adsabs/SciX_UAT_keywords huggingface dataset:
New Constraints on the Dark Matter Density Profiles of Dwarf Galaxies from Proper Motions of Globular Cluster Streams

The central density profiles in dwarf galaxy halos depend strongly on the nature of dark matter (DM). Recently, in Malhan et al. we employed N-body simulations to show that the cuspy cold DM subhalos predicted by cosmological simulations can be differentiated from cored subhalos using the properties of accreted globular cluster (GC) streams since these GCs experience tidal stripping within their parent halos prior to accretion onto the Milky Way. We previously found that clusters that are accreted within cuspy subhalos produce streams with larger physical widths and higher dispersions in line-of-sight velocity and angular momentum than streams that are accreted within cored subhalos. Here, we use the same suite of simulations to demonstrate that the dispersion in the tangential velocities of streams ( ${\sigma }_{{v}_{\mathrm{Tan}}}$ ) is also sensitive to the central DM density profiles of their parent dwarfs and GCs that they were accreted from; cuspy subhalos produce streams with larger ${\sigma }_{{v}_{\mathrm{Tan}}}$ than those accreted inside cored subhalos. Using Gaia EDR3 observations of multiple GC streams we compare their ${\sigma }_{{v}_{\mathrm{Tan}}}$ values with simulations. The measured ${\sigma }_{{v}_{\mathrm{Tan}}}$ values are consistent with both an "in situ" origin and with accretion inside cored subhalos of M ~ 108-9 M ⊙ (or very low-mass cuspy subhalos of mass ~108 M ⊙). Despite the large current uncertainties in ${\sigma }_{{v}_{\mathrm{Tan}}}$ , we find a low probability that any of the progenitor GCs were accreted from cuspy subhalos of M ≳ 10 9 M ⊙. The uncertainties on Gaia tangential velocity measurements are expected to decrease in future and will allow for stronger constraints on subhalo DM density profiles.

Keywords: stellar streams; surveys; dark matter; dwarf galaxies; milky way galaxy; globular star clusters
The MOSDEF Survey: Kinematic and Structural Evolution of Star-forming Galaxies at 1.4 ≤ z ≤ 3.8

We present ionized gas kinematics for 681 galaxies at $z\sim 1.4\mbox{--}3.8$ from the MOSFIRE Deep Evolution Field survey, measured using models that account for random galaxy-slit misalignments together with structural parameters derived from CANDELS Hubble Space Telescope (HST) imaging. Kinematics and sizes are used to derive dynamical masses. Baryonic masses are estimated from stellar masses and inferred gas masses from dust-corrected star formation rates (SFRs) and the Kennicutt-Schmidt relation. We measure resolved rotation for 105 galaxies. For the remaining 576 galaxies we use models based on HST imaging structural parameters together with integrated velocity dispersions and baryonic masses to statistically constrain the median ratio of intrinsic ordered to disordered motion, $V/{\sigma }_{V,0}$ . We find that $V/{\sigma }_{V,0}$ increases with increasing stellar mass and decreasing specific SFR (sSFR). These trends may reflect marginal disk stability, where systems with higher gas fractions have thicker disks. For galaxies with detected rotation we assess trends between their kinematics and mass, sSFR, and baryon surface density ( ${{\rm{\Sigma }}}_{\mathrm{bar},e}$). Intrinsic dispersion correlates most with ${{\rm{\Sigma }}}_{\mathrm{bar},e}$ , and velocity correlates most with mass. By comparing dynamical and baryonic masses, we find that galaxies at $z\sim 1.4\mbox{--}3.8$ are baryon dominated within their effective radii ( ${R}_{E}$), with ${M}_{\mathrm{dyn}}$ / ${M}_{\mathrm{baryon}}$ increasing over time. The inferred baryon fractions within ${R}_{E}$ , ${f}_{\mathrm{bar}}$ , decrease over time, even at fixed mass, size, or surface density. At fixed redshift, ${f}_{\mathrm{bar}}$ does not appear to vary with stellar mass but increases with decreasing ${R}_{E}$ and increasing ${{\rm{\Sigma }}}_{\mathrm{bar},e}$ . For galaxies at $z\gtrsim 2$ , the median inferred baryon fractions generally exceed 100%. We discuss possible explanations and future avenues to resolve this tension.

