adsabs/SciX_UAT_keywords huggingface dataset:
Cosmology with One Galaxy?

Galaxies can be characterized by many internal properties such as stellar mass, gas metallicity, and star formation rate. We quantify the amount of cosmological and astrophysical information that the internal properties of individual galaxies and their host dark matter halos contain. We train neural networks using hundreds of thousands of galaxies from 2000 state-of-the-art hydrodynamic simulations with different cosmologies and astrophysical models of the CAMELS project to perform likelihood-free inference on the value of the cosmological and astrophysical parameters. We find that knowing the internal properties of a single galaxy allows our models to infer the value of Ωm, at fixed Ωb, with a ~10% precision, while no constraint can be placed on σ 8. Our results hold for any type of galaxy, central or satellite, massive or dwarf, at all considered redshifts, z ≤ 3, and they incorporate uncertainties in astrophysics as modeled in CAMELS. However, our models are not robust to changes in subgrid physics due to the large intrinsic differences the two considered models imprint on galaxy properties. We find that the stellar mass, stellar metallicity, and maximum circular velocity are among the most important galaxy properties to determine the value of Ωm. We believe that our results can be explained by considering that changes in the value of Ωm, or potentially Ωb/Ωm, affect the dark matter content of galaxies, which leaves a signature in galaxy properties distinct from the one induced by galactic processes. Our results suggest that the low-dimensional manifold hosting galaxy properties provides a tight direct link between cosmology and astrophysics.

Keywords: galaxy formation; cosmological models; astrostatistics; hydrodynamical simulations
Revisiting the Vertical Distribution of H I Absorbing Clouds in the Solar Neighborhood

The vertical distribution of cold neutral hydrogen (H I) clouds is a constraint on models of the structure, dynamics, and hydrostatic balance of the interstellar medium. In 1978, Crovisier pioneered a method to infer the vertical distribution of H I absorbing clouds in the solar neighborhood. Using data from the Nançay 21 cm absorption survey, Crovisier determined the mean vertical displacement of cold H I clouds, <∣z∣>. We revisit that author's analysis and explore the consequences of truncating the H I absorption sample in Galactic latitude. For any nonzero latitude limit, we find that the quantity inferred by Crovisier is not the mean vertical displacement but rather a ratio involving higher moments of the vertical distribution. The resultant distribution scale heights are thus ∼1.5 to ∼3 times smaller than previously determined. In light of this discovery, we develop a Bayesian Monte Carlo Markov Chain method to infer the vertical distribution of H I absorbing clouds. We fit our model to the original Nançay data and find a vertical distribution moment ratio <∣z∣3>/<∣z∣2> = 97 ± 15 pc, which corresponds to a Gaussian scale height σ z = 61 ± 9 pc, an exponential scale height λ z = 32 ± 5 pc, and a rectangular half-width W z,1/2 = 129 ± 20 pc. Consistent with recent simulations, the vertical scale height of cold H I clouds appears to remain constant between the inner Galaxy and the Galactocentric distance of the solar neighborhood. Local fluctuations might explain the large-scale height observed at the same Galactocentric distance on the far side of the Galaxy.

Keywords: interstellar atomic gas; neutral hydrogen clouds; interstellar dynamics; cold neutral medium; radio astronomy; milky way disk
Blanco DECam Bulge Survey (BDBS). VI. Extinction Maps Toward Southern Galactic Bulge Globular Clusters

We present wide-field, high resolution maps of the color excess for 14 globular clusters toward the Southern Galactic bulge. The maps were derived using Gaia EDR3 astrometry and stellar photometry from the Blanco DECam Bulge Survey, which is a deep, wide-field ugrizY photometric survey of the southern Galactic bulge. Comparisons with WISE 12 μm images of thermal continuum emission demonstrate that the maps presented here trace interstellar extinction by dust down to 5″ scales. We use the reddening-corrected photometry of proper motion-selected cluster stars to build color-magnitude diagrams for the target globular clusters, which show residual broadening in excess of that expected from the photometric errors alone. This residual broadening is likely to be driven by star-to-star elemental abundance variations.

