adsabs/SciX_UAT_keywords huggingface dataset:
Clustering of Local Group Distances: Publication Bias or Correlated Measurements? VI. Extending to Virgo Cluster Distances

We have established an internally consistent Local Group distance framework, using the Galactic Center, the Large Magellanic Cloud, and Messier 31 (M31) as important stepping stones. At greater distances, few distance benchmarks are available. As a consequence, M87 and/or Virgo cluster distances are often invoked as the next rung on the ladder to more distant objects such as the Fornax and Coma clusters. Therefore, we extensively mined the published literature for independently derived distance estimates to either M87 or the center of the Virgo cluster. Based on our newly compiled, comprehensive database of 213 such distances, published between 1929 and 2017 July, we recommend an outward extension to our distance framework, (m-M{)}0{{M}87}=31.03+/- 0.14 mag (D = 16.07 ± 1.03 Mpc; where the uncertainty represents the Gaussian σ of the distribution), based on a subset of recent (post-1990) M87/Virgo cluster distance measurements. The most stable distance tracers employed here were derived from analysis of both primary and secondary distance indicators. Among the former, we preferentially rely on Cepheid period-luminosity relations and red-giant-branch terminal magnitudes; our preferred secondary distance tracers are surface brightness fluctuations. Our updated distance modulus to M87 implies a slightly reduced black hole mass of (5.9 ± 0.6) × 109 M ⊙ with respect to that determined by the Event Horizon Telescope collaboration.

Keywords: astronomical reference materials; astronomy databases; distance measure; galaxy distances; virgo cluster
Gas Sources from the Coma and Nucleus of Comet 46P/Wirtanen Observed Using ALMA

Gas-phase molecules in cometary atmospheres (comae) originate primarily from (1) outgassing by the nucleus, (2) sublimation of icy grains in the near-nucleus coma, and (3) coma (photo)chemical processes. However, the majority of cometary gases observed at radio wavelengths have yet to be mapped, so their production/release mechanisms remain uncertain. Here we present observations of six molecular species toward comet 46P/Wirtanen, obtained using the Atacama Large Millimeter/submillimeter Array during the comet's unusually close (~0.1 au) approach to Earth in 2018 December. Interferometric maps of HCN, CH3OH, CH3CN, H2CO, CS, and HNC were obtained at an unprecedented sky-projected spatial resolution of up to 25 km, enabling the nucleus and coma sources of these molecules to be accurately quantified. The HCN, CH3OH, and CH3CN spatial distributions are consistent with production by direct outgassing from (or very close to) the nucleus, with a significant proportion of the observed CH3OH originating from sublimation of icy grains in the near-nucleus coma (at a scale length L p = 36 ± 7 km). On the other hand, H2CO, CS, and HNC originate primarily from distributed coma sources (with L p values in the range 550-16,000 km), the identities of which remain to be established. The HCN, CH3OH, and HNC abundances in 46P are consistent with the average values previously observed in comets, whereas the H2CO, CH3CN, and CS abundances are relatively low.

Keywords: short period comets; comet volatiles; interstellar molecules; radio interferometry; millimeter-wave spectroscopy; molecular spectroscopy; high resolution spectroscopy; radiative transfer
First Results from SMAUG: The Need for Preventative Stellar Feedback and Improved Baryon Cycling in Semianalytic Models of Galaxy Formation

Semianalytic models (SAMs) are a promising means of tracking the physical processes associated with galaxy formation, but many of their approximations have not been rigorously tested. As part of the Simulating Multiscale Astrophysics to Understand Galaxies project, we compare predictions from the FIRE-2 hydrodynamical "zoom-in" simulations to those from the Santa Cruz SAM run on the same halo merger trees, with an emphasis on the global mass flow cycle. Our study includes 13 halos spanning low-mass dwarfs (Mvir ∼ 1010M⊙ at z = 0), intermediate-mass dwarfs (Mvir ∼ 1011M⊙), and Milky Way-mass galaxies (Mvir ∼ 1012M⊙). The SAM and FIRE-2 predictions agree relatively well with each other in terms of stellar and interstellar medium mass but differ dramatically on circumgalactic medium mass (the SAM is lower than FIRE-2 by ∼3 orders of magnitude for dwarfs). Strikingly, the SAM predicts higher gas accretion rates for dwarfs compared to FIRE-2 by factors of ∼10-100, and this is compensated for with higher mass outflow rates in the SAM. We argue that the most severe model discrepancies are caused by the lack of preventative stellar feedback and the assumptions for halo gas cooling and recycling in the SAM. As a first step toward resolving these model tensions, we present a simple yet promising new preventative stellar feedback model in which the energy carried by supernova-driven winds is allowed to heat some fraction of gas outside of halos to at least the virial temperature such that accretion is suppressed.