Keywords: galaxy kinematics; galaxy dynamics; high-redshift galaxies; galaxy evolution
Investigation of Profile Shifting and Subpulse Movement in PSR J0344-0901 with FAST

We report two phenomena detected in PSR J0344‑0901 from two observations conducted at frequencies centered at 1.25 GHz using the Five-hundred-meter Aperture Spherical Radio Telescope. The first phenomenon manifests as the pulse emission shifting to later longitudinal phases and then gradually returning to its original location. The event lasts for about 216 pulse periods, with an average shift of about 0.°7 measured at the peak of the integrated profile. Changes in the polarization position angle (PPA) are detected around the trailing edge of the profile, together with an increase in the profile width. The second phenomenon is characterized by the apparent movement of subpulses, which results in different subpulse track patterns across the profile window. For the first time in this pulsar, we identify four emission modes, each with unique subpulse movement, and determine the pattern periods for three of them. Pulse nulling was not detected. Modeling of the changes in the PPA using the rotating vector model gives an inclination angle of 75.°12 ± 3.°80 and an impact parameter of ‑3.°17 ± 5.°32 for this pulsar. We speculate that the subpulse movement may be related to the shifting of the pulse emission.

Keywords: radio pulsars
A Comparative Study of Long and Short GRBs. II. A Multiwavelength Method to Distinguish Type II (Massive Star) and Type I (Compact Star) GRBs

Gamma-ray bursts (GRBs) are empirically classified as long-duration GRBs (LGRBs, >2 s) and short-duration GRBs (SGRBs, <2 s). Physically they can be grouped into two distinct progenitor categories: those originating from collapse of massive stars (also known as Type II) and those related to mergers of compact stars (also known as Type I). Even though most LGRBs are Type II and most SGRBs are Type I, the duration criterion is not always reliable to determine the physical category of a certain GRB. Based on our previous comprehensive study of the multiwavelength properties of long and short GRBs, here we utilize the naive Bayes method to physically classify GRBs as Type I and Type II GRBs based on multiwavelength criteria. It results in a 0.5% training error rate and a 1% test error rate. Moreover, there is a gap [-1.2, -0.16] in the distribution of the posterior odds, $\mathrm{log}O(\mathrm{II}:{\rm{I}})$ , the Type II to Type I probability ratio. Therefore, we propose to use ${ \mathcal O }=\mathrm{log}O(\mathrm{II}:{\rm{I}})+0.7$ as the parameter to classify GRBs into Type I (<0) or Type II (>0). The only confirmed Type I GRB, GRB 170817A, has log $O(\mathrm{II}:{\rm{I}})=-10$ . According to this criterion, the supernova-less long GRBs 060614 and 060505 belong to Type I, and two controversial short GRBs 090426 and 060121 belong to Type II.

Keywords: gamma-ray bursts
The JWST Early Release Science Program for the Direct Imaging and Spectroscopy of Exoplanetary Systems

The direct characterization of exoplanetary systems with high-contrast imaging is among the highest priorities for the broader exoplanet community. As large space missions will be necessary for detecting and characterizing exo-Earth twins, developing the techniques and technology for direct imaging of exoplanets is a driving focus for the community. For the first time, JWST will directly observe extrasolar planets at mid-infrared wavelengths beyond 5 μm, deliver detailed spectroscopy revealing much more precise chemical abundances and atmospheric conditions, and provide sensitivity to analogs of our solar system ice-giant planets at wide orbital separations, an entirely new class of exoplanet. However, in order to maximize the scientific output over the lifetime of the mission, an exquisite understanding of the instrumental performance of JWST is needed as early in the mission as possible. In this paper, we describe our 55 hr Early Release Science Program that will utilize all four JWST instruments to extend the characterization of planetary-mass companions to ~15 μm as well as image a circumstellar disk in the mid-infrared with unprecedented sensitivity. Our program will also assess the performance of the observatory in the key modes expected to be commonly used for exoplanet direct imaging and spectroscopy, optimize data calibration and processing, and generate representative data sets that will enable a broad user base to effectively plan for general observing programs in future Cycles.

Keywords: coronagraphic imaging; direct imaging; exoplanet detection methods; space telescopes; exoplanet atmospheres
Electromagnetic Ion-Ion Instabilities in Space Plasmas: Effects of Suprathermal Populations

In collision-poor plasmas from space, three distinct ion-ion instabilities can be driven by the proton beams streaming along the background magnetic field: left-hand resonant, nonresonant, and right-hand resonant instabilities. These instabilities are in general investigated considering only idealized proton beams with Maxwellian velocity distributions, and ignoring the implications of suprathermal populations, usually reproduced by the Kappa power laws. Moreover, the existing theories minimize the kinetic effects of electrons, assuming them isotropic and Maxwellian distributed. In an attempt to overcome these limitations, in the present paper we present the results of an extended investigation of ion-ion instabilities, which show that their dispersion and stability properties (e.g., growth rates, wave frequencies, and the unstable wavenumbers) are highly sensitive to the influence of suprathermal populations and anisotropic electrons. These results offer valuable explanations for the origin of the enhanced low-frequency fluctuations, frequently observed in space plasmas and associated with proton beams.

Keywords: space plasmas; solar wind; shocks; interplanetary medium
First Observation of Kinetic Alfvén Waves behind Reconnection Front in Terrestrial Magnetotail

Reconnection fronts, also known as dipolarization fronts (DFs), and kinetic Alfvén waves (KAWs) are two of the widely observed structures and waves in the terrestrial magnetotail, but their correlation remains elusive in previous spacecraft measurements. Using high-resolution Magnetospheric Multiscale data, here we provide the first observational identification of KAWs behind the DF. These low-frequency dispersive KAWs propagate quasi-perpendicular to the magnetic field at phase speeds slower than local Alfvén speed, and are highly correlated with high-frequency whistlers propagating obliquely to the magnetic field. Specifically, whistlers appear at local magnetic field minima (wave troughs of KAWs) and disappear at local magnetic field maxima (wave crests of KAWs), highly consistent with the source region of whistler waves previously reported near equator and dayside magnetopause. Our study also suggests that the KAWs behind DFs could originate from the diffusion region of magnetic reconnection. These findings improve our understanding of the relationship between DFs, KAWs, and whistler waves in terrestrial magnetotail.

Keywords: alfven waves; space plasmas; plasma physics
Approximating Stellar Metallicity Using Photometric Machine Learning

Stellar metallicity is an important metric in analyzing stellar evolution. Measuring metallicity (e.g., [Fe/H]) usually requires spectroscopic data, but difficulties associated with gathering spectra for distant objects severely reduces the number of stars for which metallicity can be calculated. The Sloan Expedition for Galactic Understanding and Exploration (SEGUE) spectroscopic surveys are one of the most abundant public-sources of objects with spectra. Despite cataloging over 106 objects, the SEGUE data makes up only 0.4% of the data in SDSS photometric surveys. To overcome the limited spectra, this machine-learning method can approximate [Fe/H] from the 5 SDSS photometric filters with a root-mean-square-error (RMSE) of 0.277 dex. The RMSE from this method is similar to the scatter expected in [Fe/H] measurements from low-resolution spectra. Therefore, this method achieves similar accuracy to low-resolution spectra but can be applied to a few orders of magnitude more stars than what the current spectroscopic surveys allow.

Keywords: metallicity; photometric systems; stellar evolution; astronomy software; random forests
EUCLIA. II. On the Puzzling Large UV to X-Ray Lags in Seyfert Galaxies

Recent intense X-ray and UV monitoring campaigns with Swift have detected clear UV lags behind X-ray in several local active galactic nuclei (AGNs). The UV to X-ray lags are often larger (by a factor of up to ∼20) than expected if the UV variation is simply due to the X-ray reprocessing. We previously developed a model in which the UV/optical variations are attributed to disk turbulences, and the effect of large-scale turbulence is considered. Our model, which overcomes many severe challenges to the reprocessing scheme, can explain the observed variations in NGC 5548, particularly the correlations and lags among the UV/optical bands. In this work, assuming the corona heating is associated with turbulences in the inner accretion disk, we extend our study to model the correlations and lags between the X-ray and UV/optical bands. We find that our model, without the need of light echoing, can well reproduce the observed UV to X-ray lags and the optical to UV lags simultaneously in four local Seyfert galaxies, including NGC 4151, NGC 4395, NGC 4593, and NGC 5548. In our scenario, relatively larger UV to X-ray lag is expected for AGN with smaller innermost disk radius and thus more compact corona. Interestingly, for these Seyfert galaxies studied in this work, sources with relatively larger UV to X-ray lags do have broader Fe Kα lines, indicative of relativistic broadening due to more compact corona and smaller innermost disk radius. If confirmed with more X-ray and UV monitoring campaigns, this interesting discovery would provide a new probe to the inner disk/corona.

