adsabs/SciX_UAT_keywords huggingface dataset:
Small-scale Magnetic Flux Ropes in Stream Interaction Regions from Parker Solar Probe and Wind Spacecraft Observations

Using in situ measurements from the Parker Solar Probe and Wind spacecraft, we investigate the small-scale magnetic flux ropes (SFRs) and their properties inside stream interaction regions (SIRs). Within SIRs from ~0.15 to 1 au, SFRs are found to exist in a wide range of solar wind speeds with more frequent occurrences after the stream interface, and the Alfvénicity of these structures decreases significantly with increasing heliocentric distances. Furthermore, we examine the variation of five corresponding SIRs from the same solar sources. The enhancements of suprathermal electrons within these SIRs persist at 1 au and are observed multiple times. An SFR appears to occur repeatedly with the recurring SIRs and is traversed by the Wind spacecraft at least twice. This set of SFRs has similarities in variations of the magnetic field components, plasma bulk properties, density ratio of solar wind alpha and proton particles, and unidirectional suprathermal electrons. We also show, through the detailed time-series plots and Grad-Shafranov reconstruction results, that they possess the same chirality and carry comparable amounts of magnetic flux. Lastly, we discuss the possibility for these recurring SFRs to be formed via interchange reconnection, maintain the connection with the Sun, and survive up to 1 au.

Keywords: solar wind; fast solar wind; astronomy data analysis; solar magnetic reconnection
What Are Those Tiny Things? A First Study of Compact Star Clusters in the SMACS0723 Field with JWST

We use the unprecedented resolution and depth of the JWST NIRCam Early Release Observations at 1-5 μm to study the stellar mass, age, and metallicity of compact star clusters in the neighborhood of the host galaxies in the SMACS J0723.3-7327 galaxy cluster field at z = 0.39. The measured colors of these star clusters show a similar distribution as quiescent galaxies at the same redshift, but are >3 mag fainter than the current depths of wide-field galaxy survey. The star clusters are unresolved in the NIRCam/F150W data suggesting sizes smaller than 50 pc. This is significantly smaller than star-forming clumps or dwarf galaxies in local galaxies. From fitting their photometry with simple stellar population (SSP) models, we find stellar metallicities consistent with 0.2-0.3 Z ⊙ and ages of ${1.5}_{-0.5}^{+0.5}\,\mathrm{Gyr}$ . We rule out metallicities <0.2 Z ⊙ and solar/supersolar at 4σ significance. Assuming mass-to-light ratios obtained from the best-fit SSP, we estimate stellar masses of ${2.4}_{-1.5}^{+3.0}\times {10}^{6}\,{M}_{\odot }$ . These are between average masses of local globular clusters and dwarf galaxies. Our analysis suggests middle-aged globular cluster with relatively recent formation times at z = 0.5-0.7, which could have been subsequently stripped away from their host galaxies due to interactions in the cluster environment or formed in cold flows onto the cluster core. However, we cannot rule out these objects being compact cores of stripped dwarf galaxies.

Keywords: globular star clusters; galaxy clusters; stellar populations; metallicity; galaxy formation; dwarf galaxies
The Radio to GeV Afterglow of GRB 221009A

GRB 221009A (z = 0.151) is one of the closest known long γ-ray bursts (GRBs). Its extreme brightness across all electromagnetic wavelengths provides an unprecedented opportunity to study a member of this still-mysterious class of transients in exquisite detail. We present multiwavelength observations of this extraordinary event, spanning 15 orders of magnitude in photon energy from radio to γ-rays. We find that the data can be partially explained by a forward shock (FS) from a highly collimated relativistic jet interacting with a low-density, wind-like medium. Under this model, the jet's beaming-corrected kinetic energy (E K ~ 4 × 1050 erg) is typical for the GRB population. The radio and millimeter data provide strong limiting constraints on the FS model, but require the presence of an additional emission component. From equipartition arguments, we find that the radio emission is likely produced by a small amount of mass (≲6 × 10-7 M ⊙) moving relativistically (Γ ≳ 9) with a large kinetic energy (≳1049 erg). However, the temporal evolution of this component does not follow prescriptions for synchrotron radiation from a single power-law distribution of electrons (e.g., in a reverse shock or two-component jet), or a thermal-electron population, perhaps suggesting that one of the standard assumptions of afterglow theory is violated. GRB 221009A will likely remain detectable with radio telescopes for years to come, providing a valuable opportunity to track the full lifecycle of a powerful relativistic jet.

