adsabs/SciX_UAT_keywords huggingface dataset:
The Direction of the Flow of Interstellar Neutral H Based on Photometric Observations from SOHO/SWAN

Interstellar neutral hydrogen flows into the heliosphere as a mixture of the primary and secondary populations from two somewhat different directions due to splitting occurring in the magnetized outer heliosheath. The direction of the inflow of interstellar neutral H observed in the inner heliosphere, confronted with that of the unperturbed flow of interstellar neutral helium, is important for understanding the geometry of the distortion of the heliosphere from axial symmetry. It is also needed for facilitating remote-sensing studies of the solar wind structure based on observations of the helioglow, such as those presently performed by SOHO/SWAN, and in the near future by IMAP/GLOWS. In the past, the only means to measure the direction of the flow of interstellar hydrogen were spectroscopic observations of the helioglow. Here, we propose a new method to determine this parameter based on a long series of photometric observations of the helioglow. The method is based on purely geometric considerations and does not depend on any model and absolute calibration of the measurements. We apply this method to sky maps of the helioglow available from the SOHO/SWAN experiment and derive the mean longitude of the flow of interstellar hydrogen. We obtain 253.°1 ± 2.°8, which is in perfect agreement with the previously obtained results based on spectroscopic observations.

Keywords: interstellar medium wind; astrospheres; heliosphere; astrosphere interstellar medium interactions
ALMA Observation of SO2 Gas Originating from Io's Volcanic Plume and Lava Areas

We detected the submillimeter spectrum of SO2 gas originating from volcanic plumes and lava areas in Jupiter's moon Io by analyzing the ALMA archive data observed before and after ingress on 2018 March. As a result of synthesis imaging, high intensity regions of SO2 were found to be associated with the volcanically active areas around the Amaterasu Patera (305°W, 38°N) and around the Janus Patera (36°W, 4°S) and Kanehekili Fluctus (32°W, 17°S). By fitting the spectral lineshapes, the main and redshifted spectral components are identified around the Amaterasu Patera. The redshifted component can be attributed as the emission from the plume gas moving away in the line of sight. The rotational temperature and column density of SO2 were derived by employing the population diagram plots with spectral line intensities. The column densities of SO2 before ingress are (2.2 ± 1.1) × 1015 cm-2 around the Amaterasu Patera and (2.2 ± 1.1) × 1015 cm-2 around the Janus Patera. After ingress, the column densities are (1.8 ± 1.2) × 1015 cm-2 and (2.1 ± 0.1) × 1015 cm-2, respectively. This suggests that volcanic eruptions maintain the atmospheres in these regions during eclipse. The temperature around the Amaterasu Patera of 95 ± 28 K before ingress is similar to the temperature of 108 ± 48 K after ingress. On the other hand, the temperature around the Janus Patera increases from 151 ± 70 K before ingress to 311 ± 41 K after ingress. The result suggests that the atmospheric SO2 around the Janus Patera after ingress may be supplied by evaporation from the lava areas.

Keywords: planetary atmospheres
A White Dwarf with Transiting Circumstellar Material Far outside the Roche Limit

We report the discovery of a white dwarf exhibiting deep, irregularly shaped transits, indicative of circumstellar planetary debris. Using Zwicky Transient Facility DR2 photometry of ZTF J013906.17+524536.89 and follow-up observations from the Las Cumbres Observatory, we identify multiple transit events that recur every ≈107.2 days, much longer than the 4.5-4.9 hr orbital periods observed in WD 1145+017, the only other white dwarf known with transiting planetary debris. The transits vary in both depth and duration, lasting 15-25 days and reaching 20%-45% dips in flux. Optical spectra reveal strong Balmer lines, identifying the white dwarf as a DA with ${T}_{\mathrm{eff}}=10,530\pm 140\,{\rm{K}}$ and $\mathrm{log}(g)=7.86\pm 0.06$ . A Ca II K absorption feature is present in all spectra both in and out of transit. Spectra obtained during one night at roughly 15% transit depth show increased Ca II K absorption with a model atmospheric fit suggesting [Ca/H] = -4.6 ± 0.3, whereas spectra taken on three nights out of transit have [Ca/H] of -5.5, -5.3, and -4.9 with similar uncertainties. While the Ca II K line strength varies by only 2σ, we consider a predominantly interstellar origin for Ca absorption unlikely. We suggest a larger column density of circumstellar metallic gas along the line of site or increased accretion of material onto the white dwarf's surface are responsible for the Ca absorption, but further spectroscopic studies are required. In addition, high-speed time series photometry out of transit reveals variability with periods of 900 and 1030 s, consistent with ZZ Ceti pulsations.

Keywords: debris disks; circumstellar dust; planetesimals; stellar pulsations; tidal disruption; circumstellar gas; white dwarf stars; eclipses; transits; roche limit
Preparation of Acetylenediol (HOCCOH) and Glyoxal (HCOCHO) in Interstellar Analog Ices of Carbon Monoxide and Water

Enols—tautomers of ketones or aldehydes—are considered key intermediates in the formation of prebiotic sugars and sugar acids. Although laboratory simulation experiments suggest that enols should be ubiquitous in the interstellar medium, the underlying formation mechanisms of enols in interstellar environments are largely elusive. Here, we present the laboratory experiments on the formation of glyoxal (HCOCHO) along with its ynol tautomer acetylenediol (HOCCOH) in interstellar ice analogs composed of carbon monoxide (CO) and water (H2O) upon exposure to energetic electrons as a proxy for secondary electrons generated from Galactic cosmic rays. Utilizing tunable vacuum ultraviolet photoionization reflectron time-of-flight mass spectrometry, glyoxal and acetylenediol were detected in the gas phase during temperature-programmed desorption. Our results reveal the formation pathways of glyoxal via radical–radical recombination of two formyl (HĊO) radicals, and that of acetylenediol via keto-enol-ynol tautomerization. Due to the abundance of carbon monoxide and water in interstellar ices, glyoxal and acetylenediol are suitable candidates for future astronomical searches. Furthermore, the detection of acetylenediol in astrophysically relevant ices advances our understanding for the formation pathways of high-energy tautomers such as enols in deep space.

Keywords: laboratory astrophysics; astrochemistry; radical-radical recombination; complex organic molecules; interstellar molecules
Predicting the Arrival Time of an Interplanetary Shock Based on DSRT Spectrum Observations for the Corresponding Type II Radio Burst and a Blast Wave Theory

Since fast head-on coronal mass ejections and their associated shocks represent potential hazards to the space environment of the Earth and even other planets, forecasting the arrival time of the corresponding interplanetary shock is a priority in space weather research and prediction. Based on the radio spectrum observations of the 16-element array of the Daocheng Solar Radio Telescope (DSRT), the flagship instrument of the Meridian Project of China, during its construction, this study determines the initial shock speed of a type II solar radio burst on 2022 April 17 from its drifting speed in the spectrum. Assuming that the shock travels at a steady speed during the piston-driven phase (determined from the X-ray flux of the associated flare) and then propagates through interplanetary space as a blast wave, we estimate the propagation and arrival time of the corresponding shock at the orbit of the Solar Terrestrial Relations Observatory-A (STEREO-A). The prediction shows that the shock will reach STEREO-A at 14:31:57 UT on 2022 April 19. The STEREO-A satellite detected an interplanetary shock at 13:52:12 UT on the same day. The discrepancy between the predicted and observed arrival time of the shock is only 0.66 hr. The purpose of this paper is to establish a general method for predicting the shock's propagation and arrival time from this example, which will be utilized to predict more events in the future based on the observations of ground-based solar radio spectrometers or telescopes like DSRT.

Keywords: solar coronal mass ejections; interplanetary shocks; radio bursts; space weather; theoretical models
Viewing Angle Effects in Quasar Application to Cosmology

The symmetry axes of active galactic nuclei (AGNs) are randomly distributed in space, but highly inclined sources are heavily obscured and are not seen as quasars with broad emission lines. The obscuring torus geometry determines the average viewing angle, and if the torus geometry changes with the redshift, this average viewing angle will also change. Thus, the ratio between the isotropic luminosity and observed luminosity may change systematically with redshift. Therefore, if we use quasars to measure the luminosity distance by evaluating the isotropic absolute luminosity and measuring the observed flux, we can have a redshift-dependent bias that can propagate to cosmological parameters. We propose a toy model for testing the effect of viewing angle uncertainty on the measurement of the luminosity distance. The model is based on analytical description of the obscuring torus applied to one-parameter observational data. It illustrates the possible change of the torus covering factor between the two chosen redshift ranges. We have estimated the possible errors in specific cosmological parameters (H0, Ωm) for the flat Lambda cold dark matter cosmology if a method is calibrated at low redshift and applied to the higher redshift. The errors in the cosmological parameters due to potential dependence of the viewing angle on redshift are found to be potentially significant, and the effect will have to be accommodated in the future in all quasar-based cosmological methods. A careful systematic study of AGNs means that a viewing angle across the redshift is necessary, with the use of appropriate samples and models that uniquely determine the inclination of each source.

