adsabs/SciX_UAT_keywords huggingface dataset:
Dust Polarization of Prestellar and Protostellar Sources in OMC-3

We present the Atacama Large Millimeter/submillimeter Array observations of linearly polarized 1.1 mm continuum emission at ∼0.″14 (55 au) resolution and CO (J = 2‑1) emission at ∼1.″5 (590 au) resolution toward one prestellar (MMS 4), four Class 0 (MMS 1, MMS 3, MMS 5, and MMS 6), one Class I (MMS 7), and one flat-spectrum (MMS 2) sources in the Orion Molecular Cloud 3 region. The dust disk-like structures and clear CO outflows are detected toward all sources except for MMS 4. The diameters of these disk-like structures, ranging from 16 to 97 au, are estimated based on the deconvolved full width half maximum (FWHM) values obtained from the multi-Gaussian fitting. Polarized emissions are detected toward MMS 2, MMS 5, MMS 6, and MMS 7, while no polarized emission is detected toward MMS 1, MMS 3, and MMS 4. MMS 2, MMS 5, and MMS 7 show organized polarization vectors aligned with the minor axes of the disk-like structures, with mean polarization fractions ranging from 0.6% to 1.2%. The strongest millimeter source, MMS 6, exhibits complex polarization orientations and a remarkably high polarization fraction of ∼10% around the Stokes I peak, and 15%–20% on the arm-like structure, as reported by Takahashi et al. (2019). The origins of the polarized emission, such as self-scattering and dust alignment due to the magnetic field or radiative torque, are discussed for individual sources. Some disk-like sources exhibit a polarized intensity peak shift toward the nearside of the disk, which supports that the polarized emission originates from self-scattering.

Keywords: polarimetry; dust continuum emission; young stellar objects
A Self-consistent, Time-dependent Treatment of Dynamical Friction: New Insights Regarding Core Stalling and Dynamical Buoyancy

Dynamical friction is typically regarded as a secular process, in which the subject ("perturber") evolves very slowly (secular approximation) and has been introduced to the host over a long time (adiabatic approximation). These assumptions imply that dynamical friction arises from the LBK torque with nonzero contribution only from purely resonant orbits. However, dynamical friction is only of astrophysical interest if its timescale is shorter than the age of the universe. In this paper we therefore relax the adiabatic and secular approximations. We first derive a generalized LBK torque, which reduces to the LBK torque in the adiabatic limit, and show that it gives rise to transient oscillations due to nonresonant orbits that slowly damp out, giving way to the LBK torque. This is analogous to how a forced, damped oscillator undergoes transients before settling to a steady state, except that here the damping is due to phase mixing rather than dissipation. Next, we present a self-consistent treatment that properly accounts for time dependence of the perturber potential and circular frequency (memory effect), which we use to examine orbital decay in a cored galaxy. We find that the memory effect results in a phase of accelerated, super-Chandrasekhar friction before the perturber stalls at a critical radius, Rcrit, in the core (core stalling). Inside Rcrit the torque flips sign, giving rise to dynamical buoyancy, which counteracts friction and causes the perturber to stall. This phenomenology is consistent with N-body simulations, but has thus far eluded proper explanation.

Keywords: dynamical friction; orbital resonances; gravitational interaction; stellar dynamics; galaxy dark matter halos; galaxy nuclei
GASP XXVII: Gas-phase Metallicity Scaling Relations in Disk Galaxies with and without Ram Pressure Stripping

Exploiting the data from the GAs Stripping Phenomena in galaxies with MUSE (GASP) survey, we study the gas-phase metallicity scaling relations of a sample of 29 cluster galaxies undergoing ram pressure stripping and of a reference sample of (16 cluster and 16 field) galaxies with no significant signs of gas disturbance. We adopt the PYQZ code to infer the mean gas metallicity at the effective radius and achieve a well-defined mass-metallicity relation (MZR) in the stellar mass range ${10}^{9.25}\leqslant {M}_{\star }\leqslant {10}^{11.5}\,{M}_{\odot }$ with a scatter of 0.12 dex. At any given mass, reference cluster and stripping galaxies have similar metallicities, while the field galaxies with M⋆ < 1010.25 M⊙ show on average lower gas metallicity than galaxies in clusters. Our results indicate that at the effective radius, the chemical properties of the stripping galaxies are independent of the ram pressure stripping mechanism. Nonetheless, at the lowest masses, we detect four stripping galaxies well above the common MZR that suggest a more complex scenario. Overall, we find signs of an anticorrelation between the metallicity and both the star formation rate and the galaxy size, in agreement with previous studies. No significant trends are instead found with the halo mass, clustercentric distance, and local galaxy density in clusters. In conclusion, we advise a more detailed analysis of the spatially resolved gas metallicity maps of the galaxies, able to highlight effects of gas redistribution inside the disk due to ram pressure stripping.

Keywords: galaxies; field galaxies; galaxy clusters; metallicity; galaxy chemical evolution
SDSS-IV MaNGA: The Radial Profile of Enhanced Star Formation in Close Galaxy Pairs

We compare the radial profiles of the specific star formation rate (sSFR) in a sample of 169 star-forming galaxies in close pairs with those of mass-matched control galaxies in the SDSS-IV MaNGA survey. We find that the sSFR is centrally enhanced (within one effective radius) in interacting galaxies by ∼0.3 dex and that there is a weak sSFR suppression in the outskirts of the galaxies of ∼0.1 dex. We stack the difference profiles for galaxies in five stellar-mass bins in the range log(M/M⊙) = 9.0-11.5 and find that the sSFR enhancement has no dependence on the stellar mass. The same result is obtained when comparison galaxies are matched to each paired galaxy in both stellar mass and redshift. In addition, we find that the sSFR enhancement is elevated in pairs with nearly equal masses and closer projected separations, in agreement with previous work based on single-fiber spectroscopy. We also find that the sSFR offsets in the outskirts of the paired galaxies are dependent on whether the galaxy is the more-massive or less-massive companion in the pair. The more-massive companion experiences zero to a positive sSFR enhancement, while the less-massive companion experiences sSFR suppression in their outskirts. Our results illustrate the complex tidal effects on star formation in closely paired galaxies.

Keywords: star formation; galaxy nuclei; galaxy interactions; galaxy mergers; galaxy pairs
MOA-2007-BLG-400 A Super-Jupiter-mass Planet Orbiting a Galactic Bulge K-dwarf Revealed by Keck Adaptive Optics Imaging

We present Keck/NIRC2 adaptive optics imaging of planetary microlensing event MOA-2007-BLG-400 that resolves the lens star system from the source. We find that the MOA-2007-BLG-400L planetary system consists of a 1.71 ± 0.27MJup planet orbiting a 0.69 ± 0.04M⊙ K-dwarf host star at a distance of 6.89 ± 0.77 kpc from the Sun. So, this planetary system probably resides in the Galactic bulge. The planet-host star projected separation is only weakly constrained due to the close-wide light-curve degeneracy; the 2σ projected separation ranges are 0.6-1.0 au and 4.7-7.7 au for close and wide solutions, respectively. This host mass is at the top end of the range of masses predicted by a standard Bayesian analysis. Our Keck follow-up program has now measured lens-source separations for six planetary microlensing events, and five of these six events have host star masses above the median prediction under the assumption that assumes that all stars have an equal chance of hosting planets detectable by microlensing. This suggests that more massive stars may be more likely to host planets of a fixed mass ratio that orbit near or beyond the snow line. These results also indicate the importance of host star mass measurements for exoplanets found by microlensing. The microlensing survey imaging data from NASA's Nancy Grace Roman Space Telescope (formerly WFIRST) mission will be doing mass measurements like this for a huge number of planetary events.

