adsabs/SciX_UAT_keywords huggingface dataset:
On Using Inspiraling Supermassive Binary Black Holes in the PTA Frequency Band as Standard Sirens to Constrain Dark Energy

Supermassive binary black holes (SMBBHs) in galactic centers may radiate gravitational waves (GW) in the nano-Hertz frequency band, which are expected to be detected by pulsar timing arrays (PTAs) in the near future. GW signals from individual SMBBHs at cosmic distances, if detected by PTAs, are potentially powerful standard sirens that can be used to independently measure distances and thus put constraints on cosmological parameters. In this paper, we investigate the constraint that may be obtained on the equation of state (w) of dark energy by using those SMBBHs, expected to be detected by the PTAs in the Square Kilometre Array (SKA) era. By considering both the currently available SMBBH candidates and mock SMBBHs in the universe resulting from a simple galaxy major merger model, we find that ∼200-3000 SMBBHs with chirp mass >109 M⊙ are expected to be detected with a signal-to-noise ratio >10 by SKA-PTA with conservative and optimistic settings and they can be used to put a constraint on w to an uncertainty of Δw ∼ 0.02-0.1. If further information on the mass and mass ratio of those SMBBHs can be provided by electromagnetic observations (e.g., chirp mass uncertainty ≲50%), the constraint may be further improved to a ≲0.01 level, as many more SMBBHs will be detected by SKA-PTA with relatively better distance measurements and can be used as the standard sirens.

Keywords: supermassive black holes; gravitational waves; gravitational wave astronomy; dark energy; cosmological parameters; active galactic nuclei; fisher's information; black hole physics; pulsar timing method
Characterizing the Circumgalactic Medium of the Lowest-mass Galaxies: A Case Study of IC 1613

Using 10 sight lines observed with the Hubble Space Telescope/Cosmic Origins Spectrograph, we study the circumgalactic medium (CGM) and outflows of IC 1613, which is a low-mass (M* ∼ 108 M⊙), dwarf irregular galaxy on the outskirts of the Local Group. Among the sight lines, four are pointed toward UV-bright stars in IC 1613, and the other six sight lines are background QSOs at impact parameters from 6 kpc (<0.1R200) to 61 kpc (0.6R200). We detect a number of Si II, Si III, Si IV, C II, and C IV absorbers, most of which have velocities less than the escape velocity of IC 1613 and thus are gravitationally bound. The line strengths of these ion absorbers are consistent with the CGM absorbers detected in dwarf galaxies at low redshifts. Assuming that Si II, Si III, and Si IV comprise nearly 100% of the total silicon, we find 3% (∼8 × 103 M⊙), 2% (∼7 × 103 M⊙), and 32%-42% [∼(1.0-1.3) × 105 M⊙] of the silicon mass in the stars, interstellar medium, and within 0.6R200 of the CGM of IC 1613. We also estimate the metal outflow rate to be ${\dot{{\rm{M}}}}_{\mathrm{out},{\rm{Z}}}\geqslant 1.1\times {10}^{-5}\,{{\rm{M}}}_{\odot }\,{\mathrm{yr}}^{-1}$ and the instantaneous metal mass loading factor to be ηZ ≥ 0.004, which are in broad agreement with available observation and simulation values. This work is the first time a dwarf galaxy of such low mass is probed by a number of both QSO and stellar sight lines, and it shows that the CGM of low-mass, gas-rich galaxies can be a large reservoir enriched with metals from past and ongoing outflows.

Keywords: circumgalactic medium; local group; magellanic stream; metallicity; dwarf irregular galaxies
On the Color-Metallicity Relation of the Red Clump and the Reddening toward the Magellanic Clouds