Keywords: high energy astrophysics; gamma-ray bursts
Galaxy Clusters from the DESI Legacy Imaging Surveys. I. Cluster Detection

Based on the photometric redshift catalog of Zou et al., we apply a fast clustering algorithm to identify 540,432 galaxy clusters at z ≲ 1 in the DESI legacy imaging surveys, which cover a sky area of about 20,000 deg2. Monte Carlo simulations indicate that the false-detection rate of our detecting method is about 3.1%. The total masses of galaxy clusters are derived using a calibrated richness-mass relation that is based on the observations of X-ray emission and the Sunyaev and Zel'dovich effect. The median redshift and mass of our detected clusters are about 0.53 and 1.23 × 1014 M⊙, respectively. Comparing with previous clusters identified using the data of the Sloan Digital Sky Survey; we can recognize most of them, especially those with high richness. Our catalog will be used for further statistical studies on galaxy clusters and environmental effects on galaxy evolution, etc.

Keywords: galaxy clusters; photometry; sky surveys
Hybrid Comptonization and Electron-Positron Pair Production in the Black-hole X-Ray Binary MAXI J1820+070

We study X-ray and soft gamma-ray spectra from the hard state of the accreting black-hole binary MAXI J1820+070. We perform an analysis of two joint spectra from NuSTAR and INTEGRAL, covering the range of 3-650 keV, and of an average joint spectrum over the rise of the hard state, covering the 3-2200 keV range. The spectra are well modeled by Comptonization of soft seed photons. However, the distributions of the scattering electrons are not purely thermal; we find they have substantial high-energy tails, well modeled as power laws. The photon tail in the average spectrum is detected well beyond the threshold for electron-positron pair production, 511 keV. This allows us to calculate the rate of the electron-positron pair production and put a lower limit on the size of the source from pair equilibrium. At the fitted Thomson optical depth of the Comptonizing plasma, the limit is about 4 gravitational radii. If we adopt the sizes estimated by us from the reflection spectroscopy of >20 gravitational radii, the fractional pair abundance becomes much less than unity. The low pair abundance is confirmed by the lack of both an annihilation feature and of a pair absorption cutoff above 511 keV in the average spectrum.

Keywords: accretion; non-thermal radiation sources; x-ray binary stars; low-mass x-ray binary stars
The Relation between the Optical Fe II Emission and the Dimensionless Accretion Rate for Active Galactic Nuclei

It was suggested that the prominent feature of the optical Fe II emission has a connection with the accretion process in active galactic nuclei (AGN). For a large sample of 4037 quasars (z < 0.8) with measured H β line dispersion (σ Hβ ) selected from the Sloan Digital Sky Survey (SDSS) and 120 compiled reverberation-mapped (RM) AGN, we use σ Hβ and the extended R BLR(Hβ)-L 5100 relation to calculate supermassive black holes masses (M BH) from the single-epoch spectra for the SDSS subsample, and σ Hβ from the mean spectra for the RM subsample. We find a strong correlation between the relative optical Fe II strength R Fe and the dimensionless accretion rate $\dot{{\mathscr{M}}}$ for the SDSS subsample with the Spearman correlation coefficient r s of 0.727, which is consistent with that derived from the mean spectra for the RM subsample. The magnitude of velocity shift of the optical Fe II emission has a strong anticorrelation with $\dot{{\mathscr{M}}}$ , whenever there is inflow or outflow. These strong correlations show that the optical Fe II emission has an intimate connection with the accretion process. Assuming that the difference of M BH is due to the variable virial factor f for adopting FWHM H β as the velocity tracer, we find that there is a relation between f and FWHM H β , $\mathrm{log}f=-(0.41\pm 0.002){\mathrm{logFWHM}}_{H\beta }+(1.719\pm 0.009)$ for the single-epoch spectrum. The relation between $\mathrm{log}f$ and σ Hβ is not too strong, suggesting that σ Hβ does not seem to depend much on the broad-line region inclination and a constant σ-based f is suitable for σ Hβ as the velocity tracer.