Keywords: cosmology; galaxies; quasars
The Brittle Boulders of Dwarf Planet Ceres

We mapped all boulders larger than 105 m on the surface of dwarf planet Ceres using images of the Dawn framing camera acquired in the Low Altitude Mapping Orbit. We find that boulders on Ceres are more numerous toward high latitudes and have a maximum lifetime of 150 ± 50 Ma, based on crater counts. These characteristics are distinctly different from those of boulders on asteroid (4) Vesta, an earlier target of Dawn, which implies that Ceres' boulders are mechanically weaker. Clues to their properties can be found in the composition of Ceres' complex crust, which is rich in phyllosilicates and salts. As water ice is thought to be present only meters below the surface, we suggest that boulders also harbor ice. Furthermore, the boulder size-frequency distribution is best fit by a Weibull distribution rather than the customary power law, just like for Vesta boulders. This finding is robust in light of possible types of size measurement error.

Keywords: ceres; dwarf planets; asteroid surfaces; impact phenomena
Cosmological Constraints from the Redshift Dependence of the Alcock-Paczynski Effect: Possibility of Estimating the Nonlinear Systematics Using Fast Simulations

The tomographic Alcock-Paczynski (AP) method is so far the best method in separating the AP signal from the redshift space distortion (RSD) effects and deriving powerful constraints on cosmological parameters using the $\lesssim 40\,{h}^{-1}\ \mathrm{Mpc}$ ≲ 40 h - 1 Mpc clustering region. To guarantee that the method can be easily applied to the future large-scale structure surveys, we study the possibility of estimating the systematics of the method using the fast simulation method. The major contribution of the systematics comes from the nonzero redshift evolution of the RSD effects, which is quantified by ${\hat{\XI }}_{{\rm{\Delta }}s}(\mu ,z)$ ξ ̂ Δ s ( μ , z ) in our analysis, and estimated using the BigMultidark exact N-body simulation and approximate COmoving Lagrangian Acceleration (COLA) simulation samples. We find about 5%/10% evolution when comparing the ${\hat{\XI }}_{{\rm{\Delta }}s}(\mu ,z)$ ξ ̂ Δ s ( μ , z ) measured as z = 0.5/z = 1 to the measurements at z = 0. We checked the inaccuracy in the 2pCFs computed using COLA, and find it 5-10 times smaller than the intrinsic systematics of the tomographic AP method, indicating that using COLA to estimate the systematics is good enough. Finally, we test the effect of halo bias, and find ≲1.5% change in ${\hat{\XI }}_{{\rm{\Delta }}s}$ ξ ̂ Δ s when varying the halo mass within the range of 2 × 1012-1014 M⊙. We will perform more studies to achieve an accurate and efficient estimation of the systematics in the redshift range of z = 0-1.5.

Keywords: large-scale structure of the universe; cosmology
Exploring Features in the Binary Black Hole Population

Vamana is a mixture model framework that infers the astrophysical distribution of chirp mass, mass ratio, and spin component aligned with the orbital angular momentum for the binary black holes (BBH) population. We extend the mixing components in this framework to also model the redshift evolution of merger rate and report all the major one- and two-dimensional features in the BBH population using the 69 gravitational-wave signals detected with a false alarm rate <1 yr-1 in the third Gravitational-Wave Transient Catalog (GWTC-3). Endorsing our previous report and a recent corroborating report from LIGO Scientific, Virgo, and KAGRA Collaborations, we observe the chirp mass distribution has multiple peaks and a lack of mergers with chirp masses 10-12 M ⊙. In addition, we observe that aligned spins show mass dependence with heavier binaries exhibiting larger spins, the mass ratio shows a dependence on the chirp mass but not on the aligned spin, and the redshift evolution of the merger rate for the peaks in the mass distribution is disparate. These features possibly reflect the astrophysics associated with the BBH formation channels. However, additional observations are needed to improve our limited confidence in them.