The zero point of the reddening toward the Large Magellanic Cloud (LMC) has been the subject of some dispute. Its uncertainty propagates as a systematic error for methods that measure the extragalactic distance scale through knowledge of the absolute extinction of LMC stars. In an effort to resolve this issue, we used three different methods to calibrate the most widely used metric to predict LMC extinction, the intrinsic color of the red clump, (V - I)RC,0, for the inner ∼3° of that galaxy. The first approach was to empirically calibrate the color zero points of the BaSTI isochrones over a wide metallicity range of Δ[Fe/H] ≈ 1.10 using measurements of red clump stars in 47 Tuc, the solar neighborhood, and NGC 6791. From these efforts, we also measure these properties of the solar neighborhood red clump, (V - I, GBP - Ks, G - Ks, GRP - Ks, J - Ks, H - Ks, MI, MKs)RC,0 = (1.02, 2.75, 2.18, 1.52, 0.64, 0.15, -0.23, -1.63). The second and third methods were to compare the observed colors of the red clump to those of Cepheids and RR Lyrae in the LMC. With these three methods, we estimated the intrinsic color of the red clump of the LMC to be (V - I)RC,0,LMC = {≈0.93, 0.91 ± 0.02, 0.89 ± 0.02}, respectively, and similarly, using the first and third methods, we estimated (V - I)RC,0,SMC = {≈0.85, 0.84 ± 0.02}, respectively, for the Small Magellanic Cloud. We estimate the luminosities to be MI,RC,LMC = -0.26 and MI,RC,SMC = -0.37. We show that this has important implications for recent calibrations of the tip of the red giant branch in the Magellanic Clouds used to measure H0.

Keywords: distance indicators; stellar distance; horizontal branch; large magellanic cloud; small magellanic cloud; rr lyrae variable stars; rrab variable stars; cepheid variable stars; stellar evolutionary models
Deep Dielectric Breakdown of Silicates: Microstructural Damage and Implications for Lunar Space Weathering

Solar energetic particle events electrically charge the lunar surface and may produce electric fields sufficient to induce dielectric breakdown in regolith grains. We irradiated series of silicate minerals with electrons to determine their physical and chemical response to deep dielectric charging and subsequent breakdown. Two electrical phenomena, flashovers and subsurface dielectric breakdown, produced damage including erosional and eruptive channels, surface pits, comminuted grains, and melt and vapor deposits. Iron abundances strongly affected the scale of damage and the minimum fluence required to reach dielectric breakdown; higher iron abundances required higher fluences to reach the breakdown threshold and produced more areally dense damage with each event. If dielectric breakdown is a prominent space-weathering process on the Moon, it should contribute to differential weathering signatures across the lunar surface as a function of target composition.

Keywords: lunar regolith; solar energetic particles
A VLA Light Curve Spanning 43.8 yr for the Compact Symmetric Object OQ 208

Compact symmetric objects are young, jetted active galactic nuclei defined in part by their slow radio continuum variability. Radio light curves spanning decades can help characterize their evolutionary trends. Here, we present a preliminary VLA light curve at 1.465 GHz for the compact symmetric object OQ 208, a frequently observed calibrator. The light curve spans 43.8 yr, or about 17% of OQ 208's estimated age. The light curve shows two distinct steady levels separated by a decade-long rise at a rate of about 1% yr-1, corresponding to a cumulative increase of about 12% in flux density.

Keywords: active galactic nuclei; aperture synthesis; radio continuum emission; radio jets; time domain astronomy
Active Learning for Computationally Efficient Distribution of Binary Evolution Simulations

Binary stars undergo a variety of interactions and evolutionary phases, critical for predicting and explaining observations. Binary population synthesis with full simulation of stellar structure and evolution is computationally expensive, requiring a large number of mass-transfer sequences. The recently developed binary population synthesis code POSYDON incorporates grids of MESA binary star simulations that are interpolated to model large-scale populations of massive binaries. The traditional method of computing a high-density rectilinear grid of simulations is not scalable for higher-dimension grids, accounting for a range of metallicities, rotation, and eccentricity. We present a new active learning algorithm, psy-cris, which uses machine learning in the data-gathering process to adaptively and iteratively target simulations to run, resulting in a custom, high-performance training set. We test psy-cris on a toy problem and find the resulting training sets require fewer simulations for accurate classification and regression than either regular or randomly sampled grids. We further apply psy-cris to the target problem of building a dynamic grid of MESA simulations, and we demonstrate that, even without fine tuning, a simulation set of only ~1/4 the size of a rectilinear grid is sufficient to achieve the same classification accuracy. We anticipate further gains when algorithmic parameters are optimized for the targeted application. We find that optimizing for classification only may lead to performance losses in regression, and vice versa. Lowering the computational cost of producing grids will enable new population synthesis codes such as POSYDON to cover more input parameters while preserving interpolation accuracies.