Keywords: exoplanets; high-resolution microlensing event imaging; gravitational microlensing
An ALMA Search for Substructure and Fragmentation in Starless Cores in Orion B North

We present Atacama Large Millimeter/submillimeter Array (ALMA) Cycle 3 observations of 73 starless and protostellar cores in the Orion B North molecular cloud. We detect a total of 34 continuum sources at 106 GHz, and after comparisons with other data, four of these sources appear to be starless. Three of the four sources are located near groupings of protostellar sources, while one source is an isolated detection. We use synthetic observations of a simulation modeling a collapsing turbulent, magnetized core to compute the expected number of starless cores that should be detectable with our ALMA observations and find at least two (1.52) starless cores should be detectable (at 5σ), consistent with our data. We run a simple virial analysis of the cores to put the Orion B North observations into context with similar previous ALMA surveys of cores in Chamaeleon I and Ophiuchus. We conclude that the Chamaeleon I starless core population is characteristically less bounded than the other two populations, along with external pressure contributions dominating the binding energy of the cores. These differences may explain why the Chamaeleon I cores do not follow turbulent model predictions, while the Ophiuchus and Orion B North cores are consistent with the model.

Keywords: star formation; molecular clouds; collapsing clouds; star forming regions; radio interferometry; millimeter astronomy; submillimeter astronomy; dust continuum emission
Magnetic-field Induced Deformation in Hybrid Stars

The effects of strong magnetic fields on the deconfinement phase transition expected to take place in the interior of massive neutron stars are studied in detail for the first time. For hadronic matter, the very general density-dependent relativistic mean field model is employed, while the simple, but effective vector-enhanced bag model is used to study quark matter. Magnetic-field effects are incorporated into the matter equation of state and in the general-relativity solutions, which also satisfy Maxwell's equations. We find that for large values of magnetic dipole moment, the maximum mass, canonical mass radius, and dimensionless tidal deformability obtained for stars using spherically symmetric Tolman-Oppenheimer-Volkoff (TOV) equations and axisymmetric solutions attained through the LORENE library differ considerably. The deviations depend on the stiffness of the equation of state and on the star mass being analyzed. This points to the fact that, unlike what was assumed previously in the literature, magnetic field thresholds for the approximation of isotropic stars and the acceptable use of TOV equations depend on the matter composition and interactions.

Keywords: neutron stars; nuclear astrophysics; compact objects; magnetars; magnetic fields
Long-lived Eccentric Modes in Circumbinary Disks

Hydrodynamical simulations show that circumbinary disks become eccentric, even when the binary is circular. Here we demonstrate that, in steady state, the disk's eccentricity behaves as a long-lived free mode trapped by turning points that naturally arise from a continuously truncated density profile. Consequently, both the disk's precession rate and eccentricity profile may be calculated via the simple linear theory for perturbed pressure-supported disks. By formulating and solving the linear theory, we find that (i) surprisingly, the precession rate is roughly determined by the binary's quadrupole, even when the quadrupole is very weak relative to pressure; (ii) the eccentricity profile is largest near the inner edge of the disk and falls exponentially outward; and (iii) the results from linear theory indeed agree with what is found in simulations. Understanding the development of eccentric modes in circumbinary disks is a crucial first step for understanding the long-term (secular) exchange of eccentricity, angular momentum, and mass between the binary and the gas. Potential applications include the search for a characteristic kinematic signature in disks around candidate binaries and precession-induced modulation of accretion over long timescales.

Keywords: binary stars; stellar accretion disks; protoplanetary disks; supermassive black holes; theoretical techniques
How Do Supernovae Impact the Circumgalactic Medium? I. Large-scale Fountains around a Milky Way-like Galaxy