Keywords: gravitational wave sources; gravitational wave astronomy
The James Webb Space Telescope Absolute Flux Calibration. I. Program Design and Calibrator Stars

It is critical for James Webb Space Telescope (JWST) science that instrumental units are converted to physical units. We detail the design of the JWST absolute flux calibration program that has the core goal of ensuring a robust flux calibration internal to and between all the science instruments for both point and extended source science. This program will observe a sample of calibration stars that have been extensively vetted based mainly on Hubble Space Telescope, Spitzer Space Telescope, and Transiting Exoplanet Survey Satellite observations. The program uses multiple stars of three different, well-understood types (hot stars, A dwarfs, and solar analogs) to allow for the statistical (within a type) and systematic (between types) uncertainties to be quantified. The program explicitly includes observations to calibrate every instrument mode, further vet the set of calibration stars, measure the instrumental repeatability, measure the relative calibration between subarrays and full frame, and check the relative calibration between faint and bright stars. For photometry, we have set up our calibration to directly support both the convention based on the band average flux density and the convention based on the flux density at a fixed wavelength.

Keywords: flux calibration; infrared telescopes; astronomical instrumentation; early-type stars; a dwarf stars; solar analogs
IXPE Observations of the Quintessential Wind-accreting X-Ray Pulsar Vela X-1

The radiation from accreting X-ray pulsars was expected to be highly polarized, with some estimates for the polarization degree of up to 80%. However, phase-resolved and energy-resolved polarimetry of X-ray pulsars is required in order to test different models and to shed light on the emission processes and the geometry of the emission region. Here we present the first results of the observations of the accreting X-ray pulsar Vela X-1 performed with the Imaging X-ray Polarimetry Explorer. Vela X-1 is considered to be the archetypal example of a wind-accreting, high-mass X-ray binary system, consisting of a highly magnetized neutron star accreting matter from its supergiant stellar companion. The spectropolarimetric analysis of the phase-averaged data for Vela X-1 reveals a polarization degree (PD) of 2.3% ± 0.4% at the polarization angle (PA) of -47.°3 ± 5.°4. A low PD is consistent with the results obtained for other X-ray pulsars and is likely related to the inverse temperature structure of the neutron star atmosphere. The energy-resolved analysis shows the PD above 5 keV reaching 6%-10% and a ~90° difference in the PA compared to the data in the 2-3 keV range. The phase-resolved spectropolarimetric analysis finds a PD in the range 0%-9% with the PA varying between -80° and 40°.

Keywords: pulsars; starlight polarization; neutron stars; high mass x-ray binary stars; magnetic fields; accretion
The Evolution of Lyα Emitter Line Widths from z = 5.7 to z = 6.6

Recent evidence suggests that high-redshift Lyα emitting galaxies (LAEs) with log L(Lyα) > 43.5 erg s-1, referred to as ultraluminous LAEs (ULLAEs), may show less evolution than lower-luminosity LAEs in the redshift range z = 5.7-6.6. Here we explore the redshift evolution of the velocity widths of the Lyα emission lines in LAEs over this redshift interval. We use new wide-field, narrowband observations from Subaru/Hyper Suprime-Cam to provide a sample of 24 z = 6.6 and 12 z = 5.7 LAEs with log L(Lyα) > 43 erg s-1, all of which have follow-up spectroscopy from Keck/DEIMOS. Combining with archival lower-luminosity data, we find a significant narrowing of the Lyα lines in LAEs at log L(Lyα) < 43.25 erg s-1 - somewhat lower than the usual ULLAE definition - at z = 6.6 relative to those at z = 5.7, but we do not see this in higher-luminosity LAEs. As we move to higher redshifts, the increasing neutrality of the intergalactic medium should increase the scattering of the Lyα lines, making them narrower. The absence of this effect in the higher-luminosity LAEs suggests they may lie in more highly ionized regions, self-shielding from the scattering effects of the intergalactic medium.