Keywords: supermassive black holes; active galactic nuclei; reverberation mapping; quasars
No Evidence for More Earth-sized Planets in the Habitable Zone of Kepler's M versus FGK Stars

Reliable detections of Earth-sized planets in the habitable zone remain elusive in the Kepler sample, even for M dwarfs. The Kepler sample was once thought to contain a considerable number of M-dwarf stars (T eff < 4000 K), which hosted enough Earth-sized ([0.5, 1.5] R ⊕) planets to estimate their occurrence rate (η ⊕) in the habitable zone. However, updated stellar properties from Gaia have shifted many Kepler stars to earlier spectral type classifications, with most stars (and their planets) now measured to be larger and hotter than previously believed. Today, only one partially reliable Earth-sized candidate remains in the optimistic habitable zone, and zero in the conservative zone. Here we performed a new investigation of Kepler's Earth-sized planets orbiting M-dwarf stars, using occurrence rate models with considerations of updated parameters and candidate reliability. Extrapolating our models to low instellations, we found an occurrence rate of ${\eta }_{\oplus }={8.58}_{-8.22}^{+17.94} \% $ for the conservative habitable zone (and ${14.22}_{-12.71}^{+24.96} \% $ for the optimistic one), consistent with previous works when considering the large uncertainties. Comparing these estimates to those from similarly comprehensive studies of Sun-like stars, we found that the current Kepler sample does not offer evidence to support an increase in η ⊕ from FGK to M stars. While the Kepler sample is too sparse to resolve an occurrence trend between early and mid- to late M dwarfs for Earth-sized planets, studies including larger planets and/or data from the K2 and TESS missions are well suited to this task.

Keywords: exoplanets; habitable zone
4FGL J1844.4-0306: High-energy Emission Likely from the Supernova Remnant G29.37 + 0.1

Very-high-energy (VHE) observations have revealed approximately 100 TeV sources in our Galaxy, and a significant fraction of them are under investigation to understand their origin. We report our study of one of them, HESS J1844-030. It is found to be possibly associated with the supernova remnant (SNR) candidate G29.37 + 0.1, and detailed studies of the source region at radio and X-ray frequencies have suggested that this SNR is a composite one, containing a pulsar wind nebula (PWN) powered by a candidate young pulsar. As the GeV source 4FGL J1844.4-0306 is also located in the region with high positional coincidence, we analyze its γ-ray data obtained with the Large Area Telescope on board the Fermi Gamma-ray Space Telescope. We determine the GeV γ-ray emission is extended, described with a log-parabola function. The obtained spectrum can be connected to that of the VHE source HESS J1844-030. Given these properties and those from multifrequency studies, we discuss the origin of the γ-ray emission by considering that the two γ-ray sources are associated. Our modeling indicates that while the TeV part would have either a hadronic (from the SNR) or a leptonic origin (from the putative PWN), the GeV part would arise from a hadronic process. Thus we conclude that 4FGL J1844.4-0306 is likely the GeV counterpart to G29.37 + 0.1.

Keywords: supernova remnants; pulsar wind nebulae; gamma-ray sources
Demonstrating Photon Ring Existence with Single-baseline Polarimetry

Images of supermassive black hole accretion flows contain features of both curved spacetime and plasma structure. Inferring properties of the spacetime from images requires modeling the plasma properties, and vice versa. The Event Horizon Telescope Collaboration has imaged near-horizon millimeter emission from both Messier 87* (M87*) and Sagittarius A* (Sgr A*) with very long baseline interferometry (VLBI) and has found a preference for magnetically arrested disk (MAD) accretion in each case. MAD accretion enables spacetime measurements through future observations of the photon ring, the image feature composed of near-orbiting photons. The ordered fields and relatively weak Faraday rotation of MADs yield rotationally symmetric polarization when viewed at modest inclination. In this letter, we utilize this symmetry along with parallel transport symmetries to construct a gain-robust interferometric quantity that detects the transition between the weakly lensed accretion flow image and the strongly lensed photon ring. We predict a shift in polarimetric phases on long baselines and demonstrate that the photon rings in M87* and Sgr A* can be unambiguously detected with sensitive, long-baseline measurements. For M87*, we find that photon ring detection in snapshot observations requires ~1 mJy sensitivity on >15 Gλ baselines at 230 GHz and above, which could be achieved with space-VLBI or higher-frequency ground-based VLBI. For Sgr A*, we find that interstellar scattering inhibits photon ring detectability at 230 GHz, but ~10 mJy sensitivity on >12 Gλ baselines at 345 GHz is sufficient and is accessible from the ground. For both sources, these sensitivity requirements may be relaxed by repeated observations and averaging.