Feedback is indispensable in galaxy formation. However, lacking resolutions, cosmological simulations often use ad hoc feedback parameters. Conversely, small-box simulations, while they better resolve the feedback, cannot capture gas evolution beyond the simulation domain. We aim to bridge the gap by implementing small-box results of supernovae-driven outflows into dark matter halo-scale simulations and studying their impact on large scales. Galactic outflows are multiphase, but small-box simulations show that the hot phase (T ≈ 106-7 K) carries the majority of energy and metals. We implement hot outflows in idealized simulations of the Milky Way halo, and examine how they impact the circumgalactic medium. In this paper, we discuss the case when the star formation surface density is low and therefore the emerging hot outflows are gravitationally bound by the halo. We find that outflows form a large-scale, metal-enriched atmosphere with fountain motions. As hot gas accumulates, the inner atmosphere becomes "saturated." Cool gas condenses, with a rate balancing the injection of the hot outflows. This balance leads to a universal density profile of the hot atmosphere, independent of mass outflow rate. The atmosphere has a radially decreasing temperature, naturally producing the observed X-ray luminosity and column densities of O VI, O VII, and O VIII. The self-regulated atmosphere has a baryon and a metal mass of (0.5-1.2) × 1010 M⊙ and (0.6-1.4) × 108 M⊙, respectively, small compared to the "missing" baryons and metals from the halo. We conjecture that the missing materials reside at even larger radii, ejected by more powerful outflows in the past.

Keywords: galaxy formation; milky way formation; galaxy evolution; milky way evolution; circumgalactic medium; hydrodynamical simulations; galactic winds; disk galaxies; supernova remnants; chemical enrichment
Morphology of Solar Type II Bursts Caused by Shock Propagation through Turbulent and Inhomogeneous Coronal Plasma

Type II solar bursts are radio signatures of shock waves in the solar corona driven by solar flares or coronal mass ejections (CMEs). Therefore, these bursts present complex spectral morphologies in solar dynamic spectra. Here, we report meter-decameter radio observations of a type II burst on 2014 July 25 made with the Ukrainian radio telescopes UTR-2 (8.25-33 MHz) and GURT (8.25-78 MHz). The burst demonstrates fundamental and harmonic components, band splitting, a herringbone structure, and a spectral break. These specific spectral features, observed jointly in a single type II burst, are rarely detected. To contribute to our understanding of such puzzling type II events, we carried out a detailed analysis of the recorded type II dynamic spectrum. In particular, the herringbone pattern has been exploited to study electron density turbulence in the solar corona. We calculated the power spectral densities of the flux variations in selected herringbones. The spectral index is in the range of α = -1.69 to -2.00 with an average value of -1.897, which is slightly higher than the Kolmogorov spectral index of -5/3 for fully developed turbulence. We also recognized that the second type II burst consists of three drifting lanes. The lane onset times coincide with the spectral break in the first type II burst. We regard that the CME/shock passage through a streamer caused the spectral break and triggered the multilane type II radio emission. Thus, we support one of the proposed scenarios for type II burst occurrence as being the result of CME/shock-streamer interaction.

Keywords: solar coronal mass ejections; solar activity; solar telescopes; radio bursts; solar coronal streamers; solar coronal radio emission
Open Cluster IC 1369 and Its Vicinity: Multicolor Photometry and Gaia DR2 Astrometry

The open cluster IC 1369, located in Cygnus close to the galactic equator at the 89°6 longitude, and its vicinity are investigated by applying two-dimensional photometric classification of stars down to V = 19 mag measured in the Vilnius seven-color photometric system. Employing the Gaia DR2 coordinates, parallaxes, and proper motions, 143 cluster members are found having cluster membership probabilities ≥0.75. The hottest stars of the evolved main sequence are of spectral class B9. Distances to the cluster, determined by two methods based on the Gaia parallaxes, are 3280 and 3370 pc with an uncertainty of 400-500 pc. Employing the physical HR diagram with the coordinates $\mathrm{log}L/{L}_{\odot }$ versus $\mathrm{log}{T}_{\mathrm{eff}}$ and the Padova isochrones, the cluster age is found to be between 300 and 350 Myr. Among the cluster members we identified six red giants of spectral classes G5-G8 and luminosities II-III, 17 Am stars, one Ap star, and one B5 blue straggler. The extinction shows a steep rise up to ∼2.0 mag at 300-700 pc, caused by the extensions of the dust cloud LDN 970 and the Great Cygnus Rift, and up to ∼2.5 mag at the edge of the Perseus arm at 3.0 kpc. The extinction is almost constant between 0.9 and 2.5 kpc from the Sun. The average extinction of the cluster members is 2.54 mag. A systematic error of color excesses found in the Argonaut calculator results is discussed.