Keywords: astronomical simulations; classification; regression; multiple star evolution
A Reliable Calibration of H II Galaxies Hubble Diagram with Cosmic Chronometers and Artificial Neural Network

The L-σ relation of H II galaxies (HIIGx) calibrated by a distance indicator is a reliable standard candle for measuring the Hubble constant H 0. The most straightforward calibration technique anchors them with the first tier of distance ladders from the same galaxies. Recently another promising method that uses the cosmological model-independent cosmic chronometers as a calibrator has been proposed. We promote this technique by removing the assumptions about the cosmic flatness and using a nonparametric artificial neural network for the data reconstruction process. We observe a correlation between the cosmic curvature density parameter and the slope of the L-σ relation, thereby improving the reliability of the calibration. Using the calibrated HIIGx Hubble diagram, we obtain a Type Ia supernovae Hubble diagram free of the conventional assumption about H 0. Finally we get a value of ${H}_{0}={65.9}_{-2.9}^{+3.0}\,\mathrm{km}\,{{\rm{s}}}^{-1}\,{\mathrm{Mpc}}^{-1}$ , which is compatible with the latest Planck 18 measurement.

Keywords: hubble diagram; h ii regions; standard candles; hubble constant; astronomy data analysis; neural networks; type ia supernovae
A Study of the Merging Dwarf Galaxy VCC322

Galaxy interactions and mergers can enhance or reduce star formation, but a complete understanding of the involved processes is still lacking. The effect of dwarf galaxy mergers is even less clear than their massive counterpart. We present a study on a dwarf merger remnant in the Virgo cluster, VCC322, which might form a triple system with VCC334 and VCC319. We identify a prominent long and straight tail-like substructure that has a size comparable to its host galaxy VCC322. By comparing the color–color (g ‑ r versus r ‑ H) distribution with simple stellar population models, we infer that the metallicity and stellar age of this tail are Z ⋆ ∼ 0.02 Z ⊙ and t ⋆ ∼ 10 Gyr, respectively. In VCC319, we find a sign of isophotal twisting. This suggests that VCC319 may be subject to tidal interaction. An analysis of the Sloan Digital Sky Survey optical spectra of VCC322 indicates mass- and light-weighted ages of about 109.8 yr and 107.5 yr, respectively, indicating an ongoing star formation activity. However, the star formation in VCC322 seems suppressed when compared to other star-forming dwarfs of comparable stellar masses. Our finding of shock excitation of optical emission lines indicates that interaction-induced shock may contribute to the heating of cold gas and suppression of star formation.

Keywords: galaxy evolution; galaxy photometry; galaxy tails; star formation; galaxy mergers
Resolving the Emission Regions of the Crab Pulsar's Giant Pulses

The Crab pulsar has striking radio emission properties, with the two dominant pulse components-the main pulse and the interpulse-consisting entirely of giant pulses. The emission is scattered in both the Crab Nebula and the interstellar medium, causing multipath propagation and thus scintillation. We study the scintillation of the Crab's giant pulses using phased Westerbork Synthesis Radio Telescope data at 1668 MHz. We find that giant pulse spectra correlate at only ~2%, much lower than the one-third correlation expected from a randomized signal imparted with the same impulse response function. In addition, we find that the main pulse and the interpulse appear to scintillate differently; the 2D cross-correlation of scintillation between the interpulse and main pulse has a lower amplitude and is wider in time and frequency delay than the 2D autocorrelation of the main pulses. These lines of evidence suggest that the giant pulse emission regions are extended, and that the main pulse and interpulse arise in physically distinct regions that are resolved by the scattering screen. Assuming the scattering takes place in the nebular filaments, the emission regions are of order a light-cylinder radius, as projected on the sky. With further very long baseline interferometry and multifrequency data, it may be possible to measure the distance to the scattering screens, the size of giant pulse emission regions, and the physical separation between the pulse components.

