adsabs/SciX_UAT_keywords huggingface dataset:
A Giant Loop of Ionized Gas Emerging from the Tumultuous Central Region of IC 5063

The biconical radiation pattern extending from an active galactic nucleus (AGN) may strongly photoionize the circumnuclear interstellar medium (ISM) and stimulate emission from the narrow-line region (NLR). Observations of the NLR may provide clues to the structure of dense material that preferentially obscures the bicone at certain angles, and may reveal the presence of processes in the ISM tied to AGN accretion and feedback. Ground-based integral field units may study these processes via well-understood forbidden diagnostic lines such as [O III] and [S II], but scales of ~tens of parsecs remain challenging to spatially resolve at these wavelengths for all but the nearest AGN. We present recent narrow-filter Hubble Space Telescope observations of diagnostic forbidden ([O III], [S II]) and Balmer (Hα, Hβ) lines in the NLR of IC 5063. This AGN's jet inclination into the plane of the galaxy provides an important laboratory for strong AGN-host interactions. We find evidence for a low-ionization loop which emits brightly in [S II] and [N II], and which may arise from plume-like hot outflows that ablate ISM from the galactic plane before escaping laterally. We also present spatially resolved Baldwin-Phillips-Terlevich diagnostic maps of the IC 5063 NLR. These maps suggest a sharp transition to lower-ionization states outside the jet path, and that such emission is dominated by ~10-40 pc clumps and filamentary structure at large (≫25°) angles from the bicone axis. Such emission may arise from precursorless shocks when AGN outflows impact low-density hot plasma in the cross cone. * Based on observations made with the NASA/ESA Hubble Space Telescope, obtained from the data archive at the Space Telescope Science Institute. STScI is operated by the Association of Universities for Research in Astronomy, Inc. under NASA contract NAS 5-26555. These observations are associated with programs #8598 and #15609.

Keywords: active galaxies; seyfert galaxies
Statistical Analysis of Lunar 1 Hz Waves Using ARTEMIS Observations

Like 1 Hz waves occurring in the upstream of various celestial bodies in the solar system, 1 Hz narrowband whistler-mode waves are often observed around the Moon. However, wave properties have not been thoroughly investigated, which makes it difficult to proclaim the generation mechanism of the waves. Using 5.5 yr wave data from ARTEMIS, we perform a detailed investigation of 1 Hz waves in the near-lunar space. The amplitude of lunar 1 Hz waves is generally 0.05-0.1 nT. In the geocentric solar ecliptic coordinates, the waves show no significant regional differentiation pattern but show an absence inside the magnetosphere. Correspondingly, in the selenocentric solar ecliptic coordinates, the waves can occur extensively at ~1.1-12 RL, while few events are observed in the lunar wake due to a lack of interaction with the solar wind. Furthermore, the wave distributions exhibit modest day-night and dawn-dusk asymmetries but less apparent north-south asymmetry. Compared with the nightside, more intense waves with lower peak wave frequency are present on the dayside. The preferential distribution of 1 Hz waves exhibits a moderate correlation with strong magnetic anomalies. The waves propagate primarily at wave normal angles <60° with an ellipticity of [-0.8, -0.3]. For stronger wave amplitudes and lower latitudes, 1 Hz waves generally have smaller wave normal angles and become more left-hand circularly polarized. Owing to the unique interaction between the Moon and solar wind, our statistical results might provide new insights into the generation mechanism(s) of 1 Hz waves in planetary plasma environments and promote the understanding of lunar plasma dynamics.

Keywords: solar wind; space plasmas; lunar science; shocks
X-Ray Afterglows from the Gamma-Ray Burst "Large-angle" Emission