Keywords: open star clusters; stellar classification; hertzsprung russell diagram; interstellar dust extinction
The TeV Diffuse Cosmic Neutrino Spectrum and the Nature of Astrophysical Neutrino Sources

The diffuse flux of cosmic neutrinos has been measured by the IceCube Observatory from TeV to PeV energies. We show that an improved characterization of this flux at lower energies, TeV and sub-TeV, reveals important information on the nature of the astrophysical neutrino sources in a model-independent way. Most significantly, it could confirm the present indications that neutrinos originate in cosmic environments that are optically thick to GeV-TeV γ-rays. This conclusion will become inevitable if an uninterrupted or even steeper neutrino power law is observed in the TeV region. In such γ-ray-obscured sources, the γ-rays that inevitably accompany cosmic neutrinos will cascade down to MeV-GeV energies. The requirement that the cascaded γ-ray flux accompanying cosmic neutrinos should not exceed the observed diffuse γ-ray background puts constraints on the peak energy and density of the radiation fields in the sources. Our calculations inspired by the existing data suggest that a fraction of the observed diffuse MeV-GeV γ-ray background may be contributed by neutrino sources with intense radiation fields that obscure the high-energy γ-ray emission accompanying the neutrinos.

Keywords: neutrino astronomy; gamma-rays
Dynamical Unification of Tidal Disruption Events

The ~100 tidal disruption events (TDEs) observed so far exhibit a wide range of emission properties both at peak and over their lifetimes. Some TDEs radiate predominantly at X-ray energies, while others radiate chiefly at UV and optical wavelengths. While the peak luminosities across TDEs show distinct properties, the evolutionary behavior can also vary between TDEs with similar peak emission properties. In particular, for optical TDEs, while their UV and optical emissions decline somewhat following the fallback pattern, some events can greatly rebrighten in X-rays at late time. In this Letter, we conduct three-dimensional general relativistic radiation magnetohydrodynamics simulations of TDE accretion disks at varying accretion rates in the regime of super-Eddington accretion. We make use of Monte Carlo radiative transfer simulations to calculate the reprocessed spectra at various inclinations and at different evolutionary stages. We confirm the unified model proposed by Dai et al., which predicts that the observed emission largely depends on the viewing angle of the observer with respect to the disk orientation. Furthermore, we find that disks with higher accretion rates have elevated wind and disk densities, which increases the reprocessing of the high-energy radiation and thus generally augments the optical-to-X-ray flux ratio along a particular viewing angle. This implies that at later times, as the accretion level declines, we expect that more X-rays will leak out along intermediate viewing angles. Such dynamical model for TDEs can provide a natural explanation for the diversity in the emission properties observed in TDEs at peak and along their temporal evolution.

Keywords: accretion; astrophysical black holes; black hole physics; magnetohydrodynamics; radiative transfer; quasars
Technosignatures: Frameworks for Their Assessment

In view of the promising advancements in technosignature science, the question of what constitutes a robust technosignature is rendered crucial. In this paper, we first delineate a Bayesian framework for ascertaining the reliability of potential technosignatures by availing ourselves of recent cognate research in biosignatures. We demonstrate that ideal technosignatures must not only have low risk of stemming from false positives but also evince sufficiently high prior probability of existence. Given the inherent difficulties with estimating the latter, we highlight a few alternative metrics drawn from diagnostic testing such as the Youden index that bypass the requirement of explicitly calculating the prior. We apply the models (Bayesian or otherwise) to a select few technosignature candidates and show that artificial electromagnetic signals, chlorofluorocarbons, and artifacts perform well on this front. While these results may be along expected lines, we suggest that identifying and developing suitable approaches to further evaluate technosignature candidates is of considerable importance.

Keywords: astrobiology; search for extraterrestrial intelligence; technosignatures; bayesian statistics; bayes' theorem
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