adsabs/SciX_UAT_keywords huggingface dataset:
Fast Outflows and Luminous He II Emission in Dwarf Galaxies with Active Galactic Nuclei (AGN)

While stellar processes are believed to be the main source of feedback in dwarf galaxies, the accumulating discoveries of active galactic nuclei (AGN) in dwarf galaxies over recent years arouse the interest to also consider AGN feedback in them. Fast, AGN-driven outflows, a major mechanism of AGN feedback, have indeed been discovered in dwarf galaxies and may be powerful enough to provide feedback to their dwarf hosts. In this paper, we search for outflows traced by the blueshifted ultraviolet absorption features in three dwarf galaxies with AGN from the sample examined in our previous ground-based study. We confirm outflows traced by blueshifted absorption features in two objects and tentatively detect an outflow in the third object. In one object where the outflow is clearly detected in multiple species, photoionization modeling suggests that this outflow is located ∼0.5 kpc from the AGN, implying a galactic-scale impact. This outflow is much faster and possesses a higher kinetic energy outflow rate than starburst-driven outflows in sources with similar star formation rates, and is likely energetic enough to provide negative feedback to its host galaxy as predicted by simulations. Much broader (∼4000 km s‑1) absorption features are also discovered in this object, which may have the same origin as that of broad absorption lines in quasars. Additionally, strong He II λ1640 emission is detected in both objects where the transition falls in the wavelength coverage and is consistent with an AGN origin. In one of these two objects, a blueshifted He II λ1640 emission line is clearly detected, likely tracing a highly ionized AGN wind.

Keywords: agn host galaxies; dwarf galaxies; galactic winds; ultraviolet spectroscopy
Can Cuspy Dark-matter-dominated Halos Hold Cored Stellar Mass Distributions?

According to the current concordance cosmological model, dark matter (DM) particles are collisionless and produce self-gravitating structures with a central cusp, which, generally, is not observed. The observed density tends to a central plateau or core, explained within the cosmological model through the gravitational feedback of baryons on DM. This mechanism becomes inefficient when decreasing the galaxy's stellar mass so that in the low-mass regime (M ⋆ ≪ 106 M ⊙) the energy provided by the baryons is insufficient to modify cusps into cores. Thus, if cores exist in these galaxies they have to reflect departures from the collisionless nature of DM. Measuring the DM mass distribution in these faint galaxies is extremely challenging; however, their stellar mass distribution can be characterized through deep photometry. Here we provide a way of using only the stellar mass distribution to constrain the underlying DM distribution. The so-called Eddington inversion method allows us to discard pairs of stellar distributions and DM potentials requiring (unphysical) negative distribution functions in the phase space. In particular, cored stellar density profiles are incompatible with the Navarro-Frenk-White (NFW) potential expected from collisionless DM if the velocity distribution is isotropic and the system spherically symmetric. Through a case-by-case analysis, we are able to relax these assumptions to consider anisotropic velocity distributions and systems that do not have exact cores. In general, stellar distributions with radially biased orbits are difficult to reconcile with NFW-like potentials, and cores in the baryon distribution tend to require cores in the DM distribution.

Keywords: cold dark matter; dwarf galaxies; galaxy mass distribution; navarro-frenk-white profile; galaxy dark matter halos; low surface brightness galaxies; theoretical techniques
Serendipitous Discovery of Three Millisecond Pulsars with the GMRT in Fermi-directed Survey and Follow-up Radio Timing

We report the discovery of three millisecond pulsars (MSPs): PSRs J1120-3618, J1646-2142, and J1828+0625 with the Giant Metrewave Radio Telescope (GMRT) at a frequency of 322 MHz using a 32 MHz observing bandwidth. These sources were discovered serendipitously while conducting the deep observations to search for millisecond radio pulsations in the directions of unidentified Fermi Large Area Telescope (LAT) γ-ray sources. We also present phase coherent timing models for these MSPs using ~5 yr of observations with the GMRT. PSR J1120-3618 has a 5.5 ms spin period and is in a binary system with an orbital period of 5.6 days and minimum companion mass of 0.18 M ⊙, PSR J1646-2142 is an isolated object with a spin period of 5.8 ms, and PSR J1828+0625 has a spin period of 3.6 ms and is in a binary system with an orbital period of 77.9 days and minimum companion mass of 0.27 M ⊙. The two binaries have very low orbital eccentricities, in agreement with expectations for MSP-helium white dwarf systems. Using the GMRT 607 MHz receivers having a 32 MHz bandwidth, we have also detected PSR J1646-2142 and PSR J1828+0625, but not PSR J1120-3618. PSR J1646-2142 has a wide profile, with significant evolution between 322 and 607 MHz, whereas PSR J1120-3618 exhibits a single peaked profile at 322 MHz and PSR J1828+0625 exhibits a single peaked profile at both the observing frequencies. These MSPs do not have γ-ray counterparts, indicating that these are not associated with the target Fermi LAT pointing emphasizing the significance of deep blind searches for MSPs.

Keywords: millisecond pulsars; radio astronomy
Extreme Variability of the V488 Persei Debris Disk

V488 Persei is the most extreme debris disk known in terms of the fraction of the stellar luminosity it intercepts and reradiates. The infrared output of its disk is extremely variable, similar in this respect to the most variable disk known previously, that around ID8 in NGC 2547. We show that the variations are likely to be due to collisions of large planetesimals (≳100 km in diameter) in a belt being stirred gravitationally by a planetary or low-mass-brown-dwarf member of a planetary system around the star. The dust being produced by the resulting collisions is falling into the star due to drag by the stellar wind. The indicated planetesimal destruction rate is so high that it is unlikely that the current level of activity can persist for much longer than ~1000-10,000 yr and it may signal a major realignment of the configuration of the planetary system.

Keywords: debris disks; exoplanet migration
Improving NASA/IPAC Extragalactic Database Redshift Calculations

The NASA/IPAC Extragalactic Database (NED) is an impressive tool for finding near-exhaustive information on millions of astrophysical objects. Here, we outline a small systematic error that occurs in NED because a low-redshift approximation is used when making the correction from redshifts in the heliocentric frame to the cosmic microwave background (CMB) rest frame. It means that historically NED systematically misreported the values of CMB-frame redshifts by up to ~10-3z (about 0.001 at redshift of 1). This is a systematic error, and therefore the impact on applications requiring precise redshifts has the potential to be significant-for example, a systematic redshift error of ~10-4 at low redshift could resolve the Hubble tension. We have consulted with the NED team and they are updating the software to remove this systematic error so these corrections are accurate at all redshifts. Here, we explain the changes and how they impact the redshift values NED currently reports.

Keywords: galaxies; astronomy databases; cosmology
Luminous Lyα Emitters with Very Blue UV-continuum Slopes at Redshift 5.7 ≤ z ≤ 6.6

We study six luminous Lyα emitters (LAEs) with very blue rest-frame UV continua at 5.7 ≤ z ≤ 6.6. These LAEs have previous Hubble Space Telescope (HST) and Spitzer IRAC observations. Combining our newly acquired HST images, we find that their UV-continuum slopes β are in a range of -3.4 ≤ β ≤ -2.6. Unlike previous, tentative detections of β ≃ -3 in photometrically selected, low-luminosity galaxies, our LAEs are spectroscopically confirmed and luminous (MUV < -20 mag). We model their broadband spectral energy distributions (SEDs), and find that two β ≃ -2.6 ± 0.2 galaxies can be well fitted with young and dust-free stellar populations. However, it becomes increasingly difficult to fit bluer galaxies. We explore further interpretations by including the non-zero LyC escape fraction fesc, very low metallicities, and/or active galactic nucleus contributions. Assuming fesc ≃ 0.2, we achieve the bluest slopes β ≃ -2.7 when nebular emission is considered. This can nearly explain the SEDs of two galaxies with β ≃ -2.8 and -2.9 (σβ = 0.15). Larger fesc values and very low metallicities are not favored by the strong nebular line emission (evidenced by the IRAC flux) or the observed (IRAC 1 - IRAC 2) color. Finally, we find that the β ≃ -2.9 galaxy can potentially be well explained by the combination of a very young population with a high fesc (≥0.5) and an old, dusty population. We are not able to produce two β ≃ -3.4 ± 0.4 galaxies. Future deep spectroscopic observations are needed to fully understand these galaxies.

Keywords: high-redshift galaxies; lyman-alpha galaxies; galaxy properties
The Complete Redshift Distribution of Dusty Star-forming Galaxies from the SPT-SZ Survey

The South Pole Telescope (SPT) has systematically identified 81 high-redshift, strongly gravitationally lensed, dusty star-forming galaxies (DSFGs) in a 2500 square degree cosmological millimeter-wave survey. We present the final spectroscopic redshift survey of this flux-limited (S870 μm > 25 mJy) sample, initially selected at 1.4 mm. The redshift survey was conducted with the Atacama Large Millimeter/submillimeter Array across the 3 mm spectral window, targeting carbon monoxide line emission. By combining these measurements with ancillary data, the SPT sample is now spectroscopically complete, with redshifts spanning 1.9 < z < 6.9 and a median of $z=3.9\pm 0.2$ . We present the millimeter through far-infrared photometry and spectral energy density fits for all sources, along with their inferred intrinsic properties. Comparing the properties of the SPT sources to the unlensed DSFG population, we demonstrate that the SPT-selected DSFGs represent the most extreme infrared-luminous galaxies, even after accounting for strong gravitational lensing. The SPT sources have a median star formation rate of $2.3(2)\times {10}^{3}{M}_{\odot }\,\,{\mathrm{yr}}^{-1}$ and a median dust mass of $1.4(1)\times {10}^{9}{M}_{\odot }$ . However, the inferred gas depletion timescales of the SPT sources are comparable to those of unlensed DSFGs, once redshift is taken into account. This SPT sample contains roughly half of the known spectroscopically confirmed DSFGs at z > 5, making this the largest sample of high-redshift DSFGs to date, and enabling the "high-redshift tail" of extremely luminous DSFGs to be measured. Though galaxy formation models struggle to account for the SPT redshift distribution, the larger sample statistics from this complete and well-defined survey will help inform future theoretical efforts.

Keywords: observational cosmology; early universe; high-redshift galaxies; galaxy evolution; interstellar molecules
Two Portions of the Sagittarius Stream in the LAMOST Complete Spectroscopic Survey of Pointing Area at the Southern Galactic Cap

We constructed a sample of 13,798 stars with Teff, log g, [Fe/H], radial velocity, proper motions, and parallaxes from LAMOST DR5 and Gaia DR2 in the LAMOST Complete Spectroscopic Survey of Pointing Area (LaCoSSPAr) at the Southern Galactic Cap consisting of areas A and B. Using the distributions in both proper motions and radial velocity, we detected very significant overdensities in these two areas. These substructures most likely are portions of the Sagittarius (Sgr) stream. With the Density-Based Spatial Clustering of Applications with Noise (DBSCAN) algorithm, 220 candidates stream members were identified. Based upon distance to the Sun and published models, 106 of these stars are likely to be the members of the Sgr stream. The abundance pattern of these members using [α/Fe] from Xiang et al. were found to be similar to Galactic field stars with [Fe/H] < -1.5 and deficient to Milky Way populations at similar metallicities with [Fe/H] > -1.0. No vertical and only small radial gradients in metallicity along the orbit of the Sgr stream were found in our Sgr stream candidates.

Keywords: stellar abundances; galaxy kinematics
The Hubble PanCET Program: Emission Spectrum of Hot Jupiter HAT-P-41b

We present the most complete emission spectrum for inflated hot Jupiter HAT-P-41b combining new Hubble Space Telescope Wide Field Camera/G141 spectrum from the Hubble Panchromatic Comparative Exoplanet Treasury program with archival Spitzer eclipse observations. We found a near blackbody-like emission spectrum, which is best fitted with an isothermal temperature-pressure (TP) profile, that agrees well with the dayside heat redistribution scenario assuming zero Bond albedo. The noninverted TP profile is consistent with the nondetection of near-UV/optical absorbers in the transit spectra. We do not find any evidence for significant H- opacity nor a metal-rich atmosphere. HAT-P-41b is an ideal target that sits in the transitioning parameter space between hot and ultra-hot Jupiters, and future James Webb Space Telescope observations will help us to better constrain the thermal structure and chemical composition.

Keywords: exoplanet atmospheres
Constraining the Kilonova Rate with Zwicky Transient Facility Searches Independent of Gravitational Wave and Short Gamma-Ray Burst Triggers

The first binary neutron star merger, GW170817, was accompanied by a radioactivity-powered optical/infrared transient called a kilonova. To date, no compelling kilonova has been found in all-sky optical surveys, independently of short gamma-ray burst and gravitational-wave triggers. In this work, we searched the first 23 months of the Zwicky Transient Facility (ZTF) data stream for candidate kilonovae in the form of rapidly evolving transients. We combined ZTF alert queries with forced point-spread-function photometry and nightly flux stacking to increase our sensitivity to faint and fast transients. Automatic queries yielded >11,200 candidates, 24 of which passed quality checks and selection criteria based on a grid of kilonova models tailored for both binary neutron star and neutron star-black hole mergers. None of the candidates in our sample was deemed a possible kilonova after thorough vetting. The sources that passed our selection criteria are dominated by Galactic cataclysmic variables. We identified two fast transients at high Galactic latitude, one of which is the confirmed afterglow of long-duration GRB 190106A, the other is a possible cosmological afterglow. Using a survey simulation code, we constrained the kilonova rate for a range of models including top-hat, linearly decaying light curves, and synthetic light curves obtained with radiative transfer simulations. For prototypical GW170817-like kilonovae, we constrain the rate to be $R\lt 1775$ Gpc-3 yr-1 (95% confidence). By assuming a population of kilonovae with the same geometry and composition of GW170817 observed under a uniform viewing angle distribution, we obtained a constraint on the rate of R < 4029 Gpc-3 yr-1.

Keywords: neutron stars; compact objects; gravitational wave sources; transient sources; surveys; r-process; optical observation; optical bursts; gamma-ray bursts; cataclysmic variable stars; gravitational wave astronomy
Switchbacks and Associated Magnetic Holes Observed near the Alfvén Critical Surface

During recent solar encounters, the Parker Solar Probe (PSP) began its initial dips below the Alfvén critical surface to measure in situ the sub-Alfvénic coronal wind. While the near-Sun super-Alfvénic solar wind is shown to be dominated by impulsive magnetic switchbacks (short magnetic field reversals), these brief encounters with the sub-Alfvénic coronal wind show switchbacks and associated magnetic holes (MHs) to still be present but different in character. In this work, we compare and contrast specific features of the switchbacks, including the change in B r and V r and associated boundary B-field dropouts (MHs) at locations when PSP was both above and below the Alfvén critical surface. We use observations from the PSP perihelion Encounters 8 (E8) and 12 (E12) in the analysis. We first perform a superposed epoch analysis to identify common features in the switchback boundaries, including the formation of the associated ∣B∣ dropouts/MHs in slow and fast flows. We then examine the presence of B-field dropouts/MHs as a function of Alfvén Mach number, M A. From E12, we find that the switchbacks have a systematic reduction in rotation (and reduction in B r deflection) with decreasing M A. Further, the ∣B∣ dropouts/MHs associated with the boundaries were also found to decrease in strength and occurrence with M A (with no or few ∣B∣ dropouts at M A < 0.7). The results suggest that the switchback rotation and boundary-associated MHs are connected, possibly consistent with diamagnetic effects at the boundary that require large rotations to be initiated.

Keywords: solar magnetic fields; plasma physics; solar wind
A Possible Meteoric Fall in Cabeza la Vaca (Spain) in 1970 January

We recover a report in the "HOY" regional newspaper about a presumed meteorite fall near Cabeza la Vaca, Spain. The report details observable effects like a crater, uprooted tree, and a destroyed fence. While the exact date is unknown, it likely occurred within a week of 1970 January 27. The report lacks the crater size specification. This research note underscores the potential significance of the reported meteorite fall, encouraging further investigation.

Keywords: meteorites
Planetesimals on Eccentric Orbits Erode Rapidly

We investigate the possibility of erosion of planetesimals in a protoplanetary disk. We use theory and direct numerical simulations (lattice Boltzmann method) to calculate the erosion of large-much larger than the mean-free path of gas molecules-bodies of different shapes in flows. We find that erosion follows a universal power law in time, at intermediate times, independent of the Reynolds number of the flow and the initial shape of the body. Consequently, we estimate that planetesimals in eccentric orbits, of even very small eccentricity, rapidly (in about 100 yr) erodes away if the semimajor axis of their orbit lies in the inner disk-less than about 10 au. Even planetesimals in circular orbits erode away in approximately 10,000 yr if the semimajor axis of their orbits are ⪅0.6 au.