We derive basic analytical results for the timing and decay of the gamma-ray burst (GRB) counterpart and delayed afterglow light curves for a brief emission episode from a relativistic surface endowed with angular structure, consisting of a uniform core of size ${\theta }_{c}$ (Lorentz factor ${{\rm{\Gamma }}}_{c}$ and surface emissivity ${I}_{\nu ^{\prime} }^{{\prime} }$ are angle independent) and an axially symmetric power-law envelope ( ${\rm{\Gamma }}\sim {\theta }^{-g}$ ). In this "large-angle emission" model, radiation produced during the prompt emission phase (GRB) at angles $\theta \gt {\theta }_{c}$ arrives at the observer well after the burst (delayed emission). The dynamical time range of the very fast decaying GRB "tail" and of the flat afterglow "plateau" and the morphology of the GRB counterpart/afterglow are all determined by two parameters: the core's parameter ${{\rm{\Gamma }}}_{c}{\theta }_{c}$ and the envelope's Lorentz factor index g, leading to three types of light curves that display three post-GRB phases (type 1: tail, plateau/slow decay, post-plateau/normal decay), two post-GRB phases (type 2: tail and fast decay), or just one (type 3: normal decay). We show how X-ray light-curve features can be used to determine core and envelope dynamical and spectral parameters. Testing of the large-angle emission model is done using the Swift/XRT X-ray emission of two afterglows of type 1 (GRB 060607A, GRB 061121), one of type 2 (GRB 061110A), and one of type 3 (GRB 061007). We find that the X-ray afterglows with plateaus require an envelope Lorentz factor ${\rm{\Gamma }}\sim {\theta }^{-2}$ and a comoving-frame emissivity ${I}_{\nu ^{\prime} }^{{\prime} }\sim {\theta }^{2}$ ; thus, for a typical afterglow spectrum ${F}_{\nu }\sim {\nu }^{-1}$ , the lab-frame energy release is uniform over the emitting surface.

Keywords: gamma-ray bursts; high energy astrophysics; non-thermal radiation sources
The Dynamic Coupling of Streamers and Pseudostreamers to the Heliosphere

The slow solar wind is generally believed to result from the interaction of open and closed coronal magnetic flux at streamers and pseudostreamers. We use three-dimensional magnetohydrodynamic simulations to determine the detailed structure and dynamics of open-closed interactions that are driven by photospheric convective flows. The photospheric magnetic field model includes a global dipole giving rise to a streamer together with a large parasitic polarity region giving rise to a pseudostreamer that separates a satellite coronal hole from the main polar hole. Our numerical domain extends out to 30R ⊙ and includes an isothermal solar wind, so that the coupling between the corona and heliosphere can be calculated rigorously. This system is driven by imposing a large set of quasi-random surface flows that capture the driving of coronal flux in the vicinity of streamer and pseudostreamer boundaries by the supergranular motions. We describe the resulting structures and dynamics. Interchange reconnection dominates the evolution at both streamer and pseudostreamer boundaries, but the details of the resulting structures are clearly different from one another. Additionally, we calculate in situ signatures of the reconnection and determine the dynamic mapping from the inner heliosphere back to the Sun for a test spacecraft orbit. We discuss the implications of our results for interpreting observations from inner heliospheric missions, such as Parker Solar Probe and Solar Orbiter, and for space weather modeling of the slow solar wind.

Keywords: solar physics; solar magnetic reconnection; solar corona; solar coronal holes; magnetohydrodynamics; slow solar wind
Molecules with ALMA at Planet-forming Scales (MAPS). XI. CN and HCN as Tracers of Photochemistry in Disks

UV photochemistry in the surface layers of protoplanetary disks dramatically alters their composition relative to previous stages of star formation. The abundance ratio CN/HCN has long been proposed to trace the UV field in various astrophysical objects; however, to date the relationship between CN, HCN, and the UV field in disks remains ambiguous. As part of the ALMA Large Program MAPS (Molecules with ALMA at Planet-forming Scales), we present observations of CN N = 1-0 transitions at 0.″3 resolution toward five disk systems. All disks show bright CN emission within ~50-150 au, along with a diffuse emission shelf extending up to 600 au. In all sources we find that the CN/HCN column density ratio increases with disk radius from about unity to 100, likely tracing increased UV penetration that enhances selective HCN photodissociation in the outer disk. Additionally, multiple millimeter dust gaps and rings coincide with peaks and troughs, respectively, in the CN/HCN ratio, implying that some millimeter substructures are accompanied by changes to the UV penetration in more elevated disk layers. That the CN/HCN ratio is generally high (>1) points to a robust photochemistry shaping disk chemical compositions and also means that CN is the dominant carrier of the prebiotically interesting nitrile group at most disk radii. We also find that the local column densities of CN and HCN are positively correlated despite emitting from vertically stratified disk regions, indicating that different disk layers are chemically linked. This paper is part of the MAPS special issue of the Astrophysical Journal Supplement.