Keywords: globular star clusters; broad band photometry; interstellar dust extinction; red giant branch; galactic bulge
Soft X-Ray Observations of Quiescent Solar Active Regions Using the Novel Dual-zone Aperture X-Ray Solar Spectrometer

The Dual-zone Aperture X-ray Solar Spectrometer (DAXSS) was flown on 2018 June 18 on the NASA 36.336 sounding rocket flight and obtained the highest resolution to date for solar soft X-ray (SXR) spectra over a broad energy range. This observation was during a time with quiescent (nonflaring) small active regions on the solar disk and when the 10.7 cm radio flux (F10.7) was 75 solar flux units (1 sfu = 10-22 W m-2 Hz-1). The DAXSS instrument consists of a LASP-developed dual-zone aperture and a commercial X-ray spectrometer from Amptek that measures solar full-disk irradiance from 0.5 to 20 keV with a resolving power of 20 near 1 keV. This paper discusses the novel design of the spectrometer and the instrument characterization techniques. Additionally, the solar measurements obtained from the 2018 sounding rocket flight are analyzed using CHIANTI spectral models to fit the temperatures, emission measures, and relative elemental abundances of the solar corona plasma. The abundance of iron was found to be 35% higher than expected in the quiescent Sun's corona suggesting either that our spectral models require additional sophistication or that the underlying atomic database may require updates. Future long-term systematic observations of this spectral range are needed to provide further insight into the sources of coronal heating through modeling the changes of relative elemental abundances during developments of active regions and solar flaring events.

Keywords: solar x-ray emission; quiet sun; solar spectral irradiance; spectrometers; quiet solar corona; plasma physics
Stellar Atmospheric Parameters of ∼11,000 RR Lyrae Stars from LAMOST Spectra

Accurate determination of the stellar atmospheric parameters of RR Lyrae stars (RRLs) requires short individual exposures of the spectra to mitigate pulsation effects. We present improved template-matching methods to determine the stellar atmospheric parameters of RRLs from single-epoch spectra of the Large Sky Area Multi-Object Fiber Spectroscopic Telescope, also known as the Guoshoujing Telescope (LAMOST). We determine the radial velocities and stellar atmospheric parameters (effective temperature T eff, surface gravity $\mathrm{log}\,g$ , and metallicity [M/H]) of 10,486 and 1027 RRLs from 42,729 LAMOST low-resolution spectra (LRS) and 7064 LAMOST medium-resolution spectra (MRS), respectively. Our results are in good agreement with the parameters of other databases, where the external uncertainties of T eff, $\mathrm{log}\,g$ , and [M/H] for LRS/MRS are estimated to be 207/142 K, 0.21/0.16 dex, and 0.24/0.18 dex, respectively. We conclude with the variation characteristics of the radial velocities (RV) and stellar atmospheric parameters for RRLs during the pulsation phase. There is a significant difference of 28 ± 21 km s‑1 between the peak-to-peak amplitude (A ptp) of RV from the Hα line (RVHα ) and from metal lines (RVmetal) for RRab, whereas it is only 4 ± 17 km s‑1 for RRc. The A ptp of T eff is 930 ± 456 and 409 ± 375 K for RRab and RRc, respectively. The $\mathrm{log}\,g$ of RRab shows a mild variation of approximately 0.22 ± 0.42 dex near the phase of φ = 0.9, while that of RRc almost remains constant. The [M/H] of RRab and RRc show a minor variation of about 0.25 ± 0.50 and 0.28 ± 0.55 dex, respectively, near the phase of φ = 0.9. We expect that the determined stellar atmospheric parameters would shed new light on the study of stellar evolution and pulsation, the structure of the Milky Way, as well as other research fields.

Keywords: rr lyrae variable stars; spectroscopy; stellar atmospheres; stellar pulsations
GJ 229B: Solving the Puzzle of the First Known T Dwarf with the APOLLO Retrieval Code

GJ 229B was the first T dwarf to be discovered in 1995, and its spectrum has been more thoroughly observed than that of most other brown dwarfs. Yet a full spectroscopic analysis of its atmosphere has not been done with modern techniques. This spectrum has several peculiar features, and recent dynamical estimates of GJ 229B's mass and orbit have disagreed widely, both of which warrant closer investigation. With a separation of tens of astronomical units from its host star, GJ 229B falls near the border of the planet and stellar population formation regimes, so its atmosphere could provide clues to formation processes for intermediate objects of this type. In an effort to resolve these questions, we performed retrievals on published spectra of GJ 229B over a wide range of wavelengths (0.5-5.1 μm) using the open-source APOLLO code. Based on these retrievals, we present a more precise mass estimate of 41.6 ± 3.3 M J and an effective temperature estimate of ${869}_{-7}^{+5}$ K, which are more consistent with evolutionary models for brown dwarfs and suggest an older age for the system of >1.0 Gyr. We also present retrieved molecular abundances for the atmosphere, including replicating the previously observed high CO abundance, and discuss their implications for the formation and evolution of this object. This retrieval effort will give us insight into how to study other brown dwarfs and directly imaged planets, including those observed with JWST and other next-generation telescopes.

Keywords: t dwarfs; exoplanet atmospheres; spectroscopy; substellar companion stars
Incorporating Inner Magnetosphere Current-driven Electron Acceleration in Numerical Simulations of Exoplanet Radio Emission

We present calculations of auroral radio emission for an Earth-like planet produced by field-aligned current (FAC) driven electron acceleration using a coupled global magnetohydrodynamic (MHD) and inner magnetosphere model, extending the capabilities of previous works which focus solely on the direct transmission of magnetic energy between the stellar wind and ionosphere. Magnetized exoplanets are expected to produce radio emission via interaction between the host star's stellar wind and planetary magnetosphere-ionosphere system. The empirically derived Radiometric Bode's Law (RBL) is a linear relation between the magnetic solar wind power and total emitted radio power from magnetized Solar System planets, and is often extrapolated to extreme exoplanet systems. It has been shown that the magnitudes of the FACs coupling the stellar wind to planetary ionospheres are likely to be significantly limited (often referred to as ionospheric saturation), resulting in an estimated radio power up to several orders of magnitude less than that predicted by RBL. In this paper, we demonstrate the significance of intense, sporadic FACs, driven by nightside magnetic reconnection and inner magnetosphere plasma flow, to the total radio power produced by wind-ionosphere interaction in terrestrial planets. During periods of strong stellar wind variability, the contribution from these secondary currents can be over an order of magnitude greater than the primary current systems that previous models describe. The results highlight the role of the variability of the stellar wind on the magnitude and location of the resulting emission, subsequently affecting the conditions for detectability.

Keywords: solar-terrestrial interactions; magnetospheric radio emissions
The Spatial Distribution and Temperature of Mercury's Potassium Exosphere

Aside from the well-studied sodium doublet, the potassium D lines are the only optical emissions in Mercury's exosphere that are amply bright to contrast with the dayside disk. Measurements of the K exosphere are limited compared to Na, but the K regolith abundance is better constrained, so new insights may help to understand surface-exosphere coupling. We use imaging spectroscopy to map the K brightness over Mercury's evening hemisphere, which shows an enhancement at low to midlatitudes, well equatorward of the Na peak. Both Na and K are brighter in the south, but the ratio between northern and southern hemisphere K emission appears less symmetric than that of Na. The disk-averaged Na/K column density ratio is between 70 and 130. During the same night, the dayside emission was mapped, we used a high-resolution spectrograph to attempt to resolve the Na and K line widths on the nightside. Forward-modeling the alkaline line profiles with hyperfine structure gives Na D1 and D2 line widths of 1114 ± 50 K and 1211 ± 45 K, respectively. D2 may appear hotter solely because its higher opacity adds preferentially to the profile wings. The K line width is surprisingly cold and cannot be easily distinguished from the instrumental line width, even at R = 137,500. Line widths roughly constrain K gas between the surface temperature and 1000 K, making it the coldest metallic constituent of Mercury's exosphere. Although Na and K are chemical analogs and often assumed to have similar properties, the results herein illustrate quite different characteristics between these elements in Mercury's exosphere.

Keywords: spectroscopy; atomic spectroscopy; high resolution spectroscopy; mercury (planet); exosphere; planetary science; solar system astronomy; planetary atmospheres; atmospheric variability; planetary magnetospheres; optical telescopes
ROME. III. The Arecibo Search for Star-Planet Interactions at 5 GHz

After nearly three decades of discovery, many exoplanetary systems have been studied and characterized in detail with one important exception: exoplanet magnetism. Although many surveys sought to detect magnetospheric radio emissions from exoplanets to directly measure their magnetic field strengths, they have yet to reveal an unambiguous detection. However, the indirect detection of exoplanet magnetic fields by measuring their influence on their host stars via magnetic star-planet interactions has recently gained prominence as an alternative method of discovery. This third paper of the Radio Observations of Magnetized Exoplanets series presents the results of a targeted radio survey of eight nearby exoplanet-hosting systems that may engage in star-planet interactions. This survey, conducted with the Arecibo radio telescope at ~5 GHz, has the greatest frequency coverage of any to date while providing millijansky-level sensitivity over <1 s integration times. No exoplanet-induced stellar radio bursts were detected. The orbital phase coverage of candidate systems for magnetic star-planet interactions is described, and the survey results are examined within the context of the plasma flow-obstacle paradigm and searches for star-planet interactions at other wavelengths.

Keywords: star-planet interactions; exoplanets; non-thermal radiation sources; stellar activity; planetary magnetospheres; magnetospheric radio emissions
Comprehensive Analysis of a Symbiotic Candidate V503 Her

V503 Her was previously proposed as an eclipsing symbiotic candidate based on photometric behavior and spectroscopic appearance indicating the composite optical spectrum. To investigate its nature, we analyzed long-term photometric observations covering 100 yr of its photometric history and new low-resolution optical spectroscopic data, supplemented with the multifrequency measurements collected from several surveys and satellites. Based on the analysis presented in this paper, we claim that V503 Her is not an eclipsing binary star. The optical and infrared wavelengths are dominated by a K-type bright giant with an effective temperature of 4500 K, luminosity of 1900 L ⊙, and subsolar metallicity on the asymptotic giant branch showing semiregular complex multiperiodic pulsation behavior. V503 Her does not show the characteristics of strongly interacting symbiotic variables, but some pieces of evidence suggest that it could still be one of the "hidden" accreting-only symbiotic systems. However, the currently available data do not allow us to fully confirm or constrain the parameters of a possible companion.

Keywords: symbiotic binary stars; evolved stars; eclipsing binary stars; asymptotic giant branch stars; pulsating variable stars
The Anatomy of a Turbulent Radiative Mixing Layer: Insights from an Analytic Model with Turbulent Conduction and Viscosity

Turbulent radiative mixing layers (TRMLs) form at the interface of cold, dense gas and hot, diffuse gas in motion with each other. TRMLs are ubiquitous in and around galaxies on a variety of scales, including galactic winds and the circumgalactic medium. They host the intermediate-temperature gases that are efficient in radiative cooling, thus playing a crucial role in controlling the cold gas supply, phase structure, and spectral features of galaxies. In this work, we develop an intuitive analytic 1.5-dimensional model for TRMLs that includes a simple parameterization of the effective turbulent conductivity and viscosity and a piecewise power-law cooling curve. Our analytic model reproduces the mass flux, total cooling, and phase structure of 3D simulations of TRMLs at a fraction of the computational cost. It also reveals essential insights into the physics of TRMLs, particularly the importance of the viscous dissipation of relative kinetic energy in balancing radiative cooling as the shear Mach number approaches unity. This dissipation takes place both in the intermediate-temperature phase, which reduces the enthalpy flux from the hot phase, and in the cold phase, which enhances radiative cooling. Additionally, our model provides a fast and easy way of computing the column density and surface brightness of TRMLs, which can be directly linked to observations.

