Sazuna/UAT_keywords huggingface dataset:
Lyman Continuum Emission Escaping from Luminous Green Pea Galaxies at z = 0.5. Compact starburst galaxies are thought to include many or most of the galaxies from which substantial Lyman continuum emission can escape into the intergalactic medium. Li &amp; Malkan used Sloan Digital Sky Survey photometry to find a population of such starburst galaxies at z ∼ 0.5. They were discovered by their extremely strong [O III] λλ4959+5007 emission lines, which produce a clearly detectable excess brightness in the i bandpass, compared with surrounding filters. We therefore used the Hubble Space Telescope (HST)/COS spectrograph to observe two of the newly discovered i-band excess galaxies around their Lyman limits. One has strongly detected continuum below its Lyman limit, corresponding to a relative escape fraction of ionizing photons of 20% ± 2%. The other, which is less compact in UV imaging, has a 2&amp;sgr; upper limit to its Lyman escape fraction of &lt;5%. Before the UV spectroscopy, the existing data could not distinguish these two galaxies. Although a sample of two is hardly sufficient for statistical analysis, it shows the possibility that some fraction of these strong [O III] emitters as a class have ionizing photons escaping. The differences might be determined by the luck of our particular viewing geometry. Obtaining the HST spectroscopy revealed that the Lyman-continuum-emitting galaxy differs in having no central absorption in its prominent Lyα emission-line profile. The other target, with no escaping Lyman continuum, shows the more common double-peaked Lyα emission.

Keywords: Starburst galaxies, O stars, Near ultraviolet astronomy, Compact dwarf galaxies, Emission line galaxies, Ultraviolet astronomy, Primordial galaxies, Star formation, Galaxy evolution, Lyman-alpha galaxies, Reionization, H II regions
The Carina Nebula and Gum 31 Molecular Complex. III. The Distribution of the 1-3 GHz Radio Continuum across the Whole Nebula. We report the most detailed 1-3 GHz radio continuum emission map of the nearest region of massive-star formation, the Carina Nebula. As part of a large program with the Australia Telescope Compact Array, we have covered ∼12 deg2, achieving an angular resolution of ∼16″, representing the largest and most complete map of the radio continuum to date. Our continuum map shows a spectacular and complex distribution of emission across the nebula, with multiple structures such as filaments, shells, and fronts across a wide range of size scales. The ionization fronts have advanced far into the southern and northern region of the Galactic plane, as fronts are clearly detected at distances of ∼80 pc from the stellar clusters in the center. We estimated an ionization photon luminosity QH = (7. 8 ± 0.8) × 1050 s-1, which corresponds to ∼85% of the total value obtained from stellar population studies. Thus, approximately 15% of the ionizing flux has escaped from the nebula into the diffuse Galactic interstellar medium. Comparison between radio continuum and the hydrogen atomic and molecular gas maps offers a clear view of the bipolar outflow driven by the energy released by the massive stellar clusters that also affects the fraction of molecular gas across the nebula. Comparison between 8 μm and 70 μm emission maps and the radio continuum reveals how the hot gas permeates through the molecular cloud; shapes the material into features such as pillars, small shells, and arc-like structures; and ultimately escapes.

Keywords: Radio astronomy, Photoionization, Interstellar radiation field, Star forming regions, Massive stars, Ionization, Radio continuum emission, H II regions
The Dielectric Function of "Astrodust" and Predictions for Polarization in the 3.4 and 10 μm Features. The dielectric function of interstellar dust material is modeled using observations of extinction and polarization in the infrared, together with estimates for the mass of interstellar dust. The "astrodust" material is assumed to be a mix of amorphous silicates and other materials, including hydrocarbons producing an absorption feature at 3.4 μm. The detailed shape of the 10 μm polarization profile depends on the assumed porosity and grain shape, but the 10 μm spectropolarimetric data are not yet good enough to clearly favor one shape over another, nor to constrain the porosity. The expected 3.4 μm feature polarization is consistent with existing upper limits, provided the 3.4 μm absorption is preferentially located in grain surface layers; a separate population of non-aligned carbonaceous grains is not required. We predict the 3.4 μm polarization feature to be (Δp)3.4 μm/p(10 μm) ≈ 0.016, just below current upper limits. Polarization by the same grains at submillimeter wavelengths is also calculated.