Keywords: astrochemistry; protoplanetary disks; interstellar molecules
Precise Empirical Determination of Metallicity Dependence of Near-infrared Period-Luminosity Relations for RR Lyrae Variables

RR Lyrae variables are excellent Population II distance indicators thanks to their well-defined period-luminosity relations (PLRs) at infrared wavelengths. We present results of near-infrared (NIR) monitoring of Galactic globular clusters to empirically quantify the metallicity dependence of NIR PLRs for RR Lyrae variables. Our sample includes homogeneous, accurate, and precise photometric data for 964 RR Lyrae variables in 11 globular clusters covering a large metallicity range (Δ[Fe/H] ~ 2 dex). We derive JHK s -band period-luminosity-metallicity (PLZ) and period-Wesenheit-metallicity (PWZ) relations anchored using 346 Milky Way field RR Lyrae stars with Gaia parallaxes, and simultaneously solved for independent distances to globular clusters. We find a significant metallicity dependence of ~0.2 mag dex-1 in the JHK s -band PLZ and PWZ relations for RR Lyrae stars independent of the adopted metallicity scale. The metallicity coefficients and the zero-points of the empirical PLZ and PWZ relations are in excellent agreement with the predictions from the horizontal branch evolution and pulsation models. Furthermore, RR Lyrae-based distances to our sample of globular clusters are also statistically consistent with other independent measurements in the literature. Our recommended empirical JHK s -band PLZ relations for RR Lyrae stars with periods of fundamental mode pulsation (P f) are: \begin{eqnarray*}\begin{array}{rcl}{M}_{J} & = & -0.44\,(\pm 0.03)-1.83\,(\pm 0.02)\mathrm{log}({P}_{{\rm{f}}})+0.20\,(\pm 0.02)\,[\mathrm{Fe}/{\rm{H}}]\,(\sigma =0.05\,\mathrm{mag})\\ {M}_{H} & = & -0.74\,(\pm 0.02)-2.29\,(\pm 0.02)\mathrm{log}({P}_{{\rm{f}}})+0.19\,(\pm 0.01)[\mathrm{Fe}/{\rm{H}}]\,(\sigma =0.05\,\mathrm{mag})\\ {M}_{{K}_{s}} & = & -0.80\,(\pm 0.02)-2.37\,(\pm 0.02)\mathrm{log}({P}_{{\rm{f}}})+0.18\,(\pm 0.01)\,[\mathrm{Fe}/{\rm{H}}]\,(\sigma =0.05\,\mathrm{mag}).\end{array}\end{eqnarray*}

Keywords: globular star clusters; rr lyrae variable stars; distance indicators
The Velocity Dispersion Function for Quiescent Galaxies in Nine Strong-lensing Clusters

We measure the central stellar velocity dispersion function for quiescent galaxies in a set of nine northern clusters in the redshift range 0.18 < z < 0.29 and with strong lensing arcs in Hubble Space Telescope images. The velocity dispersion function links galaxies directly to their dark matter halos. From dense SDSS and MMT/Hectospec spectroscopy, we identify 222-463 spectroscopic members in each cluster. We derive physical properties of cluster members including redshift, ${D}_{n}4000$ , and central stellar velocity dispersion and we include a table of these measurements for 3419 cluster members. We construct the velocity dispersion functions for quiescent galaxies with ${D}_{n}4000$ > 1.5 and within R200. The cluster velocity dispersion functions all show excesses at σ ≳ 250 km s-1 compared to the field velocity dispersion function. The velocity dispersion function slope at large velocity dispersion (σ > 160 km s-1) is steeper for more massive clusters, consistent with the trend observed for cluster luminosity functions. The spatial distribution of galaxies with large velocity dispersion at radii larger than R200 further underscores the probable major role of dry mergers in the growth of massive cluster galaxies during cluster assembly.