Keywords: radio pulsars; interstellar scintillation
Confirmation of Water Absorption in the Thermal Emission Spectrum of the Hot Jupiter WASP-77Ab with HST/WFC3

Secondary eclipse observations of hot Jupiters can reveal both their compositions and thermal structures. Previous observations have shown a diversity of hot Jupiter eclipse spectra, including absorption features, emission features, and featureless blackbody-like spectra. We present a secondary eclipse spectrum of the hot Jupiter WASP-77Ab observed between 1 and 5 μm with the Hubble Space Telescope (HST) and the Spitzer Space Telescope. The HST observations show signs of water absorption indicative of a noninverted thermal structure. We fit the data with both a one-dimensional free retrieval and a grid of one-dimensional self-consistent forward models to confirm this noninverted structure. The free retrieval places a 3σ lower limit on the atmospheric water abundance of $\mathrm{log}({n}_{{{\rm{H}}}_{2}{\rm{O}}})\gt -4.78$ and cannot constrain the CO abundance. The grid fit produces a slightly superstellar metallicity and constrains the carbon-to-oxygen ratio to less than or equal to the solar value. We also compare our data to recent high-resolution observations of WASP-77Ab taken with the IGRINS/IGRINS spectrograph. We find that the best-fit model to the IGRINS data gives a reduced chi squared of χ2 ν = 1.32 when compared to the WFC3 data. However, the metallicity derived from the IGRINS data is significantly lower than that derived from our self-consistent model fit. We find that this difference may be due to disequilibrium chemistry, and the varying results between the models applied here demonstrate the model dependence of derived metallicities when comparing to low-resolution, low-wavelength coverage data alone. Future work to combine observations from IGRINS, HST, and the James Webb Space Telescope will improve our estimate of the atmospheric composition of WASP-77Ab.

Keywords: hot jupiters; extrasolar gaseous giant planets; exoplanet atmospheric composition
Turbulent Magnetic Dynamos with Halo Lags, Winds, and Jets

This paper presents scale-invariant/self-similar galactic magnetic dynamo models based on the classic equations and compares them qualitatively to recently observed magnetic fields in edge-on spiral galaxies. We classify the axially symmetric dynamo magnetic field by its separate sources, advected flux, and subscale turbulence. We ignore the diffusion term under plausible physical conditions. There is a time dependence determined by globally conserved quantities. We show that magnetic scale heights increase with radius and wind velocity. We suggest that active galactic nucleus (AGN) outflow is an important element of the large-scale galactic dynamo, based on the dynamo action of increasing subscale vorticity. This leads us to predict a correlation between the morphology of coherent galactic magnetic field (i.e., extended polarized flux) and the presence of an AGN.

Keywords: disk galaxies; extragalactic magnetic fields; cosmic magnetic fields theory
Another Look at Erupting Minifilaments at the Base of Solar X-Ray Polar Coronal "Standard" and "Blowout" Jets

We examine 21 solar polar coronal jets that we identify in soft X-ray images obtained from the Hinode/X-ray telescope (XRT). We identify 11 of these as blowout jets and four as standard jets (with six uncertain), based on their X-ray-spire widths being respectively wide or narrow (compared to the jet's base) in the XRT images. From corresponding extreme ultraviolet (EUV) images from the Solar Dynamics Observatory's (SDO) Atmospheric Imaging Assembly (AIA), essentially all (at least 20 of 21) of the jets are made by minifilament eruptions, consistent with other recent studies. Here, we examine the detailed nature of the erupting minifilaments (EMFs) in the jet bases. Wide-spire ("blowout") jets often have ejective EMFs, but sometimes they instead have an EMF that is mostly confined to the jet's base rather than ejected. We also demonstrate that narrow-spire ("standard") jets can have either a confined EMF, or a partially confined EMF where some of the cool minifilament leaks into the jet's spire. Regarding EMF visibility: we find that in some cases the minifilament is apparent in as few as one of the four EUV channels we examined, being essentially invisible in the other channels; thus, it is necessary to examine images from multiple EUV channels before concluding that a jet does not have an EMF at its base. The sizes of the EMFs, measured projected against the sky and early in their eruption, is 14″ ± 7″, which is within a factor of 2 of other measured sizes of coronal-jet EMFs.

Keywords: solar filament eruptions; solar x-ray emission; solar corona; solar extreme ultraviolet emission
Standard GRB Spectral Models "Misused"?

