocity dispersion to observational uncertainty.

Keywords: young star clusters; star formation; confidence interval; radial velocity
Salt-bearing Disk Candidates around High-mass Young Stellar Objects

Molecular lines tracing the orbital motion of gas in a well-defined disk are valuable tools for inferring both the properties of the disk and the star it surrounds. Lines that arise only from a disk, and not also from the surrounding molecular cloud core that birthed the star or from the outflow it drives, are rare. Several such emission lines have recently been discovered in one example case, those from NaCl and KCl salt molecules. We studied a sample of 23 candidate high-mass young stellar objects (HMYSOs) in 17 high-mass star-forming regions to determine how frequently emission from these species is detected. We present five new detections of water, NaCl, KCl, PN, and SiS from the innermost regions around the objects, bringing the total number of known briny disk candidates to nine. Their kinematic structure is generally disk-like, though we are unable to determine whether they arise from a disk or outflow in the sources with new detections. We demonstrate that these species are spatially coincident in a few resolved cases and show that they are generally detected together, suggesting a common origin or excitation mechanism. We also show that several disks around HMYSOs clearly do not exhibit emission in these species. Salty disks are therefore neither particularly rare in high-mass disks, nor are they ubiquitous.

Keywords: circumstellar disks; star formation; massive stars; stellar accretion disks
The Curious Case of the "Heartworm" Nebula

The curious Galactic features near G357.2-0.2 were observed with the MeerKAT radio interferometer array in the UHF and L bands (0.56-1.68 GHz). There are two possibly related features: a newly identified faint heart-shaped partial shell (the "heart"), and a series of previously known but now much better imaged narrow, curved features (the "worm") interior to the heart. Polarized emission suggests that much of the emission is nonthermal and is embedded in a dense plasma. The filaments of the worm appear to be magnetic structures powered by embedded knots that are sites of particle acceleration. The morphology of the worm broadly resembles some known pulsar wind nebulae (PWNe) but there is no known pulsar or PWN which could be powering this structure. We also present eROSITA observations of the field; no part of the nebula is detected in X-rays, but the current limits do not preclude the existence of a pulsar/PWN of intermediate spin-down luminosity.

Keywords: galactic radio sources; extended radiation sources; rotation powered pulsars; neutron stars; supernova remnants
A Luminous Quasar at Redshift 7.642

Distant quasars are unique tracers to study the formation of the earliest supermassive black holes (SMBHs) and the history of cosmic reionization. Despite extensive efforts, only two quasars have been found at z ≥ 7.5, due to a combination of their low spatial density and the high contamination rate in quasar selection. We report the discovery of a luminous quasar at z = 7.642, J0313-1806, the most distant quasar yet known. This quasar has a bolometric luminosity of 3.6 × 1013L⊙. Deep spectroscopic observations reveal a SMBH with a mass of (1.6 ± 0.4) × 109 M⊙ in this quasar. The existence of such a massive SMBH just ∼670 million years after the big bang challenges significantly theoretical models of SMBH growth. In addition, the quasar spectrum exhibits strong broad absorption line (BAL) features in C IV and Si IV, with a maximum velocity close to 20% of the speed of light. The relativistic BAL features, combined with a strongly blueshifted C IV emission line, indicate that there is a strong active galactic nucleus (AGN)-driven outflow in this system. Atacama Large Millimeter/submillimeter Array observations detect the dust continuum and [C II] emission from the quasar host galaxy, yielding an accurate redshift of 7.6423 ± 0.0013 and suggesting that the quasar is hosted by an intensely star-forming galaxy, with a star formation rate of ∼200 M⊙ yr-1 and a dust mass of ∼7 × 107 M⊙. Follow-up observations of this reionization-era BAL quasar will provide a powerful probe of the effects of AGN feedback on the growth of the earliest massive galaxies.

Keywords: supermassive black holes; quasars; broad-absorption line quasar; early universe
Global Dynamic Scaling Relations of H I-rich Ultra-diffuse Galaxies

The baryonic Tully-Fisher relation (BTFR), which connects the baryonic mass of galaxies with their circular velocities, has been validated across a wide range of galaxies, from dwarf galaxies to massive galaxies. Recent studies have found that several ultra-diffuse galaxies (UDGs) deviate significantly from the BTFR, indicating a galaxy population with abnormal dynamical properties. However, such studies were still confined within a small sample size. In this study, we used the 100% complete Arecibo Legacy Fast Arecibo L-band Feed Array (ALFALFA) to investigate the BTFR of 88 H I-rich UDGs (HUDGs), which is the largest UDG sample with dynamical information. We found that the HUDGs form a continuous distribution in the BTFR diagram, with high-velocity galaxies consistent with normal dwarf galaxies at a 1σ level, and low-velocity galaxies deviating from the BTFR, in line with that reported in the literature. We point out that the observed deviation may be subject to various selection effects or systemic biases. Nevertheless, we found that the significance of the deviation of HUDGs from the BTFR and TFR are different, i.e., they either deviate from the BTFR or from the TFR. Our result indicates that a high gas fraction may play an important role in explaining the deviation of HUDGs from BTFR.