Keywords: supermassive black holes; very long baseline interferometry; polarimetry; gravitational lensing
A Numerical Model for the Multiwavelength Lightcurves of PSR J0030+0451

Recent modeling of Neutron Star Interior Composition Explorer (NICER) observations of the millisecond pulsar PSR J0030+0451 suggests that the magnetic field of the pulsar is non-dipolar. We construct a magnetic field configuration where foot points of the open field lines closely resemble the hotspot configuration from NICER observations. Using this magnetic field as input, we perform force-free simulations of the magnetosphere of PSR J0030+0451, showing the three-dimensional structure of its plasma-filled magnetosphere. Making simple and physically motivated assumptions about the emitting regions, we are able to construct the multiwavelength lightcurves that qualitatively agree with the corresponding observations. The agreement suggests that multipole magnetic structures are the key to modeling this type of pulsar, and can be used to constrain the magnetic inclination angle and the location of radio emission.

Keywords: millisecond pulsars; magnetospheric radio emissions; x-ray sources; gamma-ray sources; rotation powered pulsars
X-Ray Ionization of Planet-opened Gaps in Protostellar Disks

Young planets with masses approaching Jupiter's have tides strong enough to clear gaps around their orbits in the protostellar disk. Gas flow through the gaps regulates the planets' further growth and governs the disk's evolution. Magnetic forces may drive that flow if the gas is sufficiently ionized to couple to the fields. We compute the ionizing effects of the X-rays from the central young star, using Monte Carlo radiative transfer calculations to find the spectrum of Compton-scattered photons reaching the planet's vicinity. The scattered X-rays ionize the gas at rates similar to or greater than the interstellar cosmic-ray rate near planets with the masses of Saturn and of Jupiter, located at 5 au and at 10 au, in disks with the interstellar mass fraction of sub-micron dust and with the dust depleted by a factor 100. Solving a gas-grain recombination reaction network yields charged particle populations whose ability to carry currents is sufficient to partly couple the magnetic fields to the gas around the planet. Most cases can undergo Hall-shear instability, and some can launch magnetocentrifugal winds. However, the material on the planet's orbit has diffusivities so large in all the cases we examine that magnetorotational turbulence is prevented and the non-ideal terms govern the magnetic field's evolution. Thus the flow of gas in the gaps opened by young giant planets depends crucially on the finite conductivity.

Keywords: protoplanetary disks; radiative transfer; magnetic fields; x-ray stars
The Inhomogeneity Effect. III. Weather Impacts on the Heat Flow of Hot Jupiters

The interior flux of a giant planet impacts atmospheric motion, and the atmosphere dictates the interior's cooling. Here we use a non-hydrostatic general circulation model (Simulating Non-hydrostatic Atmospheres on Planets) coupled with a multi-stream multi-scattering radiative module (High-performance Atmospheric Radiation Package) to simulate the weather impacts on the heat flow of hot Jupiters. We found that the vertical heat flux is primarily transported by convection in the lower atmosphere and regulated by dynamics and radiation in the overlying radiation-circulation zone. The temperature inversion occurs on the dayside and reduces the upward radiative flux. The atmospheric dynamics relay the vertical heat transport until the radiation becomes efficient in the upper atmosphere. The cooling flux increases with atmospheric drag due to increased day-night contrast and spatial inhomogeneity. The temperature dependence of the infrared opacity greatly amplifies the opacity inhomogeneity. Although atmospheric circulation could transport heat downward in a narrow region above the radiative-convective boundary, the opacity inhomogeneity effect overcomes the dynamical effect and leads to a larger overall interior cooling than the local simulations with the same interior entropy and stellar flux. The enhancement depends critically on the equilibrium temperature, drag, and atmospheric opacity. In a strong-drag atmosphere hotter than 1600 K, a significant inhomogeneity effect in three-dimensional (3D) models can boost interior cooling several-fold compared to the 1D radiative-convective equilibrium models. This study confirms the analytical argument of the inhomogeneity effect in the companion papers by Zhang. It highlights the importance of using 3D atmospheric models in understanding the inflation mechanisms of hot Jupiters and giant planet evolution in general.