Keywords: Interstellar dust, Silicate grains, Polycyclic aromatic hydrocarbons, Very small grains, Solid matter physics, Interstellar dust extinction, Carbonaceous grains, Interstellar dust processes
Switchbacks Explained: Super-Parker Fields—The Other Side of the Sub-Parker Spiral. We provide a simple geometric explanation for the source of switchbacks and associated large and one-sided transverse flows in the solar wind observed by the Parker Solar Probe (PSP). The more radial, sub-Parker spiral structure of the heliospheric magnetic field observed previously by Ulysses, ACE, and STEREO is created within rarefaction regions where footpoint motion from the source of fast into slow wind at the Sun creates a magnetic fieldline connection across solar wind speed shear. Conversely, when footpoints move from the source of slow wind into faster wind, a super-Parker spiral field structure is formed: below the Alfvén critical point, one-sided transverse field-aligned flows develop; above the Alfvén critical point, the field structure contracts between adjacent solar wind flows, and the radial field component decreases in magnitude with distance from the Sun, eventually reversing into a switchback. The sub-Parker and super-Parker spirals behave functionally as opposites. Observations from PSP confirm the paucity of switchbacks within rarefaction regions and immediately outside these rarefaction regions, we observe numerous switchbacks in the magnetic field that are directly associated with abrupt transients in solar wind speed. The magnetic field strength, the radial component of the magnetic field, the speed gradients, radial Alfvén speed, and the ratio of the sound speed to the radial Alfvén speed all conform to predictions based on the sub-Parker and super-Parker spirals within rarefaction regions and solar wind speed enhancements (spikes or jets), respectively. Critically, the predictions associated with the super-Parker spiral naturally explain the observations of switchbacks being associated with unexpectedly large and one-sided tangential flows.

Keywords: Solar coronal loops, Solar wind, Solar spicules, Solar coronal waves, Solar coronal holes, Solar magnetic fields, Interplanetary magnetic fields, Active solar corona, Solar coronal plumes, Astronomical location
Formation of "Blanets" from Dust Grains around the Supermassive Black Holes in Galaxies. In Wada et al. (2019), we proposed for the first time that a new class of planets, blanets, can be formed around supermassive black holes in the galactic center. Here, we investigate the dust coagulation processes and physical conditions of the blanet formation outside the snowline (rsnow ∼ several parsecs) in more detail, especially considering the effect of the radial drift of the dust aggregates. We found that a dimensionless parameter $\alpha ={v}_{t}^{2}/{c}_{s}^{2}$ , where vt is the turbulent velocity and cs is the sound velocity, describing the turbulent viscosity should be smaller than 0.04 in the circumnuclear disk to prevent the destruction of the aggregates due to collision. The formation timescale of blanets τGI at rsnow is, τGI ≃ 70-80 Myr for α = 0.01 - 0.04 and MBH = 106M⊙. The mass of the blanets ranges from ∼20ME to 3000ME in r &lt; 4 pc for α = 0.02 (ME is the Earth mass), which is in contrast with 4ME-6ME for the case without the radial drift. Our results suggest that blanets could be formed around relatively low-luminosity active galactic nuclei (Lbol ∼ 1042 erg s-1) during their lifetime (≲108 yr).

Keywords: Interstellar dust, Supermassive black holes, Exoplanet astronomy, Galaxy circumnuclear disk, Exoplanet formation
Deciphering the 3D Orion Nebula-IV: The HH 269 Flow Emerges from the Orion-S Embedded Molecular Cloud. We have extended the membership and determined the 3D structure of the large (0.19 pc) HH 269 sequence of shocks in the Orion Nebula. All of the components lie along a track that is highly tilted to the plane of the sky and emerge from within the Orion-S embedded molecular cloud. Their source is probably either the highly obscured mm 9 source associated with a high N2H+ density core (more likely) or the more distant star COUP 632 (less likely). The former must be located in the photon dominated region (PDR) underlying the ionized surface of the Orion-S Cloud, while the latter would be embedded within the Orion-S Cloud. The flows seem to be episodic, with intervals of 1900-2600 yr or 700-2600 yr if COUP 632 is the source.

Keywords: Herbig-Haro objects, H II regions
The Evolution of NGC 7465 as Revealed by Its Molecular Gas Properties. We present ALMA observations of CO isotopologues and high-density molecular tracers (HCN, HCO+, CN, etc.) in NGC 7465, an unusually gas-rich early-type galaxy that acquired its cold gas recently. In the inner 300 pc, the molecular gas kinematics are misaligned with respect to all other galaxy components; as the gas works its way inward, it is torqued into polar orbits about the stellar kinematically decoupled core (KDC), indicating that the stellar KDC is not related to the current gas accretion event. The galaxy also exhibits unusually high 12CO/13CO line ratios in its nucleus but typical 13CO/C18O ratios. Our calculations show that this result does not necessarily indicate an unusual [12CO/13CO] abundance ratio but rather that 12CO (1-0) is optically thin due to high temperatures and/or large line widths associated with the inner decoupled, misaligned molecular structure. Line ratios of the higher-density tracers suggest that the densest phase of molecular gas in NGC 7465 has a lower density than is typical for nearby galaxies, possibly as a result of the recent gas accretion. All of the observed molecular properties of NGC 7465 are consistent with it having acquired its molecular (and atomic) gas from a spiral galaxy. Further detailed studies of the CO isotopologues in other early-type galaxies would be valuable for investigating the histories of those that may have acquired their gas from dwarfs. Finally, these ALMA data also show an unidentified line source that is probably a background galaxy similar to those found at z = 1-3 in blind CO surveys.

Keywords: Interstellar molecules, Molecular gas, Early-type galaxies, CO line emission
The Neupert Effect of Flare Ultraviolet and Soft X-Ray Emissions. We model the Neupert effect that relates flare heating energy with the observed soft X-ray (SXR) emission. The traditional form of the Neupert effect refers to the correlation between the time-integrated hard X-ray or microwave light curve and the SXR light curve. In this paper, we instead use as the proxy for heating energy the ultraviolet (UV) emission at the footpoints of flare loops and modify the model of the Neupert effect by taking into account the discrete nature of flare heating, as well as cooling. In the modified empirical model, spatially resolved UV light curves from the transition region or upper chromosphere are each convolved with a kernel function characterizing the decay of the flare loop emission. Contributions by all loops are summed to compare with the observed total SXR emission. The model has successfully reproduced the observed SXR emission from its rise to decay. To estimate the heating energies in flare loops, we also employ the UV footpoint calorimeter (UFC) method that infers heating rates in flare loops from these UV light curves and models the evolution of flare loops with a zero-dimensional hydrodynamic code. The experiments show that a multitude of impulsive heating events do not well reproduce the observed flare SXR light curve, but a two-phase heating model leads to better agreement with observations. Comparison of the two models of the Neupert effect further allows us to calibrate the UFC method and improve the estimate of heating rates in flare loops continuously formed by magnetic reconnection throughout the flare evolution.

Keywords: Solar flares, Solar ultraviolet emission, Solar magnetic reconnection, Solar x-ray emission
The Fast-evolving Type Ib Supernova SN 2015dj in NGC 7371. We present the detailed optical evolution of a Type Ib SN 2015dj in NGC 7371, using data spanning up to ∼170 days after discovery. SN 2015dj shares similarity in light-curve shape with SN 2007gr and peaks at MV = -17.37 ± 0.02 mag. Analytical modeling of the quasi bolometric light curve yields 0.06 ± 0.01 M⊙ of 56Ni, ejecta mass ${M}_{\mathrm{ej}}={1.4}_{-0.5}^{+1.3}$ M⊙, and kinetic energy ${E}_{{\rm{k}}}={0.7}_{-0.3}^{+0.6}\times {10}^{51}$ erg. The spectral features show a fast evolution and resemble those of spherically symmetric ejecta. The analysis of nebular phase spectral lines indicates a progenitor mass between 13-20 M⊙, suggesting a binary scenario.

Keywords: Type Ib supernovae, Core-collapse supernovae
3D Magnetothermal Simulations of Tangled Crustal Magnetic Field in Central Compact Objects. Central compact objects (CCOs) are young neutron stars emitting thermal X-rays with bolometric luminosities LX in the range of 1032-1034 erg s-1. Gourgouliatos, Hollerbach, and Igoshev recently suggested that peculiar emission properties of CCOs can be explained by tangled magnetic field configurations formed in a stochastic dynamo during the proto-neutron star stage. In this case the magnetic field consists of multiple small-scale components with negligible contribution of global dipolar field. We study numerically three-dimensional magnetothermal evolution of tangled crustal magnetic fields in neutron stars. We find that all configurations produce complicated surface thermal patterns that consist of multiple small hot regions located at significant separations from each other. The configurations with initial magnetic energy of (2.5-10) × 1047 erg have temperatures of hot regions that reach ≈ 0.2 keV, to be compared with the bulk temperature of ≈ 0.1 keV in our simulations with no cooling. A factor of two in temperature is also seen in observations of CCOs. The hot spots produce periodic modulations in light curve with typical amplitudes of ≤9%-11%. Therefore, the tangled magnetic field configuration can explain thermal emission properties of some CCOs.

