Sazuna/UAT_keywords huggingface dataset:
The Star-forming Main Sequence and the Contribution of Dust-obscured Star Formation since z ∼ 4 from the Far-UV+IR Luminosity Functions. An analytical approach is proposed to study the evolution of the star-forming galaxy (SFG) main sequence (MS) and the fraction of dust-obscured star formation (SF) up to z ∼ 4. Far-ultraviolet (FUV) and infrared (IR) star formation rates (SFRs) are described as conditional probability functions of M*. We convolve them with the galaxy stellar mass function (GSMF) of SFGs to derive the FUV and IR luminosity functions (LFs). The two SF modes formalism is used to describe starburst galaxies. By fitting observed FUV and IR LFs, the parameterization of SFRFUV-M* and SFRIR- M* is constrained. Our derived SFRFUV+IR-M* reproduces the evolution of the MS as compared to other observational inferences. At any redshift, we find that the sSFRFUV+IR-M* relation for MS SFGs approaches a power law at the high-mass end. At lower masses, it bends, and eventually, the slope sign changes from negative to positive at very low masses. At z ∼ 0, this change of sign is at M* ∼ 5 × 108 M⊙, close to the dust-obscured SF regime, M* ∼ 6 × 108 M⊙. The slope sign change is related to the knee of the FUV LF. Our derived dust-obscured fractions agree with previous determinations at 0 ≤ z ≤ 2.5. Dust-obscured fractions depend strongly on mass with almost no dependence on redshift at z ≳ 1.2. At z ≲ 0.75, high-mass galaxies become more "transparent" compared to their high-redshift counterparts. On the other hand, low- and intermediate-mass galaxies have become more obscured by dust. The joint evolution of the GSMF and the FUV and IR LFs is a promising approach to study mass growth and dust formation/destruction mechanisms.

Keywords: Galaxy abundances, Galaxy evolution, Galaxy processes, Galaxy counts
Application of Convolutional Neural Networks to Identify Protostellar Outflows in CO Emission. We adopt the deep learning method CASI-3D (Convolutional Approach to Structure Identification-3D) to identify protostellar outflows in molecular line spectra. We conduct magnetohydrodynamics simulations that model forming stars that launch protostellar outflows and use these to generate synthetic observations. We apply the 3D radiation transfer code RADMC-3D to model 12CO (J = 1-0) line emission from the simulated clouds. We train two CASI-3D models: ME1 is trained to predict only the position of outflows, while MF is trained to predict the fraction of the mass coming from outflows in each voxel. The two models successfully identify all 60 previously visually identified outflows in Perseus. Additionally, CASI-3D finds 20 new high-confidence outflows. All of these have coherent high-velocity structure, and 17 of them have nearby young stellar objects, while the remaining three are outside the Spitzer survey coverage. The mass, momentum, and energy of individual outflows in Perseus predicted by model MF is comparable to the previous estimations. This similarity is due to a cancellation in errors: previous calculations missed outflow material with velocities comparable to the cloud velocity; however, they compensate for this by overestimating the amount of mass at higher velocities that has contamination from nonoutflow gas. We show that outflows likely driven by older sources have more high-velocity gas compared to those driven by younger sources.

Keywords: Stellar jets, Convolutional neural networks, Astronomy data analysis, Molecular clouds, Star formation, Interstellar medium
A Population of Compact Radio Variables and Transients in the Radio-bright Zone at the Galactic Center Observed with the Jansky Very Large Array. Using Jansky Very Large Array data obtained from high-resolution observations at 5.5 GHz at multiple epochs in 2014 and 2019, we have detected a population of radio variables and transients in the radio-bright zone at the Galactic center. With observations covering a sky area of 180 arcmin2 at an angular resolution of 0"4, we report new detections of 110 Galactic center compact radio (GCCR) sources with a size of &lt;1″. The flux densities of GCCR sources exceed 70 μJy, with at least 10σ significance. Among these sources, 82 are variable or transient and 28 are nonvariable. About 10% of them are expected to be extragalactic background sources. We discuss the possible astrophysical nature of the detected sources. As compared to the Galactic disk (GD) population of normal pulsars (NPs) and millisecond pulsars (MSPs), a majority (80%) of the GCCR sources appear to fall within the high flux density tail of the pulsar distribution, as extrapolated from a sample of NPs in the GD. However, MSPs extrapolated from the GD population are too weak to have contributed significantly to the GCCR population that has been detected. We also cross-correlated the GCCR sources with X-ray sources in Chandra X-ray catalogs and found that 42 GCCR sources have candidate X-ray counterparts. Most of the GCCR sources having X-ray counterparts are likely to be associated with unresolved or slightly resolved radio jets launched from X-ray binaries with a compact object, either a black hole or a neutron star.