Keywords: galaxy formation; galactic winds; galaxy evolution; circumgalactic medium; dwarf galaxies; galaxy dark matter halos; hydrodynamical simulations; analytical mathematics; star formation
Golden Galactic Binaries for LISA: Mass-transferring White Dwarf Black Hole Binaries

We study the evolution and gravitational wave emission of white dwarf-black hole accreting binaries with a semianalytical model. These systems will evolve across the mHz gravitational wave frequency band and potentially be detected by the Laser Interferometer Space Antenna (LISA). We identify new universal relations for this class of binaries, which relate the component masses to the gravitational wave frequency and its first derivative. Combined with the high precision measurements possible with LISA, these relations could allow us to infer the component masses and the luminosity distance of the source. LISA has therefore the potential to detect and characterize a virtually unexplored binary population.

Keywords: gravitational waves; accretion; compact binary stars; white dwarf stars; astrophysical black holes
SPCANet: Stellar Parameters and Chemical Abundances Network for LAMOST-II Medium Resolution Survey

The fundamental stellar atmospheric parameters (Teff and log g) and 13 chemical abundances are derived for medium-resolution spectroscopy from Large Sky Area Multi-Object Fiber Spectroscopic Telescope (LAMOST) Medium Resolution Survey (MRS) data sets with a deep-learning method. The neural networks we designed, named SPCANet, precisely map LAMOST MRS spectra to stellar parameters and chemical abundances. The stellar labels derived by SPCANet have precisions of 119 K for Teff and 0.17 dex for log g. The abundance precision of 11 elements including [C/H], [N/H], [O/H], [Mg/H], [Al/H], [Si/H], [S/H], [Ca/H], [Ti/H], [Cr/H], [Fe/H], and [Ni/H] are 0.06 ∼ 0.12 dex, while that of [Cu/H] is 0.19 dex. These precisions can be reached even for spectra with signal-to-noise ratios as low as 10. The results of SPCANet are consistent with those from other surveys such as APOGEE, GALAH, and RAVE, and are also validated with the previous literature values including clusters and field stars. The catalog of the estimated parameters is available at doi:10.12149/101012.

Keywords: stellar atmospheres; spectroscopy
Starburst-induced Gas–Star Kinematic Misalignment

A kinematic misalignment of the stellar and gas components is a phenomenon observed in a significant fraction of galaxies. However, the underlying physical mechanisms are not well understood. A commonly proposed scenario for the formation of a misaligned component requires any preexisting gas disk to be removed, via flybys or ejective feedback from an active galactic nucleus. In this Letter, we study the evolution of a Milky Way mass galaxy in the FIREbox cosmological volume that displays a thin, counterrotating gas disk with respect to its stellar component at low redshift. In contrast to scenarios involving gas ejection, we find that preexisting gas is mainly removed via the conversion into stars in a central starburst, triggered by a merging satellite galaxy. The newly accreted, counterrotating gas eventually settles into a kinematically misaligned disk. About 4% (8 out of 182) of FIREbox galaxies with stellar masses larger than 5 × 109 M ⊙ at z = 0 exhibit gas–star kinematic misalignment. In all cases, we identify central starburst-driven depletion as the main reason for the removal of the preexisting corotating gas component, with no need for feedback from, e.g., a central active black hole. However, during the starburst, the gas is funneled toward the central regions, likely enhancing black hole activity. By comparing the fraction of misaligned discs between FIREbox and other simulations and observations, we conclude that this channel might have a non-negligible role in inducing kinematic misalignment in galaxies.

Keywords: hydrodynamical simulations; galaxy evolution; galaxy structure; starburst galaxies
Small-scale Induced Large-scale Transitions in Solar Wind Magnetic Field

We investigate the role of small-scale dynamics in inducing large-scale transitions in the solar wind magnetic field by means of dynamical system metrics based on instantaneous fractal dimensions. By looking at the corresponding multiscale features, we observe a break in the average attractor dimension occurring at the crossover between the inertial and the kinetic/dissipative regime. Our analysis suggests that large-scale transitions are induced by small-scale dynamics through an inverse cascade mechanism driven by local correlations, while electron contributions (if any) are hidden by instrumental noise.

Keywords: solar wind; magnetohydrodynamics; space plasmas; interplanetary turbulence
A Comprehensive Catalog of Dark Matter Halo Models for SPARC Galaxies

We present rotation curve fits to 175 late-type galaxies from the Spitzer Photometry and Accurate Rotation Curves database using seven dark matter (DM) halo profiles: pseudo-isothermal, Burkert, Navarro-Frenk-White (NFW), Einasto, Di Cintio et al. (2014, hereafter DC14), cored-NFW, and a new semi-empirical profile named Lucky13. We marginalize over the stellar mass-to-light ratio, galaxy distance, disk inclination, halo concentration, and halo mass (and an additional shape parameter for Einasto) using a Markov Chain Monte Carlo method. We find that cored halo models, such as the DC14 and Burkert profiles, generally provide better fits to rotation curves than the cuspy NFW profile. The stellar mass-halo mass relation from abundance matching is recovered by all halo profiles once imposed as a Bayesian prior, whereas the halo mass-concentration relation is not reproduced in detail by any halo model. We provide an extensive set of figures as well as best-fit parameters in machine-readable tables to facilitate model comparison and the exploration of DM halo properties.

Keywords: galaxy dark matter halos; galaxy dynamics; galaxy formation; galaxy evolution; galaxy rotation curves; galaxy kinematics; dark matter distribution; cold dark matter; spiral galaxies; dwarf galaxies; late-type galaxies
Ejecta Formation, Early Collisional Processes, and Dynamical Evolution after the DART Impact on Dimorphos

NASA's DART spacecraft is planned to reach and impact asteroid Dimorphos, the small moon of binary asteroid (65803) Didymos, at a velocity of 6 km s-1 in late 2022 September. DART will be the first mission to test the "kinetic impactor" technique, aimed at deflecting the orbital path of a potentially hazardous asteroid. The success and effectiveness of this technique resides in the efficiency of momentum exchange between the spacecraft and the impacted target. This depends on many factors, including the cratering process, the formation of ejecta, and their fate, as they remain in the system or escape from it, carrying momentum away. Here we provide an overview of the cratering process, including ejecta formation and their subsequent dynamical evolution. We use different methodologies to model the physics of the problem, including smoothed particle hydrodynamics to model the cratering and ejecta formation process after the hypervelocity impact, N-body granular simulations to model early collisional processes between ejecta fragments right after cratering, and high-fidelity planetary propagation to model the dynamical evolution of ejecta during their purely ballistic phase. We highlight the key features of each phase and their role in defining the dynamical fate of ejecta. We investigate the effect of surface cohesion in the impacted target and identify the qualitative behavior of ejecta particles as a function of the key parameters of the problem. We provide quantitative estimates for the specific case study related to the DART-Dimorphos scenario and a selected range of target properties.

Keywords: asteroid dynamics; impact phenomena; planetary science; astrodynamics; n-body problem; three-body problem; ejecta
Change in the Radio Structure and Position of the Quasar CTA 21

Astrometric positions of radio-emitting active galactic nuclei (AGNs) can be determined with sub-milliarcsec accuracy using very long baseline interferometry (VLBI). The usually small apparent proper motion of distant extragalactic targets allow us to realize the fundamental celestial reference frame with VLBI observations. However, long-term astrometric monitoring may reveal extreme changes in some AGN positions. We present the case of CTA 21 whose position gradually shifted by ∼0"04 over two decades. By comparing archival VLBI images from 1996 and 2018, we show that its radio structure changed substantially, likely causing the apparent positional shift.

