Sazuna/UAT_keywords huggingface dataset:
The Host Galaxy of the Recoiling Black Hole Candidate in 3C 186: An Old Major Merger Remnant at the Center of a z = 1 Cluster. 3C 186, a radio-loud quasar at z = 1.0685, was previously reported to have both velocity and spatial offsets from its host galaxy, and has been considered as a promising candidate for a gravitational wave recoiling black hole triggered by a black hole merger. Another possible scenario is that 3C 186 is in an ongoing galaxy merger, exhibiting a temporary displacement. In this study, we present analyses of new deep images from the Hubble Space Telescope WFC3-IR and Advanced Camera for Surveys, aiming to characterize the host galaxy and test this alternative scenario. We carefully measure the light-weighted center of the host and reveal a significant spatial offset from the quasar core (11.1 ± 0.1 kpc). The direction of the confirmed offset aligns almost perpendicularly to the radio jet. We do not find evidence of a recent merger, such as a young starburst in disturbed outskirts, but only marginal light concentration in F160W at ~30 kpc. The host consists of mature (≳200 Myr) stellar populations and one compact star-forming region. We compare with hydrodynamical simulations and find that those observed features are consistently seen in late-stage merger remnants. Taken together, those pieces of evidence indicate that the system is not an ongoing/young merger remnant, suggesting that the recoiling black hole scenario is still a plausible explanation for the puzzling nature of 3C 186.

Keywords: Active galaxies, Gravitational waves
KLLR: A Scale-dependent, Multivariate Model Class for Regression Analysis. The underlying physics of astronomical systems govern the relation between their measurable properties. Consequently, quantifying the statistical relationships between system-level observable properties of a population offers insights into the astrophysical drivers of that class of systems. While purely linear models capture behavior over a limited range of system scale, the fact that astrophysics is ultimately scale dependent implies the need for a more flexible approach to describing population statistics over a wide dynamic range. For such applications, we introduce and implement a class of kernel localized linear regression (KLLR) models. KLLR is a natural extension to the commonly used linear models that allows the parameters of the linear model-normalization, slope, and covariance matrix-to be scale dependent. KLLR performs inference in two steps: (1) it estimates the mean relation between a set of independent variables and a dependent variable and; (2) it estimates the conditional covariance of the dependent variables given a set of independent variables. We demonstrate the model's performance in a simulated setting and showcase an application of the proposed model in analyzing the baryonic content of dark matter halos. As a part of this work, we publicly release a Python implementation of the KLLR method.

Keywords: Computational astronomy, Astrostatistics tools, Astronomy software, Astronomy data analysis, Astrostatistics
Improved Model of X-Ray Emission from Hot Accretion Flows. We have developed an improved model of X-ray emission from optically thin, two-temperature accretion flows, kerrflow, using an exact Monte Carlo treatment of global Comptonization as well as with a fully general relativistic description of both the radiative and hydrodynamic processes. It also includes pion-decay electrons, whose synchrotron emission dominates the seed photon yield at $\dot{M}/{\dot{M}}_{\mathrm{Edd}}\gtrsim 0.1$ in flows around supermassive black holes. We consider in detail the dependence of the model spectra on the black hole spin, the electron heating efficiency, the plasma magnetization, and the accretion rate, and we discuss the feasibility of constraining these parameters by analyzing X-ray spectra of nearby low-luminosity active galactic nuclei. We note some degeneracies that hinder precise estimations of these parameters when individual X-ray spectra are analyzed. These degeneracies are eliminated when several spectra from a given source are fitted jointly, which then allows us to reliably measure the model parameters. We find significant differences with previous spectral models of hot-flow emission, related with the computational methods for Comptonization. Finally, we briefly consider and discuss the dependence on the viscosity parameter and on the outflow strength.

Keywords: Accretion, X-ray active galactic nuclei, Kerr black holes
Quasiperiodic Behavior in the γ-Ray Light Curve of the Blazar PKS 0405-385. We analyze the quasiperiodic oscillation (QPO) of the historical light curve of flat-spectrum radio quasars PKS 0405-385 detected by the Fermi Large Area Telescope from 2008 August to 2021 November. To identify and determine the QPO signal of PKS 0405-385 in the γ-ray light curve, we use four time series analysis techniques based on frequency and time domains, i.e., the Lomb-Scargle periodogram (LSP), the weighted wavelet z-transform (WWZ), the REDFIT, and the epoch folding. The results show that PKS 0405-385 has a quasiperiodic behavior of ~2.8 yr with the significance of ~4.3σ in Fermi long-term monitoring. Remarkably, we also performed QPO analysis in the G-band light curve observed from 2014 October to 2021 October using LSP and WWZ technology, and the results (~4σ of significance) are consistent with the periodic detection in γ-ray. This may imply that the optical emission is radiated by an electron population in the same way as the γ-ray emission. In discussing the possible mechanism of quasiperiodic behavior, either the helical motion within a jet or the supermassive black hole binary system provides a viable explanation for the QPO of 2.8 yr, and the relevant parameters have been estimated.

Keywords: Blazars, Flat-spectrum radio quasars, Period search
Radical Recombination during the Phase Transition of Interstellar CO Ice. Complex organic molecules (COMs) can be produced efficiently in ice mixtures that simulate the ice mantle on cosmic dust grains, according to prior experimental studies. However, the mechanism that brings the reactive species together in the ice has been debated. Thermal diffusion, which is widely regarded as the main mechanism to bring reactants together, is inefficient at a typical dense cloud temperature of 10 K. A recent experimental study found that the transition of a thin CO ice film from the amorphous to crystalline phase happens at about 10 K. When a small fraction of CO2 was mixed with CO, the CO2 molecules can separate and form clusters during CO phase transition. It was further proposed that the separation of minor species in the CO ice during phase transition may be an important mechanism to form interstellar COMs without the need for thermal diffusion. In this study, we try to verify this new mechanism through laboratory experiments. An ice mixture of CH3OH and CO, which is an analog of the outer layer of the ice mantle on cosmic dust grains, was exposed to UV irradiation to produce radicals such as HCO and CH2OH, whose concentration was monitored during the subsequent warm-up of the ice. We find clear evidence that during the CO phase transition, most of the radicals recombine to form other molecular species, therefore supporting the recently proposed mechanism of COM formation via CO phase transition.

Keywords: Interstellar dust, Interstellar molecules, Laboratory astrophysics, Dense interstellar clouds
GRB 200826A: A Precursor of a Long Gamma-Ray Burst with Missing Main Emission. The recently discovered peculiar gamma-ray burst GRB 200826A poses a dilemma for the collapsar model. Although all other characteristics of the burst are consistent with it being a Type II (i.e., collapse of a massive star) event, the observed duration of the event is only approximately 1 s, which is at odds with the predicted allowable timescale range for a collapsar event. To resolve this dilemma, this Letter proposes that the original burst could be an intrinsically long GRB comprising a precursor and a main emission phase. However, the main emission phase is missed due to either precession of the jet or the obstruction by a companion star, leaving only the precursor observed as a short-duration GRB 200826A. Interestingly, we found that the temporal and spectral properties of GRB 200826A broadly resembled those of the bright precursor observed in GRB 160625B. Furthermore, assuming the prototype burst of GRB 200826A is similar to that of GRB 160625B, we found that the observer may indeed miss its main emission because of geometric effects caused either by jet precession or companion-obstruction models. Our approach provides a natural explanation for the GRB 200826A-like bursts and agrees with the rarity of those events.

Keywords: Gamma-ray bursts
Is the Black-widow Pulsar PSR J1555-2908 in a Hierarchical Triple System?. The 559 Hz black-widow pulsar PSR J1555-2908, originally discovered in radio, is also a bright gamma-ray pulsar. Timing its pulsations using 12 yr of Fermi-Large Area Telescope gamma-ray data reveals long-term variations in its spin frequency that are much larger than is observed from other millisecond pulsars. While this variability in the pulsar rotation rate could be intrinsic "timing noise," here we consider an alternative explanation: the variations arise from the presence of a very-low-mass third object in a wide multiyear orbit around the neutron star and its low-mass companion. With current data, this hierarchical-triple-system model describes the pulsar's rotation slightly more accurately than the best-fitting timing noise model. Future observations will show if this alternative explanation is correct.