Keywords: galaxy nuclei; seyfert galaxies; accretion; active galactic nuclei
Non-detection of M60-UCD1 in Quasi-simultaneous X-Ray and Radio Observations

Simultaneous detection in X-rays and radio, following the proportionality implied by the "fundamental plane of black hole activity," can indicate the presence of an accreting black hole (BH), allowing a rough estimate of its mass. We used the XMM-Newton satellite and the Karl G. Jansky Very Large Array to perform quasi-simultaneous observations (within 24 hr) of the ultra-compact dwarf galaxy M60-UCD1, where the presence of a supermassive BH was inferred from stellar dynamics. The galaxy was not detected in either the X-ray or the radio band. We used the fundamental plane of BH activity to set constraints on the mass of any BH that might reside in its nucleus.

Keywords: galaxies; ultracompact dwarf galaxies; astrophysical black holes
On Encounter Rates in Star Clusters

Close encounters between stars in star-forming regions are important as they can perturb or destroy protoplanetary disks, young planetary systems, and multiple-star systems. We simulate simple, virialized, equal-mass N-body star clusters and find that both the rate and the total number of encounters between stars vary by factors of several in statistically identical clusters due to the stochastic/chaotic details of the orbits and stellar dynamics. Encounters tend to "saturate" rapidly in the core of a cluster, with stars there each having many encounters, while more distant stars have none. However, we find that the fraction of stars that has had at least one encounter within a particular distance grows in the same way (scaling with the crossing time and half-mass radius) in all clusters, and we present a new (empirical) way of estimating the fraction of stars that has had at least one encounter at a particular distance.

Keywords: star clusters; circumstellar disks; n-body simulations; gravitational interaction
Two-dimensional Configuration and Temporal Evolution of Spark Discharges in Pulsars

We report on our investigation of the evolution of a system of spark discharges in the inner acceleration region (IAR) above the pulsar polar cap. The surface of the polar cap is heated to temperatures of around 106 K and forms a partially screened gap (PSG), due to thermionic emission of positively charged ions from the stellar surface. The spark lags behind corotation speed during their lifetimes due to variable E × B drift. In a PSG, spark discharges arise in locations where the surface temperatures go below the critical level (T i ) for ions to freely flow from the surface. The spark commences due to the large drop in potential developing along the magnetic field lines in these lower temperature regions and subsequently back-streaming particles heat the surface to T i . Regulation of the temperature requires the polar cap to be tightly filled with sparks and a continuous presence of sparks is required around its boundary since no heating is possible from the closed field line region. We estimate the time evolution of the spark system in the IAR, which shows a gradual shift in the spark formation along two distinct directions resembling clockwise and anticlockwise motions in two halves of the polar cap. Due to the differential shift of the spark pattern in the two halves, a central spark develops representing the core emission. The temporal evolution of the spark process was simulated for different orientations of a non-dipolar polar cap and reproduced the diverse observational features associated with subpulse drifting.

Keywords: radio pulsars; pulsars
Gamma-Ray Burst Constraints on Cosmological Models from the Improved Amati Correlation

An improved Amati correlation was constructed in ApJ 931 (2022) 50 by us recently. In this paper, we further study constraints on the ΛCDM and wCDM models from the gamma-ray bursts (GRBs) standardized with the standard and improved Amati correlations, respectively. By using the Pantheon Type Ia supernova sample to calibrate the latest A220 GRB data set, the GRB Hubble diagram is obtained model-independently. We find that at the high-redshift region (z > 1.4) the GRB distance modulus from the improved Amati correlation is larger apparently than that from the standard Amati one. The GRB data from the standard Amati correlation only give a lower bound limit on the present matter density parameter Ωm0, while the GRBs from the improved Amati correlation constrain the Ωm0 with the 68% confidence level to be ${0.308}_{-0.230}^{+0.066}$ and ${0.307}_{-0.290}^{+0.057}$ in the ΛCDM and wCDM models, respectively, which are very consistent with those given by other current popular observational data including baryon acoustic oscillation, cosmic microwave background (CMB) radiation, and so on. Once the H(z) data are added in our analysis, the constraint on the Hubble constant H 0 can be achieved. We find that two different correlations provide slightly different H 0 results but the marginalized mean values seem to be close to that from the Planck 2018 CMB radiation observations.