The standard model characterizing the gamma-ray burst (GRB) spectrum invokes a four-parameter empirical function, the so-called the BAND model. An alternative model named cutoff power law (COMP) implements a power law with an exponential cutoff. These functions achieve almost equally good fits on observed spectra, and are adopted in nearly all of the GRB literature. Here, we reanalyze the sample defined in Li et al. (39 bursts including 944 spectra). We classify the spectra by two methods: (1) checking their corner-corner plots of the posteriors to determine well-constrained β (BAND-better) and unconstrained β (COMP-better) categories; and (2) defining the four groups by difference of the deviance information criterion (DIC). We find inconsistent peaks of the parameter distributions between the BAND-better spectra (α = -0.64 ± 0.28 and ${\mathrm{log}}_{10}({{E}}_{{\rm{p}}})={\mathrm{log}}_{10}(191)\pm 0.41$ ) and the COMP-better spectra (α = -0.96 ± 0.33 and ${\mathrm{log}}_{10}({{E}}_{{\rm{p}}})={\mathrm{log}}_{10}(249)\pm 0.40$ ). With the statistically preferred model and vice versa the misused model defined based on DIC statistics, we also find that the fitted parameters obtained by the misused model (COMP) significantly deviate from those obtained by the statistically preferred model (BAND). This means that if a spectrum is statistically preferred, described as the BAND, applying COMP to derive the spectral parameters will prominently deviate from their intrinsic shape, therefore affecting the physical interpretation. Our analysis indicates that the better or statistically preferred model should be duly examined during GRB spectral analysis. In addition, the β distribution exhibits a bimodal structure containing the BAND-better and COMP-better spectra, respectively, implying that BAND and COMP both may have physical origin.

Keywords: gamma-ray bursts; relativistic jets; astronomy data analysis
CME-related Large Decreases in the Differential Phase Delay of Tianwen-1 DOR Signals

Differential phase delay is calculated for the differential one-way range (DOR) signals transmitted by Tianwen-1, the first Chinese Mars spacecraft that entered into the Mars orbit on 2021 February 10. Large decreases in the differential phase delay are identified in the DOR signals received by ground stations on 2021 March 23 and June 18. The decreases indicate sizable increases of the total electron content (TEC) along the DOR signal path between Tianwen-1 and the ground stations. The TEC increases are estimated to be 85 and 175 TEC units on 2021 March 23 and June 18, respectively. Evidence shows that they are caused by the sheath regions ahead of the coronal mass ejections (CMEs) that traversed the signal path on both days. The results represent the first observations of CME-related structures by the DOR signals and demonstrate the potential of DOR signals in remote sensing the interplanetary plasma structures in the solar wind.

Keywords: solar wind; solar coronal mass ejections; deep space probes; radio astronomy; remote sensing
Dynamical Tides in Jupiter as Revealed by Juno

The Juno orbiter has continued to collect data on Jupiter's gravity field with unprecedented precision since 2016, recently reporting a nonhydrostatic component in the tidal response of the planet. At the mid-mission perijove 17, Juno registered a Love number k2 = 0.565 ± 0.006 that is -4% ± 1% (1σ) from the theoretical hydrostatic ${k}_{2}^{(\mathrm{hs})}=0.590$ . Here we assess whether the aforementioned departure of tides from hydrostatic equilibrium represents the neglected gravitational contribution of dynamical tides. We employ perturbation theory and simple tidal models to calculate a fractional dynamical correction Δk2 to the well-known hydrostatic k2. Exploiting the analytical simplicity of a toy uniform-density model, we show how the Coriolis acceleration motivates the negative sign in the Δk2 observed by Juno. By simplifying Jupiter's interior into a coreless, fully convective, and chemically homogeneous body, we calculate Δk2 in a model following an n = 1 polytrope equation of state. Our numerical results for the n = 1 polytrope qualitatively follow the behavior of the uniform-density model, mostly because the main component of the tidal flow is similar in each case. Our results indicate that the gravitational effect of the Io-induced dynamical tide leads to Δk2 = - 4% ± 1%, in agreement with the nonhydrostatic component reported by Juno. Consequently, our results suggest that Juno obtained the first unambiguous detection of the gravitational effect of dynamical tides in a gas giant planet. These results facilitate a future interpretation of Juno tidal gravity data with the purpose of elucidating the existence of a dilute core in Jupiter.

Keywords: tides; jupiter; gravitational fields; galilean satellites; planetary interior