Keywords: radio astrometry; active galactic nuclei; extragalactic radio sources; very long baseline interferometry
Source-dependent Properties of Two Slow Solar Wind States

Two states of the slow solar wind are identified from in situ measurements by the Parker Solar Probe (PSP) inside 50 solar radii from the Sun. At such distances the wind measured by PSP has not yet undergone significant transformation related to the expansion and propagation of the wind. We focus in this study on the properties of the quiet solar wind with no magnetic switchbacks. The two states differ by their plasma beta, flux, and magnetic pressure. PSP's magnetic connectivity established with potential field source surface reconstructions, tested against extreme ultraviolet and white-light imaging, reveals the two states correspond to a transition from a streamer to an equatorial coronal hole. The expansion factors of magnetic field lines in the streamer are 20 times greater than those rooted near the center of the coronal hole. The very different expansion rates of the magnetic field result in different magnetic pressures measured by PSP in the two plasma states. Solar wind simulations run along these differing flux tubes reproduce the slower and denser wind measured in the streamer and the more tenuous wind measured in the coronal hole. Plasma heating is more intense at the base of the streamer field lines rooted near the boundary of the equatorial hole than those rooted closer to the center of the hole. This results in a higher wind flux driven inside the streamer than deeper inside the equatorial hole.

Keywords: slow solar wind; solar wind; solar coronal holes; solar coronal streamers
Explicit Symplectic Methods in Black Hole Spacetimes

Many Hamiltonian problems in the solar system are separable into two analytically solvable parts, and thus serve as a great chance to develop and apply explicit symplectic integrators based on operator splitting and composing. However, such constructions are not in general available for curved spacetimes in general relativity and modified theories of gravity because these curved spacetimes correspond to nonseparable Hamiltonians without the two-part splits. Recently, several black hole spacetimes such as the Schwarzschild black hole were found to allow for the construction of explicit symplectic integrators, since their corresponding Hamiltonians are separable into more than two explicitly integrable pieces. Although some other curved spacetimes including the Kerr black hole do not have such multipart splits, their corresponding appropriate time-transformation Hamiltonians do. In fact, the key problem in obtaining symplectic analytically integrable decomposition algorithms is how to split these Hamiltonians or time-transformation Hamiltonians. Considering this idea, we develop explicit symplectic schemes in curved spacetimes. We introduce a class of spacetimes whose Hamiltonians are directly split into several explicitly integrable terms. For example, the Hamiltonian of a rotating black ring has a 13-part split. We also present two sets of spacetimes whose appropriate time-transformation Hamiltonians have the desirable splits. For instance, an eight-part split exists in a time-transformed Hamiltonian of a Kerr-Newman solution with a disformal parameter. In this way, the proposed symplectic splitting methods can be used widely for long-term integrations of orbits in most curved spacetimes we know of.

Keywords: achondrites; computational methods; computational astronomy; celestial mechanics
A Theoretical Study of Infrared Spectra of Highly Positively Charged C60 Fullerenes and Their Relevance to Observed UIE Features

By applying first principles quantum chemical calculations, we present a complete catalog of the theoretically expected mid-infrared signatures of cationic forms of fullerene with the general formula of ${{\rm{C}}}_{60}^{q+}$ (q = 1-26). The structural stability and bonding of these exotic species have been reported by us elsewhere. It is found that not only can some of these cations contribute significantly to the flux of the 17.4 and 18.9 μm bands of fullerene that are observed in some planetary nebulae but they also show strong bands that match the position of key astronomical unidentified infrared emission at 11.21, 16.40 and 20-21 μm, which makes them key species for identification. It is also found that the IR signatures of the group of these cations with q = 1-6 are well separated from the 6.2 μm band that is associated with free/isolated aromatic hydrocarbon molecules. This is particularly important in the discrimination and exploration of the coexistence of complex hydrocarbon organics and fullerenes in astronomical sources. To provide insight into the effect of ionization on the IR spectrum of fullerene, particularly at the long-wavelength range, the quantitative analysis of the origin of key bands of these cations is presented. Finally, the potential target(s) among these species, specifically aromatic ${{\rm{C}}}_{60}^{10+}$ , are discussed for further astrochemical observations.