Keywords: planetary atmospheres; exoplanet atmospheric dynamics; exoplanet evolution; exoplanet atmospheric structure
Resolving Clumpy versus Extended Lyα in Strongly Lensed, High-redshift Lyα Emitters

We present six strongly gravitationally lensed Lyα emitters (LAEs) at z ∼ 4–5 with Hubble Space Telescope (HST) narrowband imaging isolating Lyα. Through complex radiative transfer Lyα encodes information about the spatial distribution and kinematics of the neutral hydrogen upon which it scatters. We investigate the galaxy properties and Lyα morphologies of our sample. Many previous studies of high-redshift LAEs have been limited in Lyα spatial resolution. In this work we take advantage of high-resolution Lyα imaging boosted by lensing magnification, allowing us to probe subgalactic scales that are otherwise inaccessible at these redshifts. We use broadband imaging from HST (rest-frame UV) and Spitzer (rest-frame optical) in spectral energy distribution fitting, providing estimates of the stellar masses (∼108–109 M ⊙), stellar population ages (t 50 < 40 Myr), and amounts of dust (A V ∼ 0.1–0.6, statistically consistent with zero). We employ nonparametric star formation histories to probe the young stellar populations which create the Lyα. We also examine the offsets between the Lyα and stellar continuum, finding small upper limits of offsets (<0.″1) consistent with studies of low-redshift LAEs, indicating our galaxies are not interacting or merging. Finally, we find a bimodality in our sample's Lyα morphologies: clumpy and extended. We find a suggestive trend: our LAEs with clumpy Lyα are generally younger than the LAEs with extended Lyα, suggesting a possible correlation with age.

Keywords: lyman-alpha galaxies; strong gravitational lensing; high-redshift galaxies; spectral energy distribution
On the Mass Function of GWTC-2 Binary Black Hole Systems and Their Progenitors

The distribution of LIGO black hole binaries (BBH) shows an intermediate-mass range consistent with the Salpeter initial mass function (IMF) in black hole formation by core-collapse supernovae, subject to preserving binary association. They are effectively parameterized by the mean mass μ with a Pearson correlation coefficient of r = 0.93 ± 0.06 of secondary to primary masses with a mean mass ratio of $\bar{q}\simeq 0.67$ , q = M 2/M 1, consistent with the paucity of intermediate-mass X-ray binaries. The mass function of LIGO BBHs is well approximated by a broken power law with a tail μ ≳ 31.4 M ⊙ in the mean binary mass $\mu =\left({M}_{1}+{M}_{2}\right)/2$ . Its power-law index of α B,true = 4.77 ± 0.73 inferred from the tail of the observed mass function is found to approach the upper bound 2α S = 4.7 of the uncorrelated binary IMF, defined by the Salpeter index α S = 2.35 of the IMF of stars. The observed low scatter in BBH mass ratio q evidences equalizing mass transfer in binary evolution prior to BBH formation. At the progenitor redshift ${z}^{{\prime} }$ , furthermore, the power-law index satisfies ${\alpha }_{B}^{{\prime} }\gt {\alpha }_{B}$ in a flat ΛCDM background cosmology. The bound ${\alpha }_{B,\mathrm{true}}^{{\prime} }\lesssim 2{\alpha }_{S}$ hereby precludes early formation at arbitrarily high redshifts ${z}^{{\prime} }\gg 1$ , which may be made more precise and robust with extended BBH surveys from upcoming LIGO O4-5 observations.

Keywords: astrophysical black holes
Emission Signatures from Subparsec Binary Supermassive Black Holes. III. Comparison of Models with Observations

We present a method for comparing the Hβ emission-line profiles of observed supermassive black hole (SBHB) candidates and models of subparsec SBHBs in circumbinary disks. Using the approach based on principal component analysis, we infer the values of the binary parameters for the spectroscopic SBHB candidates and evaluate the parameter degeneracies, representative of the uncertainties intrinsic to such measurements. We find that as a population, the SBHB candidates favor the average value of the semimajor axis corresponding to log(a/M) ≈ 4.20 ± 0.42 and comparable mass ratios, q > 0.5. If the SBHB candidates considered are true binaries, this result would suggest that there is a physical process that allows initially unequal-mass systems to evolve toward comparable mass ratios (e.g., accretion that occurs preferentially onto the smaller of the black holes) or point to some, yet unspecified, selection bias. Our method also indicates that the SBHB candidates equally favor configurations in which the mini-disks are coplanar or misaligned with the binary orbital plane. If confirmed for true SBHBs, this finding would indicate the presence of a physical mechanism that maintains misalignment of the mini-disks down to subparsec binary separations (e.g., precession driven by gravitational torques). The probability distributions of the SBHB parameters inferred for the observed SBHB candidates and our control group of AGNs are statistically indistinguishable, implying that this method can in principle be used to interpret the observed emission-line profiles once a sample of confirmed SBHBs is available but cannot be used as a conclusive test of binarity.

Keywords: astronomy data modeling; supermassive black holes; galaxy nuclei; active galaxies; galaxy mergers