Keywords: Neutron stars, Magnetohydrodynamics, Astrophysical magnetism, Magnetic fields, Astrophysical fluid dynamics, Magnetohydrodynamical simulations
A Luminous X-Ray Transient in SDSS J143359.16+400636.0: A Likely Tidal Disruption Event. We present the discovery of a luminous X-ray transient, serendipitously detected by Swift's X-ray Telescope on 2020 February 5, located in the nucleus of the galaxy SDSS J143359.16+400636.0 at z = 0.099 (luminosity distance DL = 456 Mpc). The transient was observed to reach a peak luminosity of ∼1044 erg s-1 in the 0.3-10 keV X-ray band, which was ∼20 times more than the peak optical/UV luminosity. Optical, UV, and X-ray light curves from the Zwicky Transient Facility and Swift show a decline in flux from the source consistent with t-5/3, and observations with NuSTAR and Chandra show a soft X-ray spectrum with photon index Γ = 2.9 ± 0.1. The X-ray/UV properties are inconsistent with well-known active galactic nucleus properties and have more in common with known X-ray tidal disruption events (TDEs), leading us to conclude that it was likely a TDE. The broadband spectral energy distribution can be described well by a disk blackbody model with an inner disk temperature of ${7.3}_{-0.8}^{+0.3}\times {10}^{5}$ K, with a large fraction (&gt;40%) of the disk emission upscattered into the X-ray band. An optical spectrum taken with Keck/LRIS after the X-ray detection reveals LINER line ratios in the host galaxy, suggesting low-level accretion onto the supermassive black hole prior to the event, but no broad lines or other indications of a TDE were seen. The stellar velocity dispersion implies that the mass of the supermassive black hole powering the event is log(MBH/M☉) = 7.41 ± 0.41, and we estimate that at peak the Eddington fraction of this event was ∼50%. This likely TDE was not identified by wide-field optical surveys or optical spectroscopy, indicating that more events like this would be missed without wide-field UV or X-ray surveys.

Keywords: Supermassive black holes, Tidal disruption, Transient sources, X-ray transient sources, X-ray sources
X-Ray Intraday Variability of the TeV Blazar PKS 2155-304 with Suzaku during 2005-2014. We have examined 13 pointed observations of the TeV-emitting high synchrotron peak blazar PKS 2155-304, taken by the Suzaku satellite throughout its operational period. We found that the blazar showed large-amplitude intraday variabilities in the soft (0.8-1.5 keV) and the hard (1.5-8.0 keV) bands in the light curves. Spectral variability on intraday timescales is estimated using the hardness ratio. The blazar usually becomes harder when brighter and vice versa, following the typical behavior of high synchrotron peak blazars. The power spectral density analyses of 11 out of 13 light curves in the total energy (0.8-8.0 keV) are found to be dominated by red noise, with power-law spectral indices that span a large range, from -2.81 to -0.88. Discrete correlation function analyses of all the 13 light curves between the soft and the hard bands show that they are well correlated and peak at, or very close to, zero lag. This indicates that the emissions in soft and hard bands are probably cospatial and emitted from the same population of leptons. Considering fluxes versus variability timescales, we found no correlation on intraday timescales, implying that X-ray emission from PKS 2155-304 is not dominated by simple changes in the Doppler factor. We briefly discuss the most likely emission mechanisms responsible for the observed flux and spectral variabilities and place constraints on magnetic field strength and Lorentz factors of the electrons emitting the X-rays in the most likely scenario.

Keywords: Timing variation methods, Blazars, X-ray astronomy
Modeling the in-orbit Background of PolarLight. PolarLight is a gas pixel X-ray polarimeter mounted on a CubeSat, which was launched into a Sun-synchronous orbit in 2018 October. We build a mass model of the whole CubeSat with the Geant4 toolkit to simulate the background induced by the cosmic X-ray background (CXB) and high-energy charged particles in the orbit. The simulated energy spectra and morphologies of event images both suggest that the background measured with PolarLight is dominated by high-energy electrons, with a minor contribution from protons and the CXB. The simulation reveals that, in the energy range 2-8 keV, roughly 28% of background events are caused by energy deposited by a secondary electron with an energy of a few keV, in a physical process identical to the detection of X-rays. Thus, this fraction of the background cannot be discriminated from X-ray events. The background distribution is uneven on the detector plane, with an enhancement near the edges. The edge effect occurs because high-energy electrons tend to produce long tracks, which are discarded by the readout electronics unless energy is partially deposited near the edges. The internal background rate is expected to be around 6 × 10-3 counts s-1 cm-2 at 2-8 keV if an effective particle discrimination algorithm can be applied. This indicates that the internal background should be negligible for future focusing X-ray polarimeters with a focal size of the order of millimeters.

Keywords: X-ray astronomy, Space telescopes, X-ray detectors, Polarimetry
Transient Formation of Loops in the Core of an Active Region. We study the formation of transient loops in the core of the AR 11890. For this purpose, we have used the observations recorded by the Atmospheric Imaging Assembly (AIA) and the Interface Region Imaging Spectrograph (IRIS). For photospheric field configuration, we have used the line-of-sight (LOS) magnetograms obtained from the Helioseismic and Magnetic Imager. The transient is simultaneously observed in all the UV and EUV channels of AIA and the three slit-jaw images from IRIS. The coexistence of the transient in all AIA and IRIS SJI channels suggests the transient's multithermal nature. The transient consists of short loops located at the base of the transient, as well as long loops. A differential emission measure analysis shows that the transient has a clumpy structure. The highest emission observed at the base is within the temperature bin of $\mathrm{log}T=6.65\mbox{--}6.95$ . We observe the longer loops at a similar temperature, albeit very feeble. Using LOS magnetograms, we conclude that the magnetic reconnection may have caused the transient. Our observations further suggest that the physics of the formation of such transients may be similar to those of typical coronal jets, albeit in different topological configurations. Such multiwavelength observations shed light on the formation of hot plasma in the solar corona and provide further essential constraints on modeling the thermodynamics of such transients.

Keywords: Solar flares, Solar active region filaments, Solar coronal heating, Active sun, Solar active regions
A ΔR ∼ 9.5 mag Superflare of an Ultracool Star Detected by the SVOM/GWAC System. We report the detection and follow-up of a superstellar flare GWAC 181229A with an amplitude of ΔR ∼ 9.5 mag on an M9-type star by SVOM/GWAC and the dedicated follow-up telescopes. The estimated bolometric energy Ebol is (5.56-9.25) × 1034 erg, which makes the event one of the most powerful flares seen on ultracool stars. The magnetic strength is inferred to be 3.6-4.7 kG. Thanks to sampling with a cadence of 15 s, a new component near the peak time with a very steep decay is detected in the R-band light curve, followed by the two-component flare template given by Davenport et al. An effective temperature of 5340 ± 40 K is measured by fitting a blackbody shape to the spectrum in the shallower phase during the flare. The filling factors of the flare are estimated to be ∼30% and 19% at the peak time and at 54 minutes after the first detection. The detection of this particular event with large amplitude, huge emitted energy, and a new component demonstrates that high-cadence sky monitoring cooperation with fast follow-up observations is very important for understanding the violent magnetic activity.

Keywords: M dwarf stars, Stellar flares, Spectroscopy, Flare stars
Rigorous Theory for Secondary Cosmic-Ray Ionization. The energy spectrum of electrons produced in molecular gas by interstellar cosmic rays (CRs) is rigorously calculated as a function of gas column density N traversed by the CRs. This allows us to accurately compute the local value of the secondary ionization rate of molecular hydrogen, ${\zeta }_{\sec }(N)$ , as a function of the local primary ionization rate, ζp(N). The ratio ${\zeta }_{\sec }/{\zeta }_{p}$ increases monotonically with N, and can considerably exceed the value of ≈0.67 commonly adopted in the literature. For sufficiently soft interstellar spectra, the dependence ${\zeta }_{\sec }/{\zeta }_{p}$ versus N is practically insensitive to their particular shape and thus is a general characteristic of the secondary CR ionization in dense gas.

Keywords: Secondary cosmic rays, Molecular clouds