Keywords: circumgalactic medium; galactic winds; galaxies; galaxy evolution; galaxy physics; galactic and extragalactic astronomy
Identification and Parameter Determination of F-type Herbig Stars from LAMOST DR8

We identify 20 F-type Herbig stars and provide a list of 22 pre-main-sequence candidates from LAMOST DR8. The effective temperature, distance, extinction, stellar luminosity, mass, age, and radius are derived for each Herbig star based on optical spectra, photometry, Gaia EDR3 parallaxes, and pre-main-sequence evolutionary tracks. According to spectral energy distribution, 19 F-type Herbig stars belong to Class II YSOs, and one belongs to the flat-spectrum class. Four have Spitzer IRS spectra, of which three show extremely weak polycyclic aromatic hydrocarbon emissions, and three with both amorphous and crystalline silicate emissions share similar parameters and are at the same evolutionary stage. We detect a solar-nearby outbursting EXor Herbig star J034344.48+314309.3, a possible precursor of a Herbig Ae star. Intense emission lines of H I, He I, O I, Na I, and Ca II originating from the rapid accretion during the outbursts are detected in its optical spectra, and silicate emission features are detected in its infrared spectrum. We also conduct a statistical analysis of the disk properties of all known Herbig stars using the defined infrared spectral indices ( ${\alpha }_{J-{K}_{{\rm{S}}}}$ and ${\alpha }_{{K}_{{\rm{S}}}-W3}$ ). The proportion of Herbig stars with moderate infrared excesses decreases as effective temperature increases. The majority of the precursors (F, G, or K type) have moderate infrared excesses. Hotter Herbig stars tend to have a larger proportion with large infrared excesses. The trends may be due to the fact that hotter stars have larger areas of re-emitting dust, although there is some scatter due to the particularities of each disk.

Keywords: pre-main sequence stars; herbig ae/be stars; young stellar objects; star formation
Constraints on Europa's Water Group Torus from HST/COS Observations

In situ plasma measurements as well as remote mapping of energetic neutral atoms around Jupiter provide indirect evidence that an enhancement of neutral gas is present near the orbit of the moon Europa. Simulations suggest that such a neutral gas torus can be sustained by escape from Europa's atmosphere and consists primarily of molecular hydrogen, but the neutral gas torus has not yet been measured directly through emissions or in situ. Here we present observations by the Cosmic Origins Spectrograph (COS) of the Hubble Space Telescope (HST) from 2020 to 2021, which scanned the equatorial plane between 8 and 10 planetary radii west of Jupiter. No neutral gas emissions are detected. We derive upper limits on the emissions and compare these to modeled emissions from electron impact and resonant scattering using a Europa torus Monte Carlo model for the neutral gases. The comparison supports the previous findings that the torus is dilute and primarily consists of molecular hydrogen. A detection of sulfur ion emissions radially inward of the Europa orbit is consistent with emissions from the extended Io torus and with sulfur ion fractional abundances as previously detected.

Keywords: jovian satellites; europa; jupiter
Compressed Sensing Based RFI Mitigation and Restoration for Pulsar Signals

In pulsar signal processing, two primary difficulties are (1) radio-frequency interference (RFI) mitigation and (2) information loss due to preprocessing and mitigation itself. Linear mitigation methods have a difficulty in RFI modeling, and accommodate a limited range of RFI morphologies. Thresholding methods suffer from manual factors and adaptability. There is also a distinct lack of methods dedicated to information loss. In this paper, a novel method "CS-Pulsar" is proposed. It carries out compressed sensing (CS) on time-frequency signals to accomplish RFI mitigation and signal restoration simultaneously. Curvelets allow an optimal sparse representation for multichannel pulsar signals containing the time-of-arrival dispersion relationship. CS-Pulsar mitigation is implemented using a regularized least-squares framework that does not require the statistics of RFI to be known beforehand. CS-Pulsar implements channel restoration, and useful signal contents are retrieved from the measurement error by a morphological component analysis aided by the root-mean-square envelope. These two steps allow CS-Pulsar to provide key signal details for special astrophysical purposes. Experiments of signal restoration for pulsar data from the Nanshan 26 m radio telescope reveal the advantage of CS-Pulsar. The method successfully removes false peaks due to on-pulse RFI in multipeaked pulsar profiles. CS-Pulsar also increases the timing accuracy and signal-to-noise ratio proving its feasibilities and prospects in astrophysical measurements.

Keywords: radio pulsars; wavelet analysis; astronomy data modeling; astronomical techniques