adsabs/SciX_UAT_keywords huggingface dataset:
Kinematics of the Circumgalactic Medium of a z = 0.77 Galaxy from Mg II Tomography

Galaxy evolution is thought to be driven in large part by the flow of gas between galaxies and the circumgalactic medium (CGM), a halo of metal-enriched gas extending out to ≳100 kpc from each galaxy. Studying the spatial structure of the CGM holds promise for understanding these gas flow mechanisms; however, the common method of using background quasar sight lines provides minimal spatial information. Recent works have shown the utility of extended background sources such as giant gravitationally lensed arcs. Using background lensed arcs from the CSWA 38 lens system, we continuously probed, at a resolution element of about 15 kpc2, the spatial and kinematic distribution of Mg II absorption in a star-forming galaxy at z = 0.77 (stellar mass ≈109.7 M⊙, star formation rate ≈10 M⊙ yr-1) at impact parameters D ≃ 5-30 kpc. Our results present an anisotropic, optically thick medium whose absorption strength decreases with increasing impact parameter, in agreement with the statistics toward quasars and other gravitational arcs. Furthermore, we find generally low line-of-sight velocities in comparison to the relatively high velocity dispersion in the Mg II gas (with typical σ ≈ 50 km s-1). While the galaxy itself exhibits a clear outflow (with Mg II velocities up to ~500 km s-1) in the down-the-barrel spectrum, the outflow component is subdominant and only weakly detected at larger impact parameters probed by the background arcs. Our results provide evidence of mainly dispersion-supported, metal-enriched gas recycling through the CGM.

Keywords: circumgalactic medium; interstellar absorption; galaxy formation; galaxy fountains; galaxy winds
Energy Transport during 3D Small-scale Reconnection Driven by Anisotropic Plasma Turbulence

Energy dissipation in collisionless plasmas is a long-standing fundamental physics problem. Although it is well known that magnetic reconnection and turbulence are coupled and transport energy from system-size scales to subproton scales, the details of the energy distribution and energy dissipation channels remain poorly understood. Especially, the energy transfer and transport associated with 3D small-scale reconnection that occurs as a consequence of a turbulent cascade is unknown. We use an explicit fully kinetic particle-in-cell code to simulate 3D small-scale magnetic reconnection events forming in anisotropic and decaying Alfvénic turbulence. We identify a highly dynamic and asymmetric reconnection event that involves two reconnecting flux ropes. We use a two-fluid approach based on the Boltzmann equation to study the spatial energy transfer associated with the reconnection event and compare the power density terms in the two-fluid energy equations with standard energy-based damping, heating, and dissipation proxies. Our findings suggest that the electron bulk flow transports thermal energy density more efficiently than kinetic energy density. Moreover, in our turbulent reconnection event, the energy density transfer is dominated by plasma compression. This is consistent with turbulent current sheets and turbulent reconnection events, but not with laminar reconnection.

Keywords: solar magnetic reconnection; interplanetary turbulence
The LHS 1678 System: Two Earth-sized Transiting Planets and an Astrometric Companion Orbiting an M Dwarf Near the Convective Boundary at 20 pc