Keywords: early-type galaxies; galaxy clusters; luminosity function; galaxy mass distribution; redshift surveys
Measurements of the Magnetic Field Strengths at the Bases of Stellar Coronae Using the Magnetic-field-induced Transition Theory

Measurements of the magnetic field in the stellar coronae are extremely difficult. Recently, it was proposed that the magnetic-field-induced transition (MIT) of the Fe X 257 Å line can be used to measure the coronal magnetic field of the Sun. We performed forward modeling with a series of global stellar magnetohydrodynamics models to investigate the possibility of extending this method to other late-type stars. We first synthesized the emissions of several Fe X lines for each stellar model, then calculated the magnetic field strengths using the intensity ratios of Fe X 257 Å to several other Fe X lines based on the MIT theory. Finally, we compared the derived field strengths with those in the models, and concluded that this method can be used to measure at least the magnetic field strengths at the coronal bases of stars with a mean surface magnetic flux density about one order of magnitude higher than that of the Sun. Our investigation suggests the need for an extreme ultraviolet spectrometer to perform routine measurements of the stellar coronal magnetic field.

Keywords: magnetohydrodynamics; stellar coronae; stellar magnetic fields
Betatron Acceleration of Suprathermal Electrons within a Small-scale Flux Rope in the Solar Wind

A growing body of evidence from observations, theories, and simulations indicates that particles can be effectively accelerated in solar wind regions filled with dynamic small-scale flux ropes (FRs). The main acceleration mechanisms identified in simulations include parallel electric field acceleration, first-order Fermi acceleration, and generalized betatron acceleration in contracting or merging small-scale FRs. However, direct identification of these acceleration mechanisms from in situ measurements remains a challenge. Here we present a distinct event of local betatron acceleration within a contracting small-scale FR in the solar wind, due to a local compression. In this event, the lower-energy halo electrons were effectively accelerated through the betatron mechanism, whereas the higher-energy suprathermal electrons predominated by the superhalo component were almost not energized. The halo electron energization processes via the betatron mechanism are reproduced using an analytical model. Further examination of small-scale FRs in the vicinity of the heliospheric current sheet over the period 1995-2020 indicates that in situ signatures of the betatron acceleration process are essentially elusive.

Keywords: interplanetary particle acceleration; interplanetary physics; solar wind
IRIS Mg II Observations and Non-LTE Modeling of Off-limb Spicules in a Solar Polar Coronal Hole

We investigated the off-limb spicules observed in the Mg II h and k lines by IRIS in a solar polar coronal hole. We analyzed the large data set of obtained spectra to extract quantitative information about the line intensities, shifts, and widths. The observed Mg II line profiles are broad and double peaked at lower altitudes, broad but flat topped at middle altitudes, and narrow and single peaked with the largest Doppler shifts at higher altitudes. We use one-dimensional non-LTE vertical slab models (I.e., models that consider departures from local thermodynamic equilibrium) in single-slab and multi-slab configurations to interpret the observations and to investigate how a superposition of spicules along the line of sight (LOS) affects the synthetic Mg II line profiles. The used multi-slab models either are static, I.e., without any LOS velocities, or assume randomly assigned LOS velocities of individual slabs, representing the spicule dynamics. We conducted such single-slab and multi-slab modeling for a broad set of model input parameters and showed the dependence of the Mg II line profiles on these parameters. We demonstrated that the observed line widths of the h and k line profiles are strongly affected by the presence of multiple spicules along the LOS. We later showed that the profiles obtained at higher altitudes can be reproduced by single-slab models representing individual spicules. We found that the multi-slab model with a random distribution of the LOS velocities ranging from -25 to 25 km s-1 can well reproduce the width and the shape of Mg II profiles observed at middle altitudes.

Keywords: solar chromosphere; solar spicules; solar ultraviolet emission; spectroscopy; astronomy data analysis; radiative transfer simulations
XMM-Newton and Chandra Observations of the Candidate Fermi-LAT Pulsar 4FGL J1015.5-6030

4FGL J1015.5-6030 is an unidentified Fermi-LAT source hosting a bright, extended X-ray source whose X-ray spectrum is consistent with that of a young pulsar, yet no pulsations have been found. Here we report on XMM-Newton timing and Chandra imaging observations of the X-ray counterpart of 4FGL J1015.5-6030. We find no significant periodicity from the source and place a 3σ upper limit on its pulsed fraction of 34%. The Chandra observations resolve the point source from the extended emission. We find that the point source's spectrum is well fit by a blackbody model, with temperature kT = 0.205 ± 0.009 keV, plus a weak power-law component, which is consistent with a thermally emitting neutron star with a magnetospheric component. The extended emission spans angular scales of a few arcseconds up to about 30″ from the point source and its spectrum is well fit by a power-law model with a photon index Γ = 1.70 ± 0.05. The extended emission's spectrum and 0.5-10 keV luminosity of 4 × 1032 erg s-1 (at a plausible distance of 2 kpc) are consistent with that of a pulsar wind nebula. Based on a comparison to other GeV and X-ray pulsars, we find that this putative pulsar is likely a middle-aged (i.e., τ ~ 0.1-1 Myr) radio-quiet pulsar with $\dot{E}\sim {10}^{34}\mbox{--}{10}^{35}$ erg s-1.