Keywords: cosmological parameters
The Interaction between AGN and Starburst Activity in the Circumnuclear Region of NGC 7469 as Viewed with JWST

We combine mid-infrared diagnostics obtained from integral-field-unit observations taken with Mid-Infrared Instrument/Medium Resolution Spectrograph on the James Webb Space Telescope with cold molecular gas information derived from Atacama Large Millimeter/submillimeter Array observations of CO(1-0) emission to investigate the star formation rate and efficiency within the central ~1.5 kpc × 1.3 kpc region of the Seyfert 1 galaxy NGC 7469 on ~100 pc scales. The active nucleus leaves a notable imprint on its immediate surroundings by elevating the temperature of the warm molecular gas, driving an ionized gas outflow on subkiloparsec scales, and selectively destroying small dust grains. These effects, nevertheless, have relatively little impact on the cold circumnuclear medium or its ability to form stars. Most of the star formation in NGC 7469 is confined to a clumpy starburst ring, but the star formation efficiency remains quite elevated even for the nuclear region that is most affected by the active nucleus.

Keywords: star formation; active galaxies; molecular gas; starburst galaxies; luminous infrared galaxies
Deflating Super-puffs: Impact of Photochemical Hazes on the Observed Mass-Radius Relationship of Low-mass Planets

The observed mass-radius relationship of low-mass planets informs our understanding of their composition and evolution. Recent discoveries of low-mass, large-radius objects ("super-puffs") have challenged theories of planet formation and atmospheric loss, as their high inferred gas masses make them vulnerable to runaway accretion and hydrodynamic escape. Here we propose that high-altitude photochemical hazes could enhance the observed radii of low-mass planets and explain the nature of super-puffs. We construct model atmospheres in radiative-convective equilibrium and compute rates of atmospheric escape and haze distributions, taking into account haze coagulation, sedimentation, diffusion, and advection by an outflow wind. We develop mass-radius diagrams that include atmospheric lifetimes and haze opacity, which is enhanced by the outflow, such that young (∼0.1-1 Gyr), warm (Teq ≥ 500 K), low-mass objects (Mc < 4 M⊕) should experience the most apparent radius enhancement due to hazes, reaching factors of three. This reconciles the densities and ages of the most extreme super-puffs. For Kepler-51b, the inclusion of hazes reduces its inferred gas mass fraction to <10%, similar to that of planets on the large-radius side of the sub-Neptune radius gap. This suggests that Kepler-51b may be evolving toward that population and that some warm sub-Neptunes may have evolved from super-puffs. Hazes also render transmission spectra of super-puffs and sub-Neptunes featureless, consistent with recent measurements. Our hypothesis can be tested by future observations of super-puffs' transmission spectra at mid-infrared wavelengths, where we predict that the planet radius will be half of that observed in the near-infrared.

Keywords: exoplanet atmospheres; exoplanet structure; exoplanet atmospheric composition; exoplanet evolution; exoplanet astronomy; exoplanets
CMZoom: Survey Overview and First Data Release

We present an overview of the CMZoom survey and its first data release. CMZoom is the first blind, high-resolution survey of the Central Molecular Zone (CMZ; the inner 500 pc of the Milky Way) at wavelengths sensitive to the pre-cursors of high-mass stars. CMZoom is a 550 hr Large Program on the Submillimeter Array that mapped at 1.3 mm all of the gas and dust in the CMZ above a molecular hydrogen column density of 1023 cm-2 at a resolution of ∼3″ (0.1 pc). In this paper, we focus on the 1.3 mm dust continuum and its data release, but also describe CMZoom spectral line data which will be released in a forthcoming publication. While CMZoom detected many regions with rich and complex substructure, its key result is an overall deficit in compact substructures on 0.1-2 pc scales (the compact dense gas fraction: CDGF). In comparison with clouds in the Galactic disk, the CDGF in the CMZ is substantially lower, despite having much higher average column densities. CMZ clouds with high CDGFs are well-known sites of active star formation. The inability of most gas in the CMZ to form compact substructures is likely responsible for the dearth of star formation in the CMZ, surprising considering its high density. The factors responsible for the low CDGF are not yet understood but are plausibly due to the extreme environment of the CMZ, having far-reaching ramifications for our understanding of the star formation process across the cosmos.

Keywords: star formation; galactic center; submillimeter astronomy; dense interstellar clouds; molecular clouds; infrared dark clouds; protostars; interferometry