Keywords: dwarf galaxies; low surface brightness galaxies; galaxy dynamics; galaxy formation; galaxy evolution
Supercritical Growth Pathway to Overmassive Black Holes at Cosmic Dawn: Coevolution with Massive Quasar Hosts

Observations of the most luminous quasars at high redshifts (z > 6) have revealed that the largest supermassive black holes (SMBHs) at those epochs tend to be substantially overmassive relative to their host galaxies compared to the local relations, suggesting they experienced rapid early growth phases. We propose an assembly model for the SMBHs that end up in rare massive ~1012 M ⊙ host halos at z ~ 6-7, applying a kinetic feedback prescription for BHs accreting above the Eddington rate, provided by radiation hydrodynamic simulations for the long-term evolution of the accretion-flow structure. The large inflow rates into these halos during their assembly enable the formation of >109 M ⊙ SMBHs by z ~ 6, even starting from stellar-mass seeds at z ~ 30, and even in the presence of outflows that reduce the BH feeding rate, especially at early times. This mechanism also naturally yields a high BH-to-galaxy mass ratio of >0.01 before the SMBH mass reaches M BH > 109 M ⊙ by z ~ 6. These fast-growing SMBH progenitors are bright enough to be detected by upcoming observations with the James Webb Space Telescope over a wide range of redshift (7 < z < 15), regardless of how they were seeded.

Keywords: supermassive black holes; quasars; high-redshift galaxies
20 s Cadence TESS Photometry of HR 8799

We analyzed 20 s cadence Transiting Exoplanet Survey Satellite time-series photometry of the exoplanet host star HR 8799 collected in Sector 56. The amplitude spectrum shows Gamma Doradus (γ Dor) pulsations consistent with previous space-based photometry from MOST. Assuming that HR 8799 is a representative of γ Dor stars in the Kepler sample, the dominant dipole mode at 1.98 cycles day-1 implies a core rotation period of ~0.7 day, which combined with $v\sin i$ and stellar radius measurements would result in a preliminary stellar inclination of ~28° assuming rigid rotation. We find no significant residual photometric variation after removing the pulsation signal aside from a ~9 days trend that is likely a systematic effect or an artifact from performing aggressive frequency subtraction in the presence of red noise.

Keywords: exoplanet systems; gamma doradus variable stars; planet hosting stars; stellar pulsations; variable stars
Preview of Comet C/2021 A1 (Leonard) and Its Encounter with Venus

Long-period comet C/2021 A1 (Leonard) will approach Venus to within 0.029 au on 2021 December 18 and may subsequently graze the planet with its dust trail less than 2 days later. We observed C/2021 A1 with the Lowell Discovery Telescope on 2021 January 13 and March 3, as well as with the Palomar Hale Telescope on 2021 March 20, while the comet was inbound at heliocentric distances of r = 4.97, 4.46, and 4.28 au, respectively. Tail morphology suggests that the dust is optically dominated by ~0.1-1 mm radius grains produced in the prior year. Neither narrowband imaging photometry nor spectrophotometry reveal any definitive gas emission, placing 3σ upper bounds on CN production of ≲1023 molec-1 at both of the latter two epochs. Trajectory analysis indicates that large (≳1 mm) grains ejected at extremely large heliocentric distances (r ≳ 30 au) are most strongly favored to reach Venus. The flux of such meteors on Venus, and thus their potential direct or indirect observability, is highly uncertain, as the comet's dust production history is poorly constrained at these distances but will likely fall well below the meteor flux from comet C/2013 A1 (Siding Spring)'s closer encounter to Mars in 2014 and thus poses a negligible risk to any spacecraft in orbit around Venus. Dust produced in previous apparitions will not likely contribute substantially to the meteor flux, nor will dust from any future activity apart from an unlikely high-speed (≳0.5 km s-1) dust outburst prior to the comet reaching r ≈ 2 au in 2021 September.

Keywords: comet tails; long period comets; meteor trails; venus
A New Reconstruction of the Sun's Magnetic Field and Total Irradiance since 1700

We model the Sun's large-scale magnetic field and total solar irradiance (TSI) since 1700 by combining flux transport simulations with empirical relationships between facular brightening, sunspot darkening, and the total photospheric flux. The photospheric field is evolved subject to the constraints that (1) the flux emergence rate scales as the yearly sunspot numbers, and (2) the polar field strength at solar minimum is proportional to the amplitude of the following cycle. Simulations are performed using both the recently revised sunspot numbers and an average of these numbers and the Hoyt-Schatten group numbers. A decrease (increase) in the polar field strength from one cycle to the next is simulated either by increasing (decreasing) the poleward flow speed, or by decreasing (increasing) the average axial tilts of active regions; the resulting photospheric field evolution is very similar whichever parameter is varied. Comparisons between irradiance data and both the simulated and observed photospheric field suggest that TSI and facular brightness increase less steeply with the field strength at solar minimum than at other phases of the cycle, presumably because of the dominance of small-scale ephemeral regions when activity is very low. This relative insensitivity of the irradiance to changes in the large-scale field during cycle minima results in a minimum-to-minimum increase of annual TSI from 1700 to 1964 (2008) of 0.2 (0.06) W m-2, a factor of 2-3 smaller than predicted in earlier reconstructions where the relation between facular brightness and field strength was assumed to be independent of cycle phase.

Keywords: interplanetary magnetic fields; solar-terrestrial interactions; solar cycle; solar dynamo; solar magnetic fields; solar faculae; ephemeral active regions; solar radiation; sunspots; solar active regions; galactic cosmic rays