Keywords: pulsars; pulsar wind nebulae; gamma-ray sources; x-ray sources
Termination Shock as a Source of Unusual Solar Radio Bursts

Using centimeter-wave and decimeter-wave solar radio spectral observations of the flares of 2003 November 18 and 2004 September 12, we have discussed two type-II-like bursts at the meter waves. The radio bursts show that the ordinary frequency drift from high to low frequencies slows down and stops, and a frequency drift from low to high frequencies appears. An analysis of all data on the corresponding flares provides evidence of the formation of quasi-standing fast-mode shocks (termination shocks, TSs). TSs are able to generate energetic electrons, responsible for the appearance of new sources of hard X-ray radiation and generation of fast radio bursts (spikes), fibers, and zebra structures. The sources of the radio emission bands with the unusual frequency drift are situated above the top of the post-flare loops (lower TS) or are connected with the erupting prominence or coronal mass ejection (upper TS). Estimations of the critical Mach numbers for the ordinary plasma parameters in the solar flares give the values Mcr = 1.1-1.3 easily realized in the flare events. The conditions necessary for the generation of unusual radio bursts are likely to occur in the helmet-shaped magnetic structures in the solar corona.

Keywords: the sun
Growth of Massive Disks and Early Disk Fragmentation in Primordial Star Formation

Recent high-resolution simulations demonstrate that disks around primordial protostars easily fragment in the accretion phase before protostars accrete less than a solar mass. To understand why gravitational instability generally causes fragmentation so early, we develop a one-dimensional (1D) nonsteady model of the circumstellar disk that takes the mass supply from an accretion envelope into account. We also compare the model results to a three-dimensional (3D) numerical simulation performed with a code employing adaptive mesh refinement. Our model shows that the self-gravitating disk, through which the Toomre Q parameter is nearly constant at Q ∼ 1, gradually spreads as the disk is fed by the gas infalling from the envelope. We further find that the accretion rate onto the star is an order of magnitude smaller than the mass supply rate onto the disk. This discrepancy makes the disk more massive than the protostar in an early evolutionary stage. Most of the infalling gas is used to extend the outer part of the self-gravitating disk rather than transferred inward toward the star through the disk. We find that similar evolution also occurs in 3D simulations, where the disk becomes three times more massive than the star before the first fragmentation occurs. Our 1D disk model well explains the evolution of the disk-to-star mass ratio observed in the simulation. We argue that the formation of such a massive disk leads to early disk fragmentation.

Keywords: population iii stars; circumstellar disks
Dense and Warm Neutral Gas in BR 1202-0725 at z = 4.7 as Traced by the [O I] 145 μm Line

We report the detection of [O I] 145.5 μm in the BR 1202-0725 system, a compact group at z = 4.7 consisting of a quasar (QSO), a submillimeter-bright galaxy (SMG), and three faint Lyα emitters. By taking into account the previous detections and upper limits, the [O I] /[C II] line ratios of the now five known high-z galaxies are higher than or on the high end of the observed values in local galaxies ([O I] /[C II] ≳ 0.13). The high [O I] /[C II] ratios and the joint analysis with previous detection of [N II] lines for both of the QSO and the SMG suggest the presence of warm and dense neutral gas in these highly star-forming galaxies. This is further supported by new CO (12-11) line detections and a comparison with cosmological simulations. There is a possible positive correlation between the [N II] 122/205 line ratio and the [O I] /[C II] ratio when all local and high-z sources are taken into account, indicating that the denser the ionized gas, the denser and warmer the neutral gas (or vice versa). The detection of the [O I] line in the BR 1202-0725 system with a relatively short amount of integration with Atacama Large Millimeter/submillimeter Array (ALMA) demonstrates the great potential of this line as a dense gas tracer for high-z galaxies.

Keywords: galaxy evolution; quasars; submillimeter astronomy; starburst galaxies; interstellar line emission