Keywords: astrochemistry; theoretical techniques; planetary nebulae; infrared astronomy; interstellar molecules
Realistic Detection and Early Warning of Binary Neutron Stars with Decihertz Gravitational-wave Observatories

We investigated the detection rates and early-warning parameters of binary neutron star (BNS) populations with decihertz gravitational-wave observatories in a realistic detecting strategy. Assuming the operation time of B-DECIGO is 4 yr, we classified the detectable BNSs based on parameter precision into three categories: (a) sources that merge within 1 yr, which could be localized with an uncertainty of ΔΩ ~ 100 deg2; (b) sources that merge in 1-4 yr, which take up three-quarters of the total events and yield the most precise angular resolution with ΔΩ ~ 10-2 deg2 and time-of-merger accuracy with Δt c ~ 10-1 s; and (c) sources that do not merge during the 4 yr mission window, which enable possible early warnings, with ΔΩ ~ 10-1 deg2 and Δt c ~ 100 s. Furthermore, we compared the pros and cons of B-DECIGO with the third-generation ground-based detectors, and explored the prospects of detections using three other decihertz observatories and four BNS population models. In realistic observing scenarios, we found that decihertz detectors could even provide early-warning alerts to a source decades before its merger while their localizations are still as accurate as ground-based facilities. Finally we found a decrease of events when considering the confusion noise, but this could be partially solved by a proper noise subtraction.

Keywords: gravitational wave astronomy; neutron stars; gravitational wave detectors
On the Utility of Transmission Color Analysis I: Differentiating Super-Earths and Sub-Neptunes

The majority of exoplanets found to date have been discovered via the transit method, and transmission spectroscopy represents the primary method of studying these distant worlds. Currently, in-depth atmospheric characterization of transiting exoplanets entails the use of spectrographs on large telescopes, requiring significant observing time to study each planet. Previous studies have demonstrated trends for solar system worlds using color-color photometry of reflectance spectra, as well as trends within transmission spectra for hot Jupiters. Building on these concepts, we have investigated the use of transmission color photometric analysis for efficient, coarse categorization of exoplanets and for assessing the nature of these worlds, with a focus on resolving the bulk composition degeneracy to aid in discriminating super-Earths and sub-Neptunes. We present our methodology and first results, including spectrum models, model comparison frameworks, and wave band selection criteria. We present our results for different transmission "color" metrics, filter selection methods, and numbers of filters. Assuming noise-free spectra of isothermal atmospheres in chemical equilibrium, with our pipeline, we are able to constrain atmospheric mean molecular weight in order to distinguish between super-Earth and sub-Neptune atmospheres with >90% overall accuracy using specific low-resolution filter combinations, . We also found that increasing the number of filters does not substantially impact this performance. This method could allow for broad characterization of large numbers of planets much more efficiently than current methods permit, enabling population- and system-level studies. Additionally, data collected via this method could inform follow-up observing time by large telescopes for more detailed studies of worlds of interest.

Keywords: exoplanet atmospheres; transmission spectroscopy; super earths; mini neptunes; transit photometry; atmospheric composition
Broadband Variability and Correlation Study of 3C 279 during Flares of 2017-2018

A multiwavelength temporal and spectral analysis of flares of 3C 279 during 2017 November-2018 July are presented in this work. Three bright gamma-ray flares were observed simultaneously in X-ray and optical/UV along with a prolonged quiescent state. A "harder-when-brighter" trend is observed in both gamma-rays and X-rays during the flaring period. The gamma-ray light curve for all the flares is binned in one day time bins and a day-scale variability is observed. Variability time constrains the size and location of the emission region to 2.1 × 1016 cm and 4.4 × 1017 cm, respectively. The fractional variability reveals that the source is more than 100% variable in gamma-rays and it decreases toward the lower energy. A cross-correlation study of the emission from different wavebands is done using the discrete correlations function method, which shows a strong correlation between them without any time lags. The zero time lag between different wavebands suggests their cospatial origin. This is the first time 3C 279 has shown a strong correlation between gamma-ray and X-ray emission with zero time lag. A single-zone emission model was adopted to model the multiwavelength spectral energy distributions by using the publicly available code GAMERA. The study reveals that a higher jet power in electrons is required to explain the gamma-ray flux during the flaring state, as much as 10 times that required for the quiescent state. However, more jet power in the magnetic field has been observed during the quiescent state compared to the flaring state.

Keywords: active galaxies; quasars; jets; gamma-rays; blazars; galactic and extragalactic astronomy