Keywords: Gamma-ray sources, Pulsar planets, Pulsar timing method, Millisecond pulsars
A New Method for Measuring Infrared Band Strengths in H<SUB>2</SUB>O Ices: First Results for OCS, H<SUB>2</SUB>S, and SO<SUB>2</SUB>. Infrared (IR) band strengths are needed to extract accurate molecular abundances from astronomical observations of interstellar and solar system ices. However, laboratory measurements of such intensities often have required multiple assumptions about ice composition and thickness. Here we describe a method that circumvents most of the common assumptions and uncertainties in IR band-strength determinations. We have applied the method to measure IR band strengths of OCS, H2S, and SO2 in the absence and presence of H2O ice at 10 K, the first measurements of their type. Our results show for the first time that the presence of H2O makes little difference in IR intensities for these three sulfur-containing molecules' strongest IR features. The immediate application will be to laboratory studies of low-temperature chemistry of interstellar and cometary ices.

Keywords: Interstellar molecules, Laboratory astrophysics, Chemical abundances, Astrochemistry
ALMA Survey of Orion Planck Galactic Cold Clumps (ALMASOP): Deriving Inclination Angle and Velocity of the Protostellar Jets from Their SiO Knots. We have selected six sources (G209.55-19.68S2, G205.46-14.56S1-A, G203.21-11.20W2, G191.90-11.21S, G205.46-14.56S3, and G206.93-16.61W2) from the Atacama Large Millimeter/submillimeter Array Survey of Orion Planck Galactic Cold Clumps (ALMASOP), in which these sources have been mapped in the CO (J = 2-1), SiO (J = 5-4), and C18O (J = 2-1) lines. These sources have high-velocity SiO jets surrounded by low-velocity CO outflows. The SiO jets consist of a chain of knots. These knots have been thought to be produced by semiperiodic variations in jet velocity. Therefore, we adopt a shock-forming model, which uses such variations to estimate the inclination angle and velocity of the jets. We also derive the inclination angle of the CO outflows using the wide-angle wind-driven shell model and find it to be broadly consistent with that of the associated SiO jets. In addition, we apply this shock-forming model to another three protostellar sources with SiO jets in the literature-HH 211, HH 212, and L1448C(N)-and find that their inclination angle and jet velocity are consistent with those previously estimated from proper-motion and radial-velocity studies.

Keywords: Stellar jets, Young stellar objects, Stellar winds, Star formation, Shocks
From Pericenter and Back: Full Debris Stream Evolution in Tidal Disruption Events. When a star passes too close to a supermassive black hole, it gets disrupted by strong tidal forces. The stellar debris then evolves into an elongated stream of gas that partly falls back toward the black hole. We present an analytical model describing for the first time the full stream evolution during such a tidal disruption event (TDE). Our framework consists of dividing the stream into different sections of elliptical geometry, whose properties are independently evolved in their comoving frame under the tidal, pressure, and self-gravity forces. Through an explicit treatment of the tidal force and the inclusion of the gas angular momentum, we can accurately follow the stream evolution near pericenter. Our model evolves the longitudinal stream stretching and both transverse widths simultaneously. For the latter, we identify two regimes depending on whether the dynamics is entirely dominated by the tidal force (ballistic regime) or additionally influenced by pressure and self-gravity (hydrostatic regime). We find that the stream undergoes transverse collapses both shortly after the stellar disruption and upon its return near the black hole, at specific locations determined by the regime of evolution considered. The stream evolution predicted by our model can be used to determine the subsequent interactions experienced by this gas that are at the origin of most of the electromagnetic emission from TDEs. Our results suggest that the accretion disk may be fed at a rate that differs from the standard fallback rate, which would provide novel observational signatures dependent on black hole spin.

Keywords: Black hole physics, Hydrodynamics, Galaxy nuclei
Looking at the Distant Universe with the MeerKAT Array: Discovery of a Luminous OH Megamaser at z &gt; 0.5. In the local universe, OH megamasers (OHMs) are detected almost exclusively in infrared-luminous galaxies, with a prevalence that increases with IR luminosity, suggesting that they trace gas-rich galaxy mergers. Given the proximity of the rest frequencies of OH and the hyperfine transition of neutral atomic hydrogen (H I), radio surveys to probe the cosmic evolution of H I in galaxies also offer exciting prospects for exploiting OHMs to probe the cosmic history of gas-rich mergers. Using observations for the Looking At the Distant Universe with the MeerKAT Array (LADUMA) deep H I survey, we report the first untargeted detection of an OHM at z &gt; 0.5, LADUMA J033046.20-275518.1 (nicknamed "Nkalakatha"). The host system, WISEA J033046.26-275518.3, is an infrared-luminous radio galaxy whose optical redshift z ≈ 0.52 confirms the MeerKAT emission-line detection as OH at a redshift z OH = 0.5225 ± 0.0001 rather than H I at lower redshift. The detected spectral line has 18.4σ peak significance, a width of 459 ± 59 km s-1, and an integrated luminosity of (6.31 ± 0.18 [statistical] ± 0.31 [systematic]) × 103 L ⊙, placing it among the most luminous OHMs known. The galaxy's far-infrared luminosity L FIR = (1.576 ±0.013) × 1012 L ⊙ marks it as an ultraluminous infrared galaxy; its ratio of OH and infrared luminosities is similar to those for lower-redshift OHMs. A comparison between optical and OH redshifts offers a slight indication of an OH outflow. This detection represents the first step toward a systematic exploitation of OHMs as a tracer of galaxy growth at high redshifts.

Keywords: Starburst galaxies, Hydroxyl masers, Radio loud quasars, Megamasers, Galaxy mergers, Ultraluminous infrared galaxies
Spatially Resolved Moving Radio Burst Associated with an EUV Wave. Coronal mass ejections (CMEs) are large clouds of magnetized plasma ejected from the Sun and are often associated with the acceleration of electrons that can result in radio emission via various mechanisms. However, the underlying mechanism relating the CMEs and particle acceleration still remains a subject of heated debate. Here, we report multi-instrument radio and extreme ultraviolet (EUV) imaging of a solar eruption event on 2011 September 24. We determine the emission mechanism of a moving radio burst, identify its three-dimensional location with respect to a rapidly expanding EUV wave, and find evidence for CME shocks that produce quasiperiodic acceleration of electron beams.

Keywords: Radio bursts, Solar particle emission, Solar coronal mass ejections
A Tentative 114 minute Orbital Period Challenges the Ultracompact Nature of the X-Ray Binary 4U 1812-12. We present a detailed time-resolved photometric study of the ultracompact X-ray binary candidate 4U 1812-12. The multicolor light curves obtained with HiPERCAM on the 10.4 m Gran Telescopio Canarias show a ≃114 minute modulation similar to a superhump. Under this interpretation, this period should lie very close to the orbital period of the system. Contrary to what its other observational properties suggest (namely, persistent dim luminosity, low optical-to-X-ray flux ratio, and lack of hydrogen features in the optical spectrum), this implies that 4U 1812-12 is most likely not an ultracompact X-ray binary, which is usually defined as a system with an orbital period lower than 80 minutes. We discuss the nature of the system, showing that a scenario in which 4U 1812-12 is the progenitor of an ultracompact X-ray binary may reconcile all the observables.

Keywords: Stellar accretion disks, Neutron stars, Low-mass x-ray binary stars
Spectra of Magnetic Turbulence in a Relativistic Plasma. We present a phenomenological and numerical study of strong Alfvénic turbulence in a magnetically dominated collisionless relativistic plasma with a strong background magnetic field. In contrast with the nonrelativistic case, the energy in such turbulence is contained in magnetic and electric fluctuations. We argue that such turbulence is analogous to turbulence in a strongly magnetized nonrelativistic plasma in the regime of broken quasi-neutrality. Our 2D particle-in-cell numerical simulations of turbulence in a relativistic pair plasma find that the spectrum of the total energy has the scaling k -3/2, while the difference between the magnetic and electric energies, the so-called residual energy, has the scaling k -2.4. The electric and magnetic fluctuations at scale ℓ exhibit dynamic alignment with the alignment angle scaling close to $\cos {\phi }_{{\ell }}\propto {{\ell }}^{1/4}$ . At scales smaller than the (relativistic) plasma inertial scale, the energy spectrum of relativistic inertial Alfvén turbulence steepens to k -3.5.