Keywords: Neutron stars, Galactic center, Radio transient sources, Black holes, Millisecond pulsars, White dwarf stars, Radio continuum emission, Interstellar medium, Discrete radio sources, Radio interferometry, Radio pulsars
Testing Disk Identification Methods through Numerical Simulations of Protostellar Evolution. We test whether the radii of circumstellar disks can be reliably determined in observations by applying the results of a numerical simulation. First, we execute a core-collapse simulation, which starts from a rotating magnetized spherical core, and continue the calculation until the protostellar mass reaches 0.5 M⊙. Then, for each set of simulation data, we calculate the radiative transfer to generate the data cube for the synthetic observation. The spatial and velocity resolutions of the synthetic observation are 0"15 (20 au) and 0.1 km s-1, respectively. We define seven different disk radii. Four radii are estimated from the synthetic observation, using the continuum image, continuum visibility, C18O channel map, and C18O position-velocity (PV) diagram. The other three radii are taken from the simulation and use the disk rotation, infall motion, and density contrast around the protostar to identify the disk. Finally, we compare the disk radii estimated from the systemic observation with those from the simulation. We find that the disk radius defined using the PV diagram can reliably trace the Keplerian disk when the protostellar mass is larger than M* ≳ 0.2 M⊙, independent of the inclination angle to the line of sight. In addition, the PV diagram provides an accurate estimate of the central stellar mass through the whole protostellar evolution. The simulation also indicates that the circumstellar disk is massive enough to be gravitationally unstable through the evolution. Such an unstable disk can show either a circular or spiral morphology on a similar timescale.

Keywords: Low mass stars, Protostars, Protoplanetary disks, Magnetohydrodynamical simulations
Constraints on the Abundance of 0.01 c Stellar Engines in the Milky Way. Stellar engines are hypothesized megastructures that extract energy from the host star, typically with the purpose of generating thrust and accelerating the stellar system. We explore the maximum potential speeds that could be realizable by stellar engines, and determine that speeds up to ∼0.1 c might perhaps be attainable under optimal conditions. In contrast, natural astrophysical phenomena in the Milky Way are very unlikely to produce such speeds. Hence, astrometric surveys of hypervelocity stars may be utilized to conduct commensal searches for high-speed stellar engines in the Milky Way. It may be possible to derive bounds on their abundance, but this requires certain assumptions regarding the spatiotemporal distribution of such engines, which are not guaranteed to be valid.

Keywords: Surveys, Technosignatures, Astrobiology, Astrometry, Search for extraterrestrial intelligence
Constraining the Halo Mass of Damped Lyα Absorption Systems (DLAs) at z = 2-3.5 Using the Quasar-CMB Lensing Cross-correlation. We study the cross-correlation of damped Lyα systems (DLAs) and their background quasars, using the most updated DLA catalog and the Planck 2018 CMB lensing convergence field. Our measurement suggests that the DLA bias ${b}_{\mathrm{DLA}}$ is smaller than 3.1, corresponding to $\mathrm{log}(M/{M}_{\odot }{h}^{-1})\leqslant 12.3$ at a confidence of 90%. These constraints are broadly consistent with Alonso et al. and previous measurements by cross-correlation between DLAs and the Lyα forest (e.g., Font-Ribera et al.; Prez-Rfols et al.). Further, our results demonstrate the potential of obtaining a more precise measurement of the halo mass of the high-redshift sources using next generation CMB experiments with a higher angular resolution. The python-based codes and data products of our analysis are available at https://github.com/LittleLin1999/CMB-lensingxDLA.