We present the Transiting Exoplanet Survey Satellite (TESS) discovery of the LHS 1678 (TOI-696) exoplanet system, comprised of two approximately Earth-sized transiting planets and a likely astrometric brown dwarf orbiting a bright (V J = 12.5, K s = 8.3) M2 dwarf at 19.9 pc. The two TESS-detected planets are of radius 0.70 ± 0.04 R ⊕ and 0.98 ± 0.06 R ⊕ in 0.86 day and 3.69 day orbits, respectively. Both planets are validated and characterized via ground-based follow-up observations. High Accuracy Radial Velocity Planet Searcher RV monitoring yields 97.7 percentile mass upper limits of 0.35 M ⊕ and 1.4 M ⊕ for planets b and c, respectively. The astrometric companion detected by the Cerro Tololo Inter-American Observatory/Small and Moderate Aperture Telescope System 0.9 m has an orbital period on the order of decades and is undetected by other means. Additional ground-based observations constrain the companion to being a high-mass brown dwarf or smaller. Each planet is of unique interest; the inner planet has an ultra-short period, and the outer planet is in the Venus zone. Both are promising targets for atmospheric characterization with the James Webb Space Telescope and mass measurements via extreme-precision radial velocity. A third planet candidate of radius 0.9 ± 0.1 R ⊕ in a 4.97 day orbit is also identified in multicycle TESS data for validation in future work. The host star is associated with an observed gap in the lower main sequence of the Hertzsprung-Russell diagram. This gap is tied to the transition from partially to fully convective interiors in M dwarfs, and the effect of the associated stellar astrophysics on exoplanet evolution is currently unknown. The culmination of these system properties makes LHS 1678 a unique, compelling playground for comparative exoplanet science and understanding the formation and evolution of small, short-period exoplanets orbiting low-mass stars.

Keywords: exoplanet systems; transit photometry; low mass stars; m dwarf stars; astrometric binary stars
Eridanus IV: an Ultra-faint Dwarf Galaxy Candidate Discovered in the DECam Local Volume Exploration Survey

We present the discovery of a candidate ultra-faint Milky-Way satellite, Eridanus IV (DELVE J0505-0931), detected in photometric data from the DECam Local Volume Exploration survey (DELVE). Eridanus IV is a faint (MV = - 4.7 ± 0.2), extended ( ${r}_{1/2}={75}_{-13}^{+16}\,\mathrm{pc}$ ), and elliptical (ϵ = 0.54 ± 0.1) system at a heliocentric distance of ${76.7}_{-6.1}^{+4.0}\,\mathrm{kpc}$ , with a stellar population that is well described by an old, metal-poor isochrone (age of τ ~ 13.0 Gyr and metallicity of [Fe/H] ≲ - 2.1 dex). These properties are consistent with the known population of ultra-faint Milky-Way satellite galaxies. Eridanus IV is also prominently detected using proper-motion measurements from Gaia Early Data Release 3, with a systemic proper motion of $({\mu }_{\alpha }\cos \delta ,{\mu }_{\delta })=(+0.25\pm 0.06,-0.10\pm 0.05)$ mas yr-1 measured from its horizontal branch and red-giant-branch member stars. We find that the spatial distribution of likely member stars hints at the possibility that the system is undergoing tidal disruption.

Keywords: dwarf galaxies; horizontal branch stars
Pixel-to-pixel Translation of Solar Extreme-ultraviolet Images for DEMs by Fully Connected Networks

In this study, we suggest a pixel-to-pixel image translation method among similar types of filtergrams such as solar extreme-ultraviolet (EUV) images. For this, we consider a deep-learning model based on a fully connected network in which all pixels of solar EUV images are independent of one another. We use six-EUV-channel data from the Atmospheric Imaging Assembly (AIA) on board the Solar Dynamics Observatory (SDO), of which three channels (17.1, 19.3, and 21.1 nm) are used as the input data and the remaining three channels (9.4, 13.1, and 33.5 nm) as the target data. We apply our model to representative solar structures (coronal loops inside of the solar disk and above the limb, coronal bright point, and coronal hole) in SDO/AIA data and then determine differential emission measures (DEMs). Our results from this study are as follows. First, our model generates three EUV channels (9.4, 13.1, and 33.5 nm) with average correlation coefficient values of 0.78, 0.89, and 0.85, respectively. Second, our model generates the solar EUV data with no boundary effects and clearer identification of small structures when compared to a convolutional neural network-based deep-learning model. Third, the estimated DEMs from AI-generated data by our model are consistent with those using only SDO/AIA channel data. Fourth, for a region in the coronal hole, the estimated DEMs from AI-generated data by our model are more consistent with those from the 50 frames stacked SDO/AIA data than those from the single-frame SDO/AIA data.

Keywords: the sun; solar instruments; solar atmosphere; solar extreme ultraviolet emission; neural networks
POWDERDAY: Dust Radiative Transfer for Galaxy Simulations

We present POWDERDAY (available at https://github.com/dnarayanan/powderday), a flexible, fast, open-source dust radiative transfer package designed to interface with both idealized and cosmological galaxy formation simulations. POWDERDAY builds on FSPS stellar population synthesis models, and HYPERION dust radiative transfer, and employs YT to interface between different software packages. We include our stellar population synthesis modeling on the fly, allowing significant flexibility in the assumed stellar physics and nebular line emission. The dust content follows either simple observationally motivated prescriptions (i.e., constant dust-to-metals ratios, or dust-to-gas ratios that vary with metallicity), direct modeling from galaxy formation simulations that include dust physics, as well as a novel approach that includes the dust content via learning-based algorithms from the SIMBA cosmological galaxy formation simulation. Active galactic nuclei (AGNs) can additionally be included via a range of prescriptions. The output of these models are broadband (912 Å-1 mm) spectral energy distributions (SEDs), as well as filter-convolved monochromatic images. POWDERDAY is designed to eliminate last-mile efforts by researchers that employ different hydrodynamic galaxy formation models and seamlessly interfaces with GIZMO, AREPO, GASOLINE, CHANGA, and ENZO. We demonstrate the capabilities of the code via three applications: a model for the star formation rate-infrared luminosity relation in galaxies (including the impact of AGNs), the impact of circumstellar dust around AGB stars on the mid-infrared emission from galaxy SEDs, and the impact of galaxy inclination angle on dust attenuation laws.

Keywords: galaxy evolution; galaxy luminosities; astronomy software; open source software; radiative transfer simulations
Photoionization of Nitrile-substituted Naphthalene and Benzene: Cation Spectroscopy, Photostability, and Implications for Photoelectric Gas Heating

We investigate the vacuum ultraviolet (VUV) photodynamics of gas phase 1- and 2-cyanonaphthalene and cyanobenzene, recently detected in the Taurus molecular cloud, by combining synchrotron radiation and a double imaging electron/ion coincidence setup. The high-resolution threshold photoelectron spectra (TPES) of all three molecules are obtained experimentally from which the adiabatic ionization energies are reported with very high accuracy, particularly for 2-cyanonaphthalene, for which no data exist at this level of precision. Theoretical calculations are performed to compare with the TPES for the ground electronic state of the cations. Furthermore, the different features observed in the extended TPES have been assigned to the different molecular orbitals with the help of the outer valence Green's function calculations. The present experiments also shed light on the kinetic energy distribution of the photoelectrons as a function of the incident photon energy, to describe their contribution to the photoelectric heating effect in the interstellar medium. In this context, we show how kinetic energy distributions can be obtained from our data for any given photon energy, such as the omnipresent Lyα line, or any given interstellar radiation field (ISRF). In addition, from the total ion yields, we estimate the photorates for a few ISRFs. Finally, we discuss the photodissociation of the two cyanonaphthalenes, quoting the activation energies of the dissociation channels with the help of Rice–Ramsperger–Kassel–Marcus modeling. It is observed that CN substitution does not cause any appreciable change to the VUV dissociative photoionization relaxation channel.

Keywords: interstellar medium; photoionization; photoelectron spectroscopy
ALMA View of the Infalling Envelope around a Massive Protostar in S255IR SMA1

The massive young stellar object S255IR NIRS3 embedded in the star-forming core SMA1 has been recently observed with a luminosity burst, which is conjectured as a disk-mediated variable accretion event. In this context, it is imperative to characterize the gas properties around the massive young stellar object. With this in mind, we carried out high angular resolution observations with the Atacama Large Millimeter/submillimeter Array and imaged the 900 μm dust continuum and the CH3CN J = 19-18 K = 0-10 transitions of S255IR SMA1. The integrated CH3CN emission exhibits an elongated feature with an extent of 1800 au in the northwest-southeast direction at a position angle of 165°, which is nearly perpendicular to the bipolar outflow. We confirm the presence of dense (a few $\times {10}^{9}$ cm-3) and hot (∼400 K) gas immediately surrounding the central protostar. The CH3CN emission features a velocity gradient along the elongated ridge, and by modeling the gas kinematics based on features in the position-velocity diagram, we infer that the gas is best described by a flattened rotating infalling envelope (or pseudo-disk). A mass infall rate of a few × 10-4 M⊙ yr-1 is derived. If there exists a putative Keplerian disk directly involved in the mass accretion onto the star and jet/outflow launching, it is likely smaller than 125 au and unresolved by our observations. We show qualitative resemblances between the gas properties (such as density and kinematics) in 255IR SMA1 inferred from our observations and those in a numerical simulation particularly tailored for studying the burst mode of massive star formation.

Keywords: star formation; protostars; accretion; submillimeter astronomy
Influence of Ionization on the Polytropic Index of the Solar Atmosphere within Local Thermodynamic Equilibrium Approximation

An initial theoretical attempt to explain the observed decrease of the polytropic/adiabatic index γ in the solar corona has been accomplished. The chemical reactions of the ionization–recombination processes in local thermodynamic equilibrium (LTE) of a solar plasma cocktail containing heavy elements are found to cause 1.1 < γ ≤ 5/3 in the quiet solar atmosphere. It is also shown that the quiet solar atmosphere is in LTE, justifying this theoretical study. This result is obtained by numerically solving the Saha equation and subsequently using a newly derived equation for calculation of the polytropic index from thermodynamic partial derivatives of the enthalpy and pressure with respect to density and temperature. In addition, a comparison measured from spectroscopic observations of propagating slow magnetohydrodynamic waves in coronal loops shows that LTE ionization accounts for a very small part of the observed decrease of γ, meaning that the solar plasma in the active region is not in LTE as expected. However, the observed dependency of higher polytropic index at higher temperatures is confirmed by the current theoretical approach. It is concluded that in order to account for the polytropic index decrease in the active regions of the solar corona, it is necessary for kinetic non-LTE ionization calculations to be performed.

Keywords: ionization; solar atmosphere; polytropes; chemical thermodynamics
A Multimodal Transfer Learning Method for Classifying Images of Celestial Point Sources

A large fraction of celestial objects exhibit point shapes in CCD images, such as stars and QSOs, which contain less information due to their few pixels. Point source classification based solely on image data may lead to low accuracy. To address this challenge, this paper proposes a Multi-modal Transfer Learning-based classification method for celestial objects with point shape images. Considering that spectral data possess rich features and that there is a correlation between spectral data and image data, the proposed approach fully utilizes the knowledge gained from celestial spectral data and transfers it to the original image-based classification, enhancing the accuracy of classifying stars and QSOs. Initially, a one-dimensional residual network is employed to extract a 128-dimensional spectral feature vector from the original 3700-dimensional spectral data. This spectral feature vector captures important features of the celestial object. The Generative Adversarial Network is then utilized to generate a simulated spectral vector of 128 dimensions, which corresponds to the celestial object image. By generating simulated spectral vectors, data from two modals (spectral and image) for the same celestial object are available, enriching the input features of the model. In the upcoming multimodal classification model, we only require the images of celestial objects along with their corresponding simulated spectral data, and we no longer need real spectral data. With the assistance of spectral data, the proposed method alleviates the above disadvantages of the original image-based classification method. Remarkably, our method has improved the F1-score from 0.93 to 0.9777, while reducing the error rate in classification by 40%. These enhancements significantly increase the classification accuracy of stars and QSOs, providing strong support for the classification of celestial point sources.

Keywords: classification; astronomy data analysis; dimensionality reduction
Neutrino-dominated Accretion Flows: A Second Nucleosynthesis Factory in Core-collapse Supernovae and Regulating the Iron Markets in Galaxies

Cosmic metals are widely believed to be produced by supernovae (SNe) and compact-object mergers. Here, we discuss the nucleosynthesis of neutrino-dominated accretion flows (NDAFs) with outflows in the centers of core-collapse SNe (CCSNe), and show that the outflows from NDAFs can have a significant contribution to the 56Ni abundances of faint explosions if the masses of the progenitor stars are within about 25-50 M⊙. Less-massive progenitor stars can produce more 56Ni than their more-massive counterparts in the NDAF outflow nucleosynthesis channel. Therefore, we find that the total (i.e., CCSNe and NDAF outflows) 56Ni mass per CCSN depends only weakly upon the mass of the progenitor star. In terms of metallicity evolution, the ratio of 56Fe (produced by the decay of 56Ni) mass to the initial total gas mass can increase by ~1.95 times if the upper limits of the nucleosynthesis yields from NDAF outflows and CCSNe are considered. Our results might have significant implications for the chemical evolution of the solar neighborhood, galaxies, and active galactic nuclei.

Keywords: accretion; black hole physics; galaxy chemical evolution; nucleosynthesis; supernovae
TXS 2116-077: A Gamma-Ray Emitting Relativistic Jet Hosted in a Galaxy Merger

What triggers collimated relativistic outflows or jets from the centers of galaxies remains a fundamental question in astrophysics. The merging of two galaxies has been proposed to realize the conditions to successfully launch and drive such jets into the intergalactic medium. However, evidence for the operation of this mechanism is scarce. Here we report the first unambiguous detection of an ongoing merger of a narrow-line Seyfert 1 galaxy, TXS 2116-077, hosting a closely aligned, γ-ray emitting relativistic jet with a Seyfert 2 galaxy at a separation of ∼12 kpc, using the observations taken with the 8.2 m Subaru Telescope. Our subsequent follow-up observations with the 10.4 m Gran Telescopio Canarias, 4.2 m William Herschel Telescope, and Chandra X-ray observatory have provided what is likely to be the first glimpse of the merging environment hosting a closely aligned relativistic jet. Our finding that the jet is considerably younger than the merger demonstrates that jet activity can be triggered by galaxy mergers and that γ-ray detected narrow-line Seyfert 1 galaxies represent the beginning phase of that activity. These results also highlight the crucial role of mergers in shaping the fate of galaxies in their cosmological evolution and are consistent with recent studies focused on the host galaxy imaging of this enigmatic class of active galactic nuclei.

Keywords: agn host galaxies; galaxy interactions; galaxy jets; relativistic jets; blazars
Photodissociation Branching Ratios of 13C16O in the Vacuum Ultraviolet Region from 102,745 to 106,360 cm-1

Direct branching ratio measurements for 13C16O are reported for the three lowest dissociation channels that produce C(3P)+O(3P), C(1D)+O(3P), and C(3P)+O(1D) in the vacuum ultraviolet (VUV) region from 102,745 cm-1 (97.33 nm) to 106,360 cm-1 (94.02 nm) and covering six 1Σ+ and six 1Π states. A time-slice velocity-map ion imaging apparatus with a tunable VUV laser source that is generated by the two-photon resonance-enhanced four-wave mixing technique is used to make these measurements. The results show that the substitution of 12C by 13C dramatically changes the photodissociation branching ratios into channels that produce C and O atoms in the excited 1D state for most of the absorption bands in the titled energy range. This isotope effect strongly depends on the specific rovibronic quantum states of CO that are being excited. The branching ratio data from the present study for 13C16O may significantly impact existing photochemical models because of the higher reactivity of the 1D states of the C and O atoms. In addition to this isotope effect, the rotational dependence of the branching ratios to high J' levels for several vibronic states has been determined. This provides useful information for unraveling the complicated predissociation dynamics of 13C16O.

Keywords: interstellar medium; photodissociation regions; solar system; molecule destruction
Searching for z > 6.5 Analogs Near the Peak of Cosmic Star Formation

Strong [O III]λλ4959,5007 + Hβ emission appears to be typical in star-forming galaxies at z > 6.5. As likely contributors to cosmic reionization, these galaxies and the physical conditions within them are of great interest. At z > 6.5, where Lyα is greatly attenuated by the intergