adsabs/SciX_UAT_keywords huggingface dataset:
PHANGS-JWST First Results: Spurring on Star Formation: JWST Reveals Localized Star Formation in a Spiral Arm Spur of NGC 628

We combine JWST observations with Atacama Large Millimeter/submillimeter Array CO and Very Large Telescope MUSE Hα data to examine off-spiral arm star formation in the face-on, grand-design spiral galaxy NGC 628. We focus on the northern spiral arm, around a galactocentric radius of 3-4 kpc, and study two spurs. These form an interesting contrast, as one is CO-rich and one CO-poor, and they have a maximum azimuthal offset in MIRI 21 μm and MUSE Hα of around 40° (CO-rich) and 55° (CO-poor) from the spiral arm. The star formation rate is higher in the regions of the spurs near spiral arms, but the star formation efficiency appears relatively constant. Given the spiral pattern speed and rotation curve of this galaxy and assuming material exiting the arms undergoes purely circular motion, these offsets would be reached in 100-150 Myr, significantly longer than the 21 μm and Hα star formation timescales (both < 10 Myr). The invariance of the star formation efficiency in the spurs versus the spiral arms indicates massive star formation is not only triggered in spiral arms, and cannot simply occur in the arms and then drift away from the wave pattern. These early JWST results show that in situ star formation likely occurs in the spurs, and that the observed young stars are not simply the "leftovers" of stellar birth in the spiral arms. The excellent physical resolution and sensitivity that JWST can attain in nearby galaxies will well resolve individual star-forming regions and help us to better understand the earliest phases of star formation.

Keywords: galaxies; spiral galaxies; interstellar medium; star formation
ALMA-IMF. VIII. Combination of Interferometric Continuum Images with Single-dish Surveys and Structural Analysis of Six Protoclusters

We present the combination of ALMA-IMF and single-dish continuum images from the MUSTANG-2 Galactic Plane Survey (MGPS90) at 3 mm and the Bolocam Galactic Plane Survey (BGPS) at 1 mm. Six and 10 out of the 15 ALMA-IMF fields are combined with MGPS90 and BGPS, respectively. The combination is made via the feathering technique. We used the dendrogram algorithm throughout the combined images, and performed further analysis in the six fields with the combination in both bands (G012.80, W43-MM1, W43-MM2, W43-MM3, W51-E, W51-IRS2). In these fields, we calculated spectral index maps and used them to separate regions dominated by dust or free-free emission, and then performed further structural analysis. We report the basic physical parameters of the dust-dominated (column densities, masses) and ionized (emission measures, hydrogen ionization photon rates) structures. We also searched for multiscale relations in the dust-dominated structures across the analyzed fields, finding that the fraction of mass in dendrogram leaves (which we label leaf mass efficiency (LME)) as a function of molecular gas column density follows a similar trend: a rapid, exponential-like growth, with maximum values approaching 100% in most cases. The observed behavior of the LME with the gas column is tentatively interpreted as an indicator of large star formation activity within the ALMA-IMF protoclusters. W51-E and G012.80 stand out as cases with comparatively large and reduced potential for further star formation, respectively.

Keywords: stellar evolution; star clusters; single-dish antennas; interferometers
Population Synthesis of Neutron Star X-Ray Binaries Associated with Supernova Remnants

Neutron star X-ray binaries (NS XRBs) associated with supernova remnants (SNRs) are youngest X-ray binaries that can provide insights into the early evolution of X-ray binaries and formation properties of neutron stars. There are an increasing number of NS XRBs that have been discovered within SNRs in our own and nearby galaxies. In this work, we perform binary population synthesis calculations to simulate the population of NS XRBs associated with SNRs for different types of companions, including Roche-lobe-overfilling main-sequence stars, Be stars, and supergiants. We estimate their birth rates and present the distributions of orbital parameters and companion mass for each type of companion. Our calculations show that the majority of the companions are Be X-ray binaries (BeXRBs) and that a few BeXRBs are expected to be associated with SNRs in a Milky Way-type galaxy.

Keywords: x-ray binary stars; supernova remnants; neutron stars
Metallicity of Galactic RR Lyrae from Optical and Infrared Light Curves. I. Period-Fourier-Metallicity Relations for Fundamental-mode RR Lyrae

We present newly calibrated period-φ31-[Fe/H] relations for fundamental-mode RR Lyrae stars in the optical and, for the first time, mid-infrared. This work's calibration data set provides the largest and most comprehensive span of parameter space to date, with homogeneous metallicities from -3 ≲ [Fe/H] ≲ 0.4 and accurate Fourier parameters derived from 1980 ASAS-SN (V band) and 1083 WISE (NEOWISE extension, W1 and W2 bands) RR Lyrae stars with well-sampled light curves. We compare our optical period-φ31-[Fe/H] relation with those available in the literature and demonstrate that our relation minimizes systematic trends in the lower and higher metallicity range. Moreover, a direct comparison shows that our optical photometric metallicities are consistent with both those from high-resolution spectroscopy and globular clusters, supporting the good performance of our relation. We found an intrinsic scatter in the photometric metallicities (0.41 dex in the V band and 0.50 dex in the infrared) by utilizing large calibration data sets covering a broad metallicity range. This scatter becomes smaller when optical and infrared bands are used together (0.37 dex). Overall, the relations derived in this work have many potential applications, including large-area photometric surveys with James Webb Space Telescope in the infrared and LSST in the optical.

Keywords: rr lyrae variable stars; rrab variable stars; pulsating variable stars; globular star clusters; metallicity
Tidal Disruption on Stellar-mass Black Holes in Active Galactic Nuclei

Active galactic nuclei (AGNs) can funnel stars and stellar remnants from the vicinity of the galactic center into the inner plane of the AGN disk. Stars reaching this inner region can be tidally disrupted by the stellar-mass black holes in the disk. Such micro tidal disruption events (micro-TDEs) could be a useful probe of stellar interaction with the AGN disk. We find that micro-TDEs in AGNs occur at a rate of ~170 Gpc-3 yr-1. Their cleanest observational probe may be the electromagnetic detection of tidal disruption in AGNs by heavy supermassive black holes (M • ≳ 108 M ⊙) that cannot tidally disrupt solar-type stars. The reconstructed rate of such events from observations, nonetheless, appears to be much lower than our estimated micro-TDE rate. We discuss two such micro-TDE candidates observed to date (ASASSN-15lh and ZTF19aailpwl).

Keywords: tidal disruption; active galaxies
On the Impact of an Intermediate Duration X-Ray Burst on the Accretion Environment in IGR J17062-6143

We report on a spectroscopic analysis of the X-ray emission from IGR J17062-6143 in the aftermath of its 2020 June intermediate duration Type I X-ray burst. Using the Neutron Star Interior Composition Explorer, we started observing the source 3 hr after the burst was detected with the Monitor of All-sky X-ray Image Gas Slit Camera, and monitored the source for the subsequent 12 days. We observed the tail end of the X-ray burst-cooling phase, and find that the X-ray flux is severely depressed relative to its historic value for a three-day period directly following the burst. We interpret this intensity dip as the inner accretion disk gradually restoring itself after being perturbed by the burst irradiation. Superimposed on this trend we observed a 1.5 day interval during which the X-ray flux is sharply lower than the wider trend. This drop in flux could be isolated to the nonthermal components in the energy spectrum, suggesting that it may be caused by an evolving corona. Additionally, we detected a 3.4 keV absorption line at 6.3σ significance in a single 472 s observation while the burst emission was still bright. We tentatively identify the line as a gravitationally redshifted absorption line from burning ashes on the stellar surface, possibly associated with 40Ca or 44Ti.

Keywords: x-ray bursts; low-mass x-ray binary stars
Hubble Space Telescope Astrometry in the Orion Nebula Cluster: Census of Low-mass Runaways

We present a catalog of high-precision proper motions in the Orion Nebula Cluster (ONC), based on Treasury Program observations with the Hubble Space Telescope's (HST) ACS/WFC camera. Our catalog contains 2454 objects in the magnitude range of 14.2 < mF775W < 24.7, thus probing the stellar masses of the ONC from ∼0.4 M⊙ down to ∼0.02 M⊙ over an area of ∼550 arcmin2. We provide a number of internal velocity dispersion estimates for the ONC that indicate a weak dependence on stellar location and mass. There is good agreement with the published velocity dispersion estimates, although nearly all of them (including ours at ${\sigma }_{v,x}=0.94$ and ${\sigma }_{v,y}=1.25$ mas yr-1) might be biased by the overlapping young stellar populations of Orion A. We identified four new ONC candidate runaways based on HST and the Gaia DR 2 data, all with masses less than ∼1 M⊙. The total census of known candidate runaway sources is 10—one of the largest samples ever found in any Milky Way open star cluster. Surprisingly, none of them have tangential velocities exceeding 20 km s-1. If most of them indeed originated in the ONC, it may compel the re-examination of dynamical processes in very young star clusters. It appears that the mass function of the ONC is not significantly affected by the lost runaways.

Keywords: hubble space telescope; space astrometry; proper motions; young star clusters; low mass stars; stellar dynamics; runaway stars
Space Telescope and Optical Reverberation Mapping Project. XI. Disk-wind Characteristics and Contributions to the Very Broad Emission Lines of NGC 5548

In 2014 the NGC 5548 Space Telescope and Optical Reverberation Mapping campaign discovered a two-month anomaly when variations in the absorption and emission lines decorrelated from continuum variations. During this time the soft X-ray part of the intrinsic spectrum had been strongly absorbed by a line-of-sight (LOS) obscurer, which was interpreted as the upper part of a disk wind. Our first paper showed that changes in the LOS obscurer produces the decorrelation between the absorption lines and the continuum. A second study showed that the base of the wind shields the broad emission-line region (BLR), leading to the emission-line decorrelation. In that study, we proposed the wind is normally transparent with no effect on the spectrum. Changes in the wind properties alter its shielding and affect the spectral energy distribution (SED) striking the BLR, producing the observed decorrelations. In this work we investigate the impact of a translucent wind on the emission lines. We simulate the obscuration using XMM-Newton, NuSTAR, and Hubble Space Telescope observations to determine the physical characteristics of the wind. We find that a translucent wind can contribute a part of the He II and Fe Kα emission. It has a modest optical depth to electron scattering, which explains the fainter far-side emission in the observed velocity-delay maps. The wind produces the very broad base seen in the UV emission lines and may also be present in the Fe Kα line. Our results highlight the importance of accounting for the effects of such winds in the analysis of the physics of the central engine.

Keywords: seyfert galaxies; active galaxies; active galactic nuclei
The 300 pc Resolution Imaging of a z = 8.31 Galaxy: Turbulent Ionized Gas and Potential Stellar Feedback 600 Million Years after the Big Bang

We present the results of 300 pc resolution Atacama Large Millimeter/submillimeter Array imaging of the [O III] 88 μm line and dust continuum emission from a z = 8.312 Lyman-break galaxy MACS0416_Y1. The velocity-integrated [O III] emission has three peaks that are likely associated with three young stellar clumps of MACS0416_Y1, while the channel map shows a complicated velocity structure with little indication of a global velocity gradient unlike what was found in [C II] 158 μm at a larger scale, suggesting random bulk motion of ionized gas clouds inside the galaxy. In contrast, dust emission appears as two individual clumps apparently separating or bridging the [O III]/stellar clumps. The cross-correlation coefficient between dust and ultraviolet-related emission (i.e., [O III] and ultraviolet continuum) is unity on a galactic scale, while it drops at <1 kpc, suggesting well-mixed geometry of multiphase interstellar media on subkiloparsec scales. If the cutoff scale characterizes different stages of star formation, the cutoff scale can be explained by gravitational instability of turbulent gas. We also report on a kiloparsec-scale off-center cavity embedded in the dust continuum image. This could be a superbubble producing galactic-scale outflows, since the energy injection from the 4 Myr starburst suggested by a spectral energy distribution analysis is large enough to push the surrounding media creating a kiloparsec-scale cavity.

Keywords: galaxy formation; interstellar medium; superbubbles; stellar feedback; galaxy evolution
Speckle Interferometry at SOAR in 2020

The results of speckle interferometric observations at the 4.1 m Southern Astrophysical Research Telescope in 2020, as well as earlier unpublished data, are given, totaling 1735 measurements of 1288 resolved pairs and nonresolutions of 1177 targets. We resolved for the first time 59 new pairs or subsystems in known binaries, mostly among nearby dwarf stars. This work continues our long-term speckle program. Its main goal is to monitor orbital motion of close binaries, including members of high-order hierarchies and Hipparcos pairs in the solar neighborhood. We also report observations of 892 members of young moving groups and associations, where we resolved 103 new pairs.

Keywords: binary stars; multiple stars; stellar associations
Field Line Universal relaXer (FLUX): A Fluxon Approach to Coronal Magnetic Field Modeling

We describe a novel method for modeling the global, steady solar wind using photospheric magnetic fields as a driving boundary condition. Prior wind models in this class include both rapid heuristic methods that use potential field extrapolation and variants thereof, trading rigor for computation speed, and detailed 3D magnetohydrodynamic (MHD) models that attempt to simulate the entire solar corona with a degree of physical rigor, but require large amounts of computation. The Field Line Universal relaXer, an open-source numerical code that implements the "fluxon" semi-Lagrangian approach to MHD modeling, provides an intermediate approach between these two general classes. In particular, the fluxon approach to MHD describes the magnetic field through discrete analogs of magnetic field lines, relaxing these structures to a stationary state of force balance. In this work we introduce a 1D solar wind solution along each field line, providing an ensemble of solutions that are interpolated back onto a uniform grid at an outer boundary surface. This provides advantages in physical rigor over heuristic semianalytic techniques, and in computational efficiency over full 3D MHD techniques. Here we describe the underlying methodology and the FLUXPipe modeling pipeline process.

Keywords: the sun; solar physics; solar corona; solar wind
Constraints on the Hosts of UHECR Accelerators

Interactions of ultra-high-energy cosmic rays (UHECRs) in the surroundings of their accelerators can naturally explain the observed spectrum and composition of UHECRs, including the abundance of protons below the ankle. Here we show that astrophysical properties of the UHECR source environment such as the temperature, size, and magnetic field can be constrained by UHECR and neutrino data. Applying this to candidate sources with a simple structure shows that starburst galaxies are consistent with these constraints, but galaxy clusters are in tension with them. For multicomponent systems like active galactic nuclei and gamma-ray bursts, the results are indicative, but a customized analysis is needed for definitive conclusions.

Keywords: ultra-high-energy cosmic radiation; cosmic ray sources
On the Onset Delays of Solar Energetic Electrons and Protons: Evidence for a Common Accelerator

The processes responsible for the acceleration of solar energetic particles (SEPs) are still not well understood, including whether SEP electrons and protons are accelerated by common or separate processes. Using a numerical particle transport model that includes both pitch-angle and perpendicular spatial diffusion, we simulate, among other quantities, the onset delay for MeV electrons and protons and compare the results to observations of SEPs from widely separated spacecraft. Such observations have previously been interpreted, in a simple scenario assuming no perpendicular diffusion, as evidence for different electron and proton sources. We show that, by assuming a common particle source together with perpendicular diffusion, we are able to simultaneously reproduce the onset delays for both electrons and protons. We argue that this points toward a common accelerator for these particles. Moreover, a relatively broad particle source is required in the model to correctly describe the observations. This is suggestive of diffusive shock acceleration occurring at large shock structures playing a significant role in the acceleration of these SEPs.