Keywords: Galaxy dark matter halos, Large-scale structure of the universe, Quasars, Cosmic microwave background radiation, Damped Lyman-alpha systems, Intergalactic medium
Orbital Distribution of Infalling Satellite Halos across Cosmic Time. The initial orbits of infalling subhalos largely determine the subsequent evolution of the subhalos and satellite galaxies therein and shed light on the assembly of their hosts. Using a large set of cosmological simulations of various resolutions, we quantify the orbital distribution of subhalos at infall time and its mass and redshift dependence in a large dynamic range. We further provide a unified and accurate model validated across cosmic time, which can serve as the initial condition for semianalytic models. We find that the infall velocity v follows a nearly universal distribution peaked near the host virial velocity Vh for any subhalo mass or redshift, while the infall orbit is most radially biased when v ∼ Vh. Moreover, subhalos that have a higher host mass or a higher sub-to-host ratio tend to move along a more radial direction with a relatively smaller angular momentum than their low host mass or low sub-to-host ratio counterparts, though they share the same normalized orbital energy. These relations are nearly independent of the redshift when using the density peak height as the proxy for host halo mass. The above trends are consistent with the scenario where the dynamical environment is relatively colder for more massive structures because their own gravity is more likely to dominate the local potentials. Based on this understanding, the more massive or isolated halos are expected to have higher velocity anisotropy.

Keywords: Galaxy dark matter halos, Galaxy formation, Large-scale structure of the universe, Galaxy dynamics, Astrostatistics, Galaxy kinematics, N-body simulations, Dark matter
Hadronic High-energy Emission from Magnetically Arrested Disks in Radio Galaxies. We propose a novel interpretation that gamma rays from nearby radio galaxies are hadronic emission from magnetically arrested disks (MADs) around central black holes (BHs). The magnetic energy in MADs is higher than the thermal energy of the accreting plasma, where the magnetic reconnection or turbulence may efficiently accelerate nonthermal protons. They emit gamma rays via hadronic processes, which can account for the observed gamma rays for M87 and NGC 315. Nonthermal electrons are also accelerated with protons and produce MeV gamma rays, which is useful to test our model by proposed MeV satellites. The hadronic emission from the MADs may significantly contribute to the GeV gamma-ray background and produce the multi-PeV neutrino background detectable by IceCube-Gen2. In addition, gamma rays from MADs provide electron-positron pairs through two-photon pair production at the BH magnetosphere. These pairs can screen the vacuum gap, which affects high-energy emission and jet-launching mechanisms in radio galaxies.

Keywords: Accretion, Low-luminosity active galactic nuclei, Non-thermal radiation sources, Cosmic background radiation, Radio active galactic nuclei, Gamma-rays
On the Existence of Shear-current Effects in Magnetized Burgulence. The possibility of explaining shear flow dynamos by a magnetic shear-current (MSC) effect is examined via numerical simulations. Our primary diagnostics is the determination of the turbulent magnetic diffusivity tensor η. In our setup, a negative sign of its component ηyx is necessary for coherent dynamo action by the SC effect. To be able to measure turbulent transport coefficients from systems with magnetic background turbulence, we present an extension of the test-field method (TFM) applicable to our setup where the pressure gradient is dropped from the momentum equation: the nonlinear TFM (NLTFM). Our momentum equation is related to Burgers' equation and the resulting flows are referred to as magnetized burgulence. We use both stochastic kinetic and magnetic forcings to mimic cases without and with simultaneous small-scale dynamo action. When we force only kinetically, negative ηyx are obtained with exponential growth in both the radial and azimuthal mean magnetic field components. Using magnetokinetic forcing, the field growth is no longer exponential, while NLTFM yields positive ηyx. By employing an alternative forcing from which wavevectors whose components correspond to the largest scales are removed, the exponential growth is recovered, but the NLTFM results do not change significantly. Analyzing the dynamo excitation conditions for the coherent SC and incoherent α and SC effects shows that the incoherent effects are the main drivers of the dynamo in the majority of cases. We find no evidence for MSC-effect-driven dynamos in our simulations.

Keywords: Astrophysical magnetism, Magnetohydrodynamical simulations
Observations of Outward-propagating and Mirroring of the Same Energetic Electrons by Wind. We report an energetic electron event observed by the Wind spacecraft in which electrons were first detected to propagate away from the Sun, and subsequently detected to propagate back toward the Sun. Using the recently developed fractional velocity dispersion analysis (FVDA), the path lengths corresponding to these two sequential electron signals were found to be ∼1.5 and ∼3.1 au. The inferred release times for both populations were found to be the same, within uncertainty. No bidirectional halo electrons were identified during the event, indicating that the electrons were not propagating within a closed magnetic field configuration (e.g., a magnetic flux rope). These observations suggest that the same energetic electrons were observed twice at 1 au, with the second time being due to reflection occurring beyond 1 au, by perhaps magnetic kinks caused by a coronal mass ejection-driven shock.

Keywords: Solar energetic particles, Solar coronal mass ejection shocks, Interplanetary magnetic fields, Solar coronal mass ejections
NuSTAR Non-detection of a Faint Active Galactic Nucleus in an Ultraluminous Infrared Galaxy with Kpc-scale Fast Wind. Large-scale outflows are generally considered to be possible evidence that active galactic nuclei (AGNs) can severely affect their host galaxies. Recently, an ultraluminous infrared galaxy (ULIRG) at z = 0.49, AKARI J0916248+073034, was found to have a galaxy-scale [O III] λ5007 outflow with one of the highest energy-ejection rates at z &lt; 1.6. However, the central AGN activity estimated from its torus mid-infrared (MIR) radiation is weak relative to the luminous [O III] emission. In this work we report the first NuSTAR hard X-ray follow-up of this ULIRG to constrain its current AGN luminosity. The intrinsic 2-10 keV luminosity shows a 90% upper limit of 3.0 × 1043 erg s-1 assuming Compton-thick obscuration (NH = 1.5 × 1024 cm-2), which is only 3.6% of the luminosity expected from the extinction-corrected [O III] luminosity. Using the NuSTAR observation, we successfully identify that this ULIRG has a very extreme case of X-ray deficit among local ULIRGs. A possible scenario to explain the drastic decline in both the corona (X-ray) and torus (MIR) is that the primary radiation from the AGN accretion disk is currently in a fading status, as a consequence of a powerful nuclear wind suggested by powerful ionized outflow in a galaxy scale.

Keywords: Ultraluminous infrared galaxies, Active galaxies, X-ray active galactic nuclei
Discovery of Magellanic Stellar Debris in the H3 Survey. We report the discovery of 15 stars in the H3 survey that lie, in projection, near the tip of the trailing gaseous Magellanic Stream (MS). The stars have Galactocentric velocities &lt;-155 km s-1, Galactocentric distances of ≈40 to 80 kpc (increasing along the MS), and [Fe/H] consistent with that of stars in the Small Magellanic Cloud. These 15 stars comprise 94% (15 of 16) of the H3 observed stars to date that have RGAL &gt; 37.5 kpc, -350 km s-1 &lt; VGSR &lt; -155 km s-1, and are not associated with the Sagittarius Stream. They represent a unique portion of the Milky Way's outer halo phase space distribution function and confirm that unrelaxed structure is detectable even at radii where H3 includes only a few hundred stars. Due to their statistical excess, their close association with the MS and HI compact clouds in the same region, both in position and velocity space, and their plausible correspondence with tidal debris in a published simulation, we identify these stars as debris of past Magellanic Cloud encounters. These stars are evidence for a stellar component of the tidal debris field far from the Clouds themselves and provide unique constraints on the interaction.

Keywords: Milky Way stellar halo, Magellanic Clouds, Magellanic Stream
Observational Evidence for Fast Mode Periodic Small-scale Shocks: A New Type of Plasma Phenomenon. We show observational evidence for a new form of collisionless shock in interplanetary space near Mars, small-scale shocks with periodic spacings. Pickup of new ionized hydrogen atoms in a magnetic field aligned with the solar wind direction causes the generation of a magnetosonic wave train through an ion beam instability. The waves have a frequency close to the local proton gyrofrequency. This is a similar physical process as for the formation of cometary plasma waves/turbulence. However, for the case of proton pickup near Mars, each individual magnetosonic wave cycle develops into a small-scale shock. So there is a string of fast mode shocks formed with proton gyroperiod spacings. These small-scale shocks display dissipation in the ions and dispersive whistlers. A fraction of ions trapped/reflected at the small-scale shocks are accelerated by the motional electric field. Observational results demonstrate that periodic shocks can perform the same functions as a single supercritical shock in a high-speed flow.

Keywords: Solar coronal mass ejection shocks, Interplanetary shocks, Planetary bow shocks, Stellar bow shocks
Application of The Wind-driven Model to a Sample of Tidal Disruption Events. An origin of the optical/ultraviolet (UV) radiation from tidal disruption events (TDEs) has recently been discussed for different scenarios, but observational support is generally lacking. In this Letter, we test the applicability of the "wind-driven model" for a sample of UV/optical TDEs. With the model, we aim to derive the physical properties of the optical/UV TDEs, such as mass-loss rates and characteristic radii. The model assumes optically thick continuous outflows like stellar winds, and one key question arises: how is the wind-launched radius connected to physical processes in TDEs? Here we propose one possibility: through a comparison between the escape velocities estimated from their black hole masses and the wind velocities estimated from observed line widths, the outflow is launched from the self-interaction radius (RSI) where the stellar debris stretched by the tidal force intersects. We show that the escape velocities at RSI are roughly consistent with the wind velocities. By applying the model to a sample of optical/UV TDE candidates, we find that explosive mass ejections (≳10 M⊙ yr-1) from RSI (∼1014 cm) can explain the observed properties of TDEs around peak luminosity. We also apply the same framework to a peculiar transient, AT2018cow. This model suggests that AT2018cow is likely a TDE induced by an intermediate-mass black hole (MBH ∼ 104 M⊙).

Keywords: Tidal disruption, Transient sources, Stellar winds
Model Dependence of Bayesian Gravitational-wave Background Statistics for Pulsar Timing Arrays. Pulsar timing array (PTA) searches for a gravitational-wave background (GWB) typically include time-correlated "red" noise models intrinsic to each pulsar. Using a simple simulated PTA data set with an injected GWB signal we show that the details of the red noise models used, including the choice of amplitude priors and even which pulsars have red noise, have a striking impact on the GWB statistics, including both upper limits and estimates of the GWB amplitude. We find that the standard use of uniform priors on the red noise amplitude leads to 95% upper limits, as calculated from one-sided Bayesian credible intervals, that are less than the injected GWB amplitude 50% of the time. In addition, amplitude estimates of the GWB are systematically lower than the injected value by 10%-40%, depending on which models and priors are chosen for the intrinsic red noise. We tally the effects of model and prior choice and demonstrate how a "dropout" model, which allows flexible use of red noise models in a Bayesian approach, can improve GWB estimates throughout.

Keywords: Gravitational wave detectors, Bayesian statistics, Pulsar timing method, Millisecond pulsars, Posterior distribution, Gravitational wave astronomy, Gravitational waves, Red noise, Prior distribution, Time series analysis, Astrostatistics strategies
An 8.8 Minute Orbital Period Eclipsing Detached Double White Dwarf Binary. We report the discovery of ZTF J2243+5242, an eclipsing double white dwarf binary with an orbital period of just 8.8 minutes, the second known eclipsing binary with an orbital period of less than 10 minutes. The system likely consists of two low-mass white dwarfs and will merge in approximately 400,000 yr to form either an isolated hot subdwarf or an R Coronae Borealis star. Like its 6.91 minute counterpart, ZTF J1539+5027, ZTF J2243+5242 will be among the strongest gravitational-wave sources detectable by the space-based gravitational-wave detector the Laser Space Interferometer Antenna (LISA) because its gravitational-wave frequency falls near the peak of LISA's sensitivity. Based on its estimated distance of $d={2425}_{-114}^{+108}\,\mathrm{pc}$ , LISA should detect the source within its first few months of operation and achieve a signal-to-noise ratio of 63 ± 7 after 4 yr. We find component masses of ${M}_{A}={0.323}_{-0.047}^{+0.065}$ and ${M}_{B}={0.335}_{-0.054}^{+0.052}\,{M}_{\odot }$ , radii of ${R}_{A}={0.0298}_{-0.0012}^{+0.0013}$ and ${R}_{B}={0.0275}_{-0.0013}^{+0.0012}\,{R}_{\odot }$ , and effective temperatures of ${T}_{A}={26,300}_{-900}^{+1700}$ and ${T}_{B}={19,200}_{-900}^{+1500}\,{\rm{K}}$ . We determine all of these properties and the distance to this system using only photometric measurements, demonstrating a feasible way to estimate parameters for the large population of optically faint (r &gt; 21 mAB) gravitational-wave sources that the Vera Rubin Observatory and LISA should identify.

Keywords: White dwarf stars, Compact binary stars, Gravitational wave sources