Keywords: lyman-alpha galaxies; reionization; emission line galaxies; cosmology
Exploring Realistic Nanohertz Gravitational-wave Backgrounds

Hundreds of millions of supermassive black hole binaries are expected to contribute to the gravitational-wave signal in the nanohertz frequency band. Their signal is often approximated either as an isotropic Gaussian stochastic background with a power-law spectrum or as an individual source corresponding to the brightest binary. In reality, the signal is best described as a combination of a stochastic background and a few of the brightest binaries modeled individually. We present a method that uses this approach to efficiently create realistic pulsar timing array data sets using synthetic catalogs of binaries based on the Illustris cosmological hydrodynamic simulation. We explore three different properties of such realistic backgrounds that could help distinguish them from those formed in the early universe: (i) their characteristic strain spectrum, (ii) their statistical isotropy, and (iii) the variance of their spatial correlations. We also investigate how the presence of confusion noise from a stochastic background affects detection prospects of individual binaries. We calculate signal-to-noise ratios of the brightest binaries in different realizations for a simulated pulsar timing array based on the NANOGrav 12.5 yr data set extended to a time span of 15 yr. We find that ~6% of the realizations produce systems with signal-to-noise ratios larger than 5, suggesting that individual systems might soon be detected (the fraction increases to ~41% at 20 yr). These can be taken as a pessimistic prediction for the upcoming NANOGrav 15 yr data set, since it does not include the effect of potentially improved timing solutions and newly added pulsars.

Keywords: gravitational waves; gravitational wave astronomy; gravitational wave sources; supermassive black holes; millisecond pulsars
Transmission of a Seismic Wave Generated by Impacts on Granular Asteroids

In this paper, we use a soft-sphere discrete element method code to simulate the transmission and study the attenuation of a seismic wave. Then, we apply our findings to the different space missions that have had to touch the surface of different small bodies in the solar system. Additionally, we do the same in regard to the seismic wave generated by the hypervelocity impacts produced by the DART and Hayabusa2 missions once the shock wave transforms into a seismic wave. We find that even at very low pressures, such as those present in the interior of asteroids, the seismic wave speed can still be on the order of hundreds of meters per second depending on the velocity of the impact that produces the wave. As expected from experimental measurements, our results show that wave velocity is directly dependent on P 1/6, where P is the total pressure (confining pressure plus wave-induced pressure). Regardless of the pressure of the system and the velocity of the impact (in the investigated range), energy dissipation is extremely high. These results provide us with a way to anticipate the extent to which a seismic wave could have been capable of moving some small particles on the surface of a small body upon contact with a spacecraft. Additionally, this rapid energy dissipation would imply that even hypervelocity impacts should perturb only the external layer of a self-gravitating aggregate on which segregation and other phenomena could take place. This would, in turn, produce a layered structure of which some evidence has been observed.

Keywords: asteroids; n-body simulations; microgravity; impact phenomena; planetary structure; regolith
First Constraints on Growth Rate from Redshift-space Ellipticity Correlations of SDSS Galaxies at 0.16 < z < 0.70

We report the first constraints on the growth rate of the universe, f(z)σ 8(z), with intrinsic alignments (IAs) of galaxies. We measure the galaxy density-intrinsic ellipticity cross-correlation and intrinsic ellipticity autocorrelation functions over 0.16 < z < 0.7 from luminous red galaxies (LRGs) and LOWZ and CMASS galaxy samples in the Sloan Digital Sky Survey (SDSS) and SDSS-III BOSS survey. We detect clear anisotropic signals of IA due to redshift-space distortions. By combining measured IA statistics with the conventional galaxy clustering statistics, we obtain tighter constraints on the growth rate. The improvement is particularly prominent for the LRG, which is the brightest galaxy sample and known to be strongly aligned with underlying dark matter distribution; using the measurements on scales above 10 h -1 Mpc, we obtain $f{\sigma }_{8}={0.5196}_{-0.0354}^{+0.0352}$ (68% confidence level) from the clustering-only analysis and $f{\sigma }_{8}={0.5322}_{-0.0291}^{+0.0293}$ with clustering and IA, meaning 19% improvement. The constraint is in good agreement with the prediction of general relativity, f σ 8 = 0.4937 at z = 0.34. For LOWZ and CMASS samples, the improvement of constraints on f σ 8 is found to be 10% and 3.5%, respectively. Our results indicate that the contribution from IA statistics for cosmological constraints can be further enhanced by carefully selecting galaxies for a shape sample.

Keywords: large-scale structure of the universe; cosmology; accelerating universe; cosmological parameters from large-scale structure; redshift surveys