Keywords: solar energetic particles
Physical Conditions and Particle Acceleration in the Kiloparsec Jet of Centaurus A

The nonthermal emission from the kiloparsec-scale jet of Centaurus A exhibits two notable features, bright diffuse emission and many compact knots, which have been intensively studied in X-ray and radio observations. H.E.S.S. recently reported that the very-high-energy gamma-ray emission from this object is extended along the jet direction beyond a kiloparsec from the core. Here, we combine these observations to constrain the physical conditions of the kiloparsec jet and study the origin of the nonthermal emission. We show that the diffuse jet is weakly magnetized ( ${\eta }_{{\rm{B}}}\sim {10}^{-2}$ ) and energetically dominated by thermal particles. We also show that knots are the sites of both amplified magnetic field and particle (re)acceleration. To keep sufficient energy in thermal particles, the magnetic and nonthermal particle energy in the knot regions is tightly constrained. The most plausible condition is an energy equipartition between them, ${\eta }_{{\rm{B}}}\sim {\eta }_{e}\sim 0.1$ . Such weak magnetic energy implies that particles in the knots are in the slow cooling regime. We suggest that the entire kiloparsec-scale diffuse emission could be powered by particles that are accelerated at and escaped from knots.

Keywords: active galactic nuclei; jets; cosmic rays; gamma-rays; high energy astrophysics
Observational Signatures of Electron-driven Chromospheric Evaporation in a White-light Flare

We investigate observational signatures of explosive chromospheric evaporation during a white-light flare (WLF) that occurred on 2022 August 27. Using the moment analysis, bisector techniques, and the Gaussian fitting method, redshifted velocities of less than 20 km s‑1 are detected in low-temperature spectral lines of Hα, C I, and Si IV at the conjugated flare kernels, which could be regarded as downflows caused by chromospheric condensation. Blueshifted velocities of ∼30‑40 km s‑1 are found in the high-temperature line of Fe XXI, which can be interpreted as upflows driven by chromospheric evaporation. A nonthermal hard X-ray (HXR) source is cospatial with one of the flare kernels, and the Doppler velocities are temporally correlated with the HXR fluxes. The nonthermal energy flux is estimated to be at least (1.3 ± 0.2) × 1010 erg s‑1 cm‑2. The radiation enhancement at Fe I 6569.2 Å and 6173 Å suggests that the flare is a WLF. Moreover, the while-light emission at Fe I 6569.2 Å is temporally and spatially correlated with the blueshift of the Fe XXI line, suggesting that both the white-light enhancement and the chromospheric evaporation are triggered and driven by nonthermal electrons. All of our observations support the scenario of an electron-driven explosive chromospheric evaporation in the WLF.

Keywords: solar flares; solar chromosphere; solar ultraviolet emission; solar x-ray emission; solar white-light flares
ALMA Fragmented Source Catalog in Orion (FraSCO). I. Outflow Interaction within an Embedded Cluster in OMC-2/FIR 3, FIR 4, and FIR 5

We present a high-angular resolution (~1″) and wide-field ( $2\buildrel{\,\prime}\over{.} 9\times 1\buildrel{\,\prime}\over{.} 9$ ) image of the 1.3 mm continuum, CO(J = 2-1) and SiO(J = 5-4) line emissions toward an embedded protocluster, FIR 3, FIR 4, and FIR 5, in the Orion Molecular Cloud 2 obtained from the Atacama Large Millimeter/submillimeter Array. We identify 51 continuum sources, 36 of which are newly identified in this study. Their dust masses, projected sizes, and H2 gas number densities are estimated to be 3.8 × 10-5-1.1 × 10-2 M ⊙, 290-2000 au, and 6.4 × 106-3.3 × 108 cm-3, respectively. The results of a Jeans analysis show that ~80% of the protostellar sources and ~15% of the prestellar sources are gravitationally bound. We identify 12 molecular outflows traced in the CO(J = 2-1) emission, six of which are newly detected. We spatially resolve shocked gas structures traced by the SiO(J = 5-4) emission in this region for the first time. We identify shocked gas originating from outflows and other shocked regions. These results provide direct evidence of an interaction between dust condensation, FIR 4, and an energetic outflow driven by HOPS-370 located within FIR 3. A comparison of the outflow dynamical timescales, fragmentation timescales, and protostellar ages shows that the previously proposed triggered star formation scenario in FIR 4 is not strongly supported. We also discuss the spatial distribution of filaments identified in our continuum image by comparing it with a previously identified hub-fiber system in the N2H+ line.

Keywords: protoclusters; protostars; giant molecular clouds; millimeter astronomy