Keywords: planet formation; protoplanetary disks
On the Production of He+ of Solar Origin in the Solar Wind

Solar wind measurements in the heliosphere predominantly comprise protons, alphas, and minor elements in a highly ionized state. The majority of low-charge states, such as He+, measured in situ are often attributed to pick-up ions of nonsolar origin. However, through inspection of the velocity distribution functions of near-Earth measurements, we find a small but significant population of He+ ions in the normal solar wind whose properties indicate that it originated from the Sun and has evolved as part of the normal solar wind. Current ionization models, largely governed by electron impact and radiative ionization and recombination processes, underestimate this population by several orders of magnitude. Therefore, to reconcile the singly ionized He observed, we investigate the recombination of solar He2+ through charge exchange with neutrals from circumsolar dust as a possible formation mechanism of solar He+. We present an empirical profile of neutrals necessary for charge exchange to become an effective vehicle to recombine He2+ to He+ such that it meets observational He+ values. We find that the formation of He+ is not only sensitive to the density of neutrals but also to the inner boundary of the neutral distribution encountered along the solar wind path. However, further observational constraints are necessary to confirm that the interaction between solar α particles and dust neutrals is the primary source of the He+ observations.

Keywords: solar wind; interplanetary dust; charge exchange recombination
Dynamics of Star Cluster Formation: Mergers in Gas-rich Environments

We perform high-resolution simulations of forming star clusters as they merge inside giant molecular clouds (GMCs) using hydrodynamics coupled to N-body dynamics to simultaneously model both the gas and stars. We zoom in to previously run GMC simulations and resolve clusters into their stellar and gas components while including the surrounding GMC environment. We find that GMC gas is important in facilitating the growth of clusters in their embedded phase by promoting cluster mergers. Mergers induce asymmetric expansion of the stellar component of the clusters in our simulations. As well, mergers induce angular momentum in the clusters' stellar and gas components. We find that mergers can lead to an increase in the amount of dense gas present in clusters if a background gas distribution is present. We predict that this can lead to new star formation that can change the overall distribution of cluster stars in velocity space. Our results suggest that subcluster mergers in the presence of background gas can imprint dynamical signatures that can be used to constrain cluster formation histories.

Keywords: star clusters; stellar dynamics; stellar kinematics; star formation
Integrated Geostationary Solar Energetic Particle Events Catalog: GSEP

We present a catalog of solar energetic particle (SEP) events covering solar cycles 22, 23 and 24. We correlate and integrate three existing catalogs based on Geostationary Operational Environmental Satellite integral proton flux data. We visually verified and labeled each event in the catalog to provide a homogenized data set. We have identified a total of 341 SEP events of which 245 cross the Space Weather Prediction Center threshold of a significant proton event. The metadata consists of physical parameters and observables concerning the possible source solar eruptions, namely flares and coronal mass ejections for each event. The sliced time-series data of each event, along with intensity profiles of proton fluxes in several energy bands, have been made publicly available. This data set enables researchers in machine learning and statistical analysis to understand the SEPs and the source eruption characteristics useful for space weather prediction.

Keywords: solar energetic particles
Decayless Oscillations in Solar Coronal Bright Points

Decayless kink oscillations of solar coronal loops (or decayless oscillations for short) have attracted great attention since their discovery. Coronal bright points (CBPs) are mini-active regions and consist of loops with a small size. However, decayless oscillations in CBPs have not been widely reported. In this study, we identified this kind of oscillations in some CBPs using 171 Å images taken by the Atmospheric Imaging Assembly on board the Solar Dynamics Observatory. After using the motion magnification algorithm to increase oscillation amplitudes, we made time-distance maps to identify the oscillatory signals. We also estimated the loop lengths and velocity amplitudes. We analyzed 23 CBPs and found 31 oscillation events in 16 of them. The oscillation periods range from 1 to 8 minutes (on average about 5 minutes), and the displacement amplitudes have an average value of 0.07 Mm. The average loop length and velocity amplitude are 23 Mm and 1.57 km s-1, respectively. Relationships between different oscillation parameters are also examined. Additionally, we performed a simple model to illustrate how these subpixel oscillation amplitudes (less than 0.4 Mm) could be detected. Results of the model confirm the reliability of our data processing methods. Our study shows for the first time that decayless oscillations are common in small-scale loops of CBPs. These oscillations allow for seismological diagnostics of the Alfvén speed and magnetic field strength in the corona.

Keywords: solar oscillations; quiet solar corona; solar coronal seismology