Keywords: Plasma astrophysics, Relativistic fluid dynamics
On the Connection between Supermassive Black Holes and Galaxy Growth in the Reionization Epoch. The correlation between the mass of supermassive black holes (SMBHs; ${{ \mathcal M }}_{\mathrm{BH}}$ ) and their host galaxies ( ${{ \mathcal M }}_{\star }$ ) in the reionization epoch provides valuable constraints on their early growth. High-redshift quasars typically have an ${{ \mathcal M }}_{\mathrm{BH}}$ / ${{ \mathcal M }}_{\star }$ ratio significantly elevated in comparison to the local value. However, the degree to which this apparent offset is driven by observational biases is unclear for the most distant quasars. To address this issue, we model the sample selection and measurement biases for a compilation of 20 quasars at z ~ 6 with host properties based on ALMA observations. We find that the observed distribution of quasars in the ${{ \mathcal M }}_{\mathrm{BH}}\mbox{--}{{ \mathcal M }}_{\star }$ plane can be reproduced by assuming that the underlying SMBH population at z ~ 6 follows the relationship in the local universe. However, a positive or even a negative evolution in ${{ \mathcal M }}_{\mathrm{BH}}$ / ${{ \mathcal M }}_{\star }$ can also explain the data, depending on whether the intrinsic scatter evolves and on the strength of various systematic uncertainties. To break these degeneracies, an improvement in the accuracy of mass measurements and an expansion of the current sample to lower ${{ \mathcal M }}_{\mathrm{BH}}$ limits are needed. Furthermore, assuming a radiative efficiency of 0.1 and quasar duty cycles estimated from the active SMBH fraction, significant outliers in ${{ \mathcal M }}_{\mathrm{BH}}$ / ${{ \mathcal M }}_{\star }$ tend to move toward the local relation given their instantaneous BH growth rate and star formation rate. This may provide evidence for a self-regulated SMBH-galaxy coevolution scenario that is in place at z ~ 6, with active galactic nucleus feedback being a possible driver.

Keywords: AGN host galaxies, Supermassive black holes, Quasars, Active galactic nuclei, Galaxy evolution
On the Single-event-based Identification of Primordial Black Hole Mergers at Cosmological Distances. The existence of primordial black holes (PBHs), which may form from the collapse of matter overdensities shortly after the Big Bang, is still under debate. Among the potential signatures of PBHs are gravitational waves (GWs) emitted from binary black hole (BBH) mergers at redshifts z ≳ 30, where the formation of astrophysical black holes is unlikely. Future ground-based GW detectors, the Cosmic Explorer and Einstein Telescope, will be able to observe equal-mass BBH mergers with total mass of ${ \mathcal O }(10\mbox{--}100)\,{M}_{\odot }$ at such distances. In this work, we investigate whether the redshift measurement of a single BBH source can be precise enough to establish its primordial origin. We simulate BBHs of different masses, mass ratios and orbital orientations. We show that for BBHs with total masses between 20 M ⊙ and 40 M ⊙ merging at z ≥ 40, one can infer z &gt; 30 at up to 97% credibility, with a network of one Einstein Telescope, one 40 km Cosmic Explorer in the US, and one 20 km Cosmic Explorer in Australia. This number reduces to 94% with a smaller network made of one Einstein Telescope and one 40 km Cosmic Explorer in the US. We also analyze how the measurement depends on the Bayesian priors used in the analysis and verify that priors that strongly favor the wrong model yield smaller Bayesian evidences.

Keywords: Stellar mass black holes, Gravitational waves, Primordial black holes, Astrophysical black holes
The Timing of Potential Last Nucleosynthetic Injections into the Protosolar Molecular Cloud Inferred from <SUP>41</SUP>Ca-<SUP>26</SUP>Al Systematics of Bulk CAIs. Short-lived radionuclides (SLRs) provide important information about the chronology of the early solar system. Among them, 41Ca, due to its decay to 41K with a half-life of only 0.1 Ma, is particularly valuable in constraining the timescales and origins of both SLRs and the formation of the oldest solar system materials, the Ca-Al-rich inclusions (CAIs). The initial abundance of 41Ca in the solar system, expressed as the (41Ca/40Ca)I ratio, is the key to unveiling the origin of this nuclide. Here, we report a new solar system (41Ca/40Ca)I ratio of 2.0 × 10-8 derived from the K isotope compositions of two CAIs. This new ratio is about four times higher than the previous value inferred from a mineral isochron. Such a high (41Ca/40Ca)I ratio in the CAIs exceeds that expected for the protosolar molecular cloud by ~1000×, implying very late injection of the 41Ca (and possibly other SLRs) into the protosolar molecular cloud. The correlated enrichments of 41Ca and 26Al in the bulk CAI samples hint at a common stellar origin of both SLRs. The injection time estimated from our new data depends on the stellar source-it ranges from 0.6 Ma for a Wolf-Rayet wind to 1.0 Ma for a TP-AGB star ejecta.

Keywords: Cosmochemistry, Nucleosynthesis, Solar system