Sazuna/UAT_keywords huggingface dataset:
Evidence for Cosmic Acceleration Is Robust to Observed Correlations between Type Ia Supernova Luminosity and Stellar Age. Type Ia supernovae (SNe Ia) are powerful standardizable candles for constraining cosmological models and provided the first evidence of the accelerated expansion of the universe. Their precision derives from empirical correlations, now measured from &gt;1000 SNe Ia, between their luminosities, light-curve shapes, colors, and most recently with the stellar mass of their host galaxy. As mass correlates with other galaxy properties, alternative parameters have been investigated to improve SN Ia standardization though none have been shown to significantly alter the determination of cosmological parameters. We re-examine a recent claim, based on 34 SN Ia in nearby passive host galaxies, of a 0.05 mag Gyr-1 dependence of standardized SN Ia luminosity on host age, which, if extrapolated to higher redshifts, would be a bias up to 0.25 mag, challenging the inference of dark energy. We reanalyze this sample of hosts using both the original method and a Bayesian hierarchical model and find after a fuller accounting of the uncertainties the significance of a dependence on age to be ≤2σ and ∼1σ after the removal of a single poorly sampled SN Ia. To test the claim that a trend seen in old stellar populations can be applied to younger ages, we extend our analysis to a larger sample that includes young hosts. We find the residual dependence of host age (after all standardization typically employed for cosmological measurements) to be consistent with zero for 254 SNe Ia from the Pantheon sample, ruling out the large but low significance trend seen in passive hosts.

Keywords: Observational cosmology, Distance indicators, Type Ia supernovae, Cosmological constant, Dark energy
Quiet-time Solar Wind Suprathermal Electrons of Different Solar Origins. The energy spectrum of solar wind strahl, halo, and superhalo electrons likely carries crucial information on their possible origin and acceleration at the Sun. Here we statistically investigate the energy spectrum of solar wind strahl/halo electrons at ∼0.1-1.5 keV and superhalo electrons at ∼20-200 keV measured by Wind/3D Plasma and Energetic Particle during quiet times from 1998 to 2014, according to the types of their Potential Field Source Surface-mapped coronal source regions (CSRs). We adopt the classification scheme developed by Zhao et al. to categorize the CSRs into four types: active region (AR), quiet Sun (QS), coronal hole (CH), and helmet-streamer associated region (HS). We find that for the quiet-time strahl, the AR and HS (QS and CH) correspond to a smaller (larger) kappa index κstrahl with the most frequent value of 7-8.5 (8.5-10) and a larger (smaller) nstrahl with the most frequent value of 0.013-0.026 cm-3 (0.006-0.0013 cm-3). For the quiet-time halo, κhalo behaves similarly to κstrahl, but nhalo appears similar among the four CSR types. For the superhalo, the AR (QS) corresponds to a larger (smaller) power-law index β with the most frequent value of 2.2-2.4 (1.8-2.0), while the HS and CH have a β not different from either the AR or QS; nsup appears similar, with the most frequent value of 3 × 10-8-3 × 10-7 cm-3, among the four CSR types. These results suggest that the strahl (superhalo) from the hotter CSRs tends to be more (less) efficiently accelerated.

Keywords: Solar physics, Solar wind, Solar particle emission
Ab Initio Horizon-scale Simulations of Magnetically Arrested Accretion in Sagittarius A* Fed by Stellar Winds. We present 3D general relativistic magnetohydrodynamic (GRMHD) simulations of the accretion flow surrounding Sagittarius A* that are initialized using larger-scale MHD simulations of the ∼30 Wolf-Rayet (WR) stellar winds in the Galactic center. The properties of the resulting accretion flow on horizon scales are set not by ad hoc initial conditions but by the observationally constrained properties of the WR winds with limited free parameters. For this initial study we assume a non-spinning black hole. Our simulations naturally produce a ∼10-8 M⊙ yr-1 accretion rate, consistent with previous phenomenological estimates. We find that a magnetically arrested flow is formed by the continuous accretion of coherent magnetic field being fed from large radii. Near the event horizon, the magnetic field is so strong that it tilts the gas with respect to the initial angular momentum and concentrates the originally quasi-spherical flow to a narrow disk-like structure. We also present 230 GHz images calculated from our simulations where the inclination angle and physical accretion rate are not free parameters but are determined by the properties of the WR stellar winds. The image morphology is highly time variable. Linear polarization on horizon scales is coherent with weak internal Faraday rotation.

Keywords: Accretion, Magnetohydrodynamics, Galactic center, Stellar winds, General relativity, Wolf-Rayet stars, Astrophysical fluid dynamics, Astrophysical black holes, Magnetohydrodynamical simulations
On the Lorentz Force and Torque of Solar Photospheric Emerging Magnetic Fields. Magnetic flux generated and intensified by the solar dynamo emerges into the solar atmosphere, forming active regions (ARs) including sunspots. Existing theories of flux emergence suggest that the magnetic flux can rise buoyantly through the convection zone but is trapped at the photosphere, while its further rising into the atmosphere resorts to the Parker buoyancy instability. To trigger such an instability, the Lorentz force in the photosphere needs to be as large as the gas pressure gradient to hold up an extra amount of mass against gravity. This naturally results in a strongly non-force-free photosphere, which is indeed shown in typical idealized numerical simulations of flux tube buoyancy from below the photosphere into the corona. Here we conduct a statistical study of the extents of normalized Lorentz forces and torques in the emerging photospheric magnetic field with a substantially large sample of Solar Dynamics Observatory/Helioseismic and Magnetic Imager vector magnetograms. We found that the photospheric field has a rather small Lorentz force and torque on average, and thus is very close to a force-free state, which is not consistent with theories as well as idealized simulations of flux emergence. Furthermore, the small extents of forces and torques seem not to be influenced by the emerging AR's size, the emergence rate, or the nonpotentiality of the field. This result puts an important constraint on future development of theories and simulations of flux emergence.

Keywords: Solar photosphere, Solar magnetic fields
GW190412 as a Third-generation Black Hole Merger from a Super Star Cluster. We explore the possibility that GW190412, a binary black hole merger with a non-equal-mass ratio and significantly spinning primary, was formed through repeated black hole mergers in a dense super star cluster. Using a combination of semianalytic prescriptions for the remnant spin and recoil kick of black hole mergers, we show that the mass ratio and spin of GW190412 are consistent with a binary black hole whose primary component has undergone two successive mergers from a population of $\sim 10{M}_{\odot }$ black holes in a high-metallicity environment. We then explore the production of GW190412-like analogs in the CMC Cluster Catalog, a grid of 148 N-body star cluster models, as well as a new model, behemoth, with nearly 107 particles and initial conditions taken from a cosmological MHD simulation of galaxy formation. We show that, if the spins of black holes born from stars are small, the production of binaries with GW190412-like masses and spins is dominated by massive super star clusters with high metallicities and large central escape speeds. While many are observed in the local universe, our results suggest that a careful treatment of these massive clusters, many of which may have been disrupted before the present day, is necessary to characterize the production of unique gravitational-wave events produced through dynamics.

Keywords: Globular star clusters, Stellar mergers, Stellar mass black holes, Gravitational wave sources, Astrophysical black holes, Star clusters
Constraints on Compact Dark Matter with Fast Radio Burst Observations. Fast radio bursts (FRBs) are bright radio transients with millisecond duration at cosmological distances. Since compact dark matter/objects (COs) could act as lenses and cause splitting of these kinds of very short duration signals, Muñoz et al. have proposed a novel method to probe COs with lensing of FRBs. In this Letter, we for the first time apply this method to real data and give constraints of the nature of COs with currently available FRB observations. We emphasize that the information from dynamic spectra of FRBs is quite necessary for identifying any lensed signals and find no echoes in the existing data. The null search gives a constraint comparable to that from galactic wide binaries, though the methods of redshift inference from the dispersion measure would impact a little. Furthermore, we make an improved forecast based on the distributions of real data for the ongoing and upcoming telescopes. Finally, we discuss the situation where one or more lensed signals will be detected. In such a case, the parameter space of COs can be pinned down very well since the lens mass can be directly determined through the observed flux ratio and time delay between split images.

Keywords: Gravitational lensing, Dark matter
Magnetic Field Generation by an Inhomogeneous Return Current. A new generation mechanism of the magnetic field in an inhomogeneous collisionless plasma with a beam component is proposed. We show that even though the current and charge neutralities are initially satisfied, the current neutrality is eventually violated if there is an inhomogeneity, so that the magnetic field is generated. By conducting ab initio two-dimensional particle-in-cell simulations, we demonstrate that the magnetic field is generated as expected. The new generation mechanism of the magnetic field can play an important role in the current universe because cosmic rays can be regarded as the beam component in the astrophysical plasma. We propose that the first cosmic rays generate the magnetic field with a large scale at the redshift of z ≈ 20.

Keywords: Galaxy magnetic fields, Plasma physics, Astrophysical magnetism, Plasma astrophysics, Interstellar magnetic fields, Cosmic magnetic fields theory, Magnetic fields, Cosmic rays
Supernova Siblings: Assessing the Consistency of Properties of Type Ia Supernovae that Share the Same Parent Galaxies. While many studies have shown a correlation between properties of the light curves of SNe Ia and properties of their host galaxies, it remains unclear what is driving these correlations. We introduce a new direct method to study these correlations by analyzing "parent" galaxies that host multiple SNe Ia "siblings." Here, we search the Dark Energy Survey SN sample, one of the largest samples of discovered SNe, and find eight galaxies that hosted two likely SNe Ia. Comparing the light-curve properties of these SNe and recovered distances from the light curves, we find no better agreement between properties of SNe in the same galaxy as any random pair of galaxies, with the exception of the SN light-curve stretch. We show at 2.8σ significance that at least one-half of the intrinsic scatter of SNe Ia distance modulus residuals is not from common host properties. We also discuss the robustness with which we could make this evaluation with LSST, which will find 100× more pairs of galaxies, and pave a new line of study on the consistency of SNe Ia in the same parent galaxies. Finally, we argue that it is unlikely that some of these SNe are actually single, lensed SN with multiple images.

Keywords: Observational cosmology
Hemispheric Handedness in the Galactic Synchrotron Polarization Foreground. The large-scale magnetic field of the Milky Way is thought to be created by an αΩ dynamo, which implies that it should have opposite handedness north and south of the Galactic midplane. Here we attempt to detect a variation in handedness using polarization data from the Wilkinson Microwave Anisotropy Probe. Previous analyzes of the parity-even and parity-odd parts of linear polarization of the global dust and synchrotron emission have focused on quadratic correlations in spectral space of, and between, these two components. Here, by contrast, we analyze the parity-odd polarization itself and show that it has, on average, opposite signs in northern and southern Galactic hemispheres. Comparison with a Galactic mean-field dynamo model shows broad qualitative agreement and reveals that the sign of the observed hemispheric dependence of the azimuthally averaged parity-odd polarization is not determined by the sign of α, but by the sense of differential rotation.

Keywords: Galaxy magnetic fields
On the Metamorphosis of the Bailey Diagram for RR Lyrae Stars. We collected over 6000 high-resolution spectra of four dozen field RR Lyrae (RRL) variables pulsating either in the fundamental (39 RRab) or in the first overtone (9 RRc) mode. We measured radial velocities (RVs) of four strong metallic and four Balmer lines along the entire pulsational cycle and derived RV amplitudes with accuracies better than 1-2 km s-1. The new amplitudes were combined with literature data for 23 RRab and 3 RRc stars (total sample of 74 RRLs), which allowed us to investigate the variation of the Bailey diagram (photometric amplitude versus period) when moving from optical to mid-infrared bands and to recast the Bailey diagram in terms of RV amplitudes. We found that RV amplitudes for RRab are minimally affected by nonlinear phenomena (shocks) and multiperiodicity (Blazhko effect). The RV slope (logP-A(Vr)) when compared with the visual slope (logP-A(V)) is shallower, and the dispersion, at fixed period, decreases by a factor of two. We constructed homogeneous sets of horizontal branch evolutionary models and nonlinear, convective pulsation models of RRLs to constrain the impact of evolutionary effects on their pulsation properties. Evolution causes, on the Bailey diagram based on RV amplitudes, a modest variation in pulsation period and a large dispersion in amplitude. The broad dispersion in period of the Bailey diagram is mainly caused by variation in RRL intrinsic parameters (stellar mass, chemical composition). Empirical evidence indicates that RV amplitudes are an optimal diagnostic for tracing the mean effective temperature across the RRab instability strip.

Keywords: Stellar oscillations, Horizontal branch stars, Radial velocity, RR Lyrae variable stars
The Effect of Substellar Continent Size on Ocean Dynamics of Proxima Centauri b. The potential habitability of tidally locked planets orbiting M-dwarf stars has been widely investigated in recent work, typically with a nondynamic ocean and without continents. On Earth, ocean dynamics are a primary means of heat and nutrient distribution. Continents are a critical source of nutrients, strongly influence ocean dynamics, and participate in climate regulation. In this work, we investigate how the size of a substellar land mass affects the oceans ability to transport heat and upwell nutrients on the tidally locked planet Proxima Centauri b using the ROCKE-3D coupled ocean-atmosphere general circulation model (GCM). We find that dayside ice-free ocean and nutrient delivery to the mixed layer via upwelling are maintained across all continent sizes. We also find that Proxima Centauri b's climate is more sensitive to differences among atmospheric GCMs than to the inclusion of ocean dynamics in ROCKE-3D. Finally, we find that Proxima Centauri b transitions from a "lobster" state where ocean heat transport distributes heat away from the substellar point to an "eyeball" state where heat transport is restricted and surface temperature decreases symmetrically from the substellar point when the continent size exceeds ∼20% of the surface area. Our work suggests that both a dynamic ocean and continents are unlikely to decrease the habitability prospects of nearby tidally locked targets like Proxima Centauri b that could be investigated with future observations by the James Webb Space Telescope.

Keywords: Astrobiology, Habitable planets, Exoplanets
Bridging between the Integrated and Resolved Main Sequence of Star Formation. The position of galaxies on the stellar mass, star formation rate (SFR) plane with respect to the star-forming main sequence at each redshift is a convenient way to infer where the galaxy is in its evolution compared to the rest of the population. We use Hubble Space Telescope high-resolution images in the GOODS-S field from the the Cosmic Assembly Near-IR Deep Extragalactic Legacy Survey (CANDELS) and fit multiwavelength lights in resolution elements of galaxies with stellar population synthesis models. We then construct resolved kpc-scale stellar mass, SFR surface density curves for galaxies at z ∼ 1. Fitting these resolved main sequence curves with Schechter functions, we parameterize and explain the multiwavelength structure of galaxies with three variables: φ*, α, and M*. For quenched galaxies below the main sequence, we find an average high-mass slope (α) of the resolved main sequence curves to be ∼-0.4. The scatter of this slope is higher among the lower mass star-forming galaxies and those above the main sequence compared to quenched galaxies, due to lack of an evolved bulge. Our findings agree well with an inside-out quenching of star formation. We find that the knee of the Schechter fits (M*) for galaxies below the main sequence occurs at lower stellar mass surface densities compared to star-forming galaxies, which hints at how far quenching has proceeded outward.

Keywords: Galaxy bulges, Galaxy structure, Astrostatistics, Star formation, Galaxy evolution, Galaxy quenching, Galaxies, Dynamical evolution
Coronal-jet-producing Minifilament Eruptions as a Possible Source of Parker Solar Probe Switchbacks. The Parker Solar Probe (PSP) has observed copious rapid magnetic field direction changes in the near-Sun solar wind. These features have been called "switchbacks," and their origin is a mystery. But their widespread nature suggests that they may be generated by a frequently occurring process in the Sun's atmosphere. We examine the possibility that the switchbacks originate from coronal jets. Recent work suggests that many coronal jets result when photospheric magnetic flux cancels, and forms a small-scale "minifilament" flux rope that erupts and reconnects with coronal field. We argue that the reconnected erupting-minifilament flux rope can manifest as an outward propagating Alfvénic fluctuation that steepens into an increasingly compact disturbance as it moves through the solar wind. Using previous observed properties of coronal jets that connect to coronagraph-observed white-light jets (a.k.a. "narrow CMEs"), along with typical solar wind speed values, we expect the coronal-jet-produced disturbances to traverse near-perihelion PSP in ≲25 minutes, with a velocity of ∼400 km s-1. To consider further the plausibility of this idea, we show that a previously studied series of equatorial latitude coronal jets, originating from the periphery of an active region, generate white-light jets in the outer corona (seen in STEREO/COR2 coronagraph images; 2.5-15 R⊙), and into the inner heliosphere (seen in Solar-Terrestrial Relations Observatory (STEREO)/Hi1 heliospheric imager images; 15-84 R⊙). Thus it is tenable that disturbances put onto open coronal magnetic field lines by coronal-jet-producing erupting-minifilament flux ropes can propagate out to PSP space and appear as switchbacks.

Keywords: Solar magnetic fields, Solar wind, Solar filament eruptions, Solar magnetic reconnection
Optical Observations Reveal Strong Evidence for High-energy Neutrino Progenitor. We present the earliest astronomical observation of a high-energy neutrino error box of which the variability was discovered after high-energy-neutrino detection. The one robotic telescope of the MASTER global international networks automatically imaged the error box of the very high-energy-neutrino event IceCube-170922A. Observations were carried out in minutes after the IceCube-170922A neutrino event was detected by the IceCube observatory at the South Pole. MASTER found the blazar TXS 0506+056 to be in the off-state after one minute and then switched to the on-state no later than two hours after the event. The effect is observed at a 50σ significance level. We also present own a unique 16 yr light curve of blazar TXS 0506+056 (518 data set).

Keywords: Black holes, High energy astrophysics, Ultra-high-energy cosmic radiation, Blazars, Neutrino astronomy, Active galactic nuclei, Automatic patrol telescopes, Automated telescopes, Particle astrophysics
An Unambiguous Separation of Gamma-Ray Bursts into Two Classes from Prompt Emission Alone. The duration of a gamma-ray burst (GRB) is a key indicator of its physical origin, with long bursts perhaps associated with the collapse of massive stars and short bursts with mergers of neutron stars. However, there is substantial overlap in the properties of both short and long GRBs and neither duration nor any other parameter so far considered completely separates the two groups. Here we unambiguously classify every GRB using a machine-learning dimensionality reduction algorithm, t-distributed stochastic neighborhood embedding, providing a catalog separating all Swift GRBs into two groups. Although the classification takes place only using prompt emission light curves, every burst with an associated supernova is found in the longer group and bursts with kilonovae in the short, suggesting along with the duration distributions that these two groups are truly long and short GRBs. Two bursts with a clear absence of a supernova belong to the longer class, indicating that these might have been direct-collapse black holes, a proposed phenomenon that may occur in the deaths of more massive stars.

Keywords: Gamma-ray bursts, Light curve classification , High energy astrophysics, Astronomy data analysis, Astronomy data visualization, Supernovae
VLA-ALMA Spectroscopic Survey in the Hubble Ultra Deep Field (VLASPECS): Total Cold Gas Masses and CO Line Ratios for z = 2-3 Main-sequence Galaxies. Using the NSF's Karl G. Jansky Very Large Array (VLA), we report six detections of CO(J = 1 → 0) emission and one upper limit in z = 2-3 galaxies originally detected in higher-J CO emission in the Atacama Large Millimeter/submillimeter Array Spectroscopic Survey in the Hubble Ultra Deep Field (ASPECS). From the CO(J = 1 → 0) line strengths, we measure total cold molecular gas masses of Mgas = (2.4-11.6) × 1010 (αCO/3.6)M⊙. We also measure a median CO(J = 3 → 2) to CO(J = 1 → 0) line brightness temperature ratio of r31 = 0.84 ± 0.26, and a CO(J = 7 → 6) to CO(J = 1 → 0) ratio range of r71 &lt; 0.05 to r71 = 0.17. These results suggest that CO(J = 3 → 2) selected galaxies may have a higher CO line excitation on average than CO(J = 1 → 0) selected galaxies, based on the limited, currently available samples from the ASPECS and VLA CO Luminosity Density at High Redshift (COLDz) surveys. This implies that previous estimates of the cosmic density of cold gas in galaxies based on CO(J = 3 → 2) measurements should be revised down by a factor of ≃2 on average based on assumptions regarding CO excitation alone. This correction further improves the agreement between the best currently existing constraints on the cold gas density evolution across cosmic history from line scan surveys, and the implied characteristic gas depletion times.

Keywords: Observational astronomy, Molecular gas, Galaxy formation, Star formation, Galaxy evolution, Radio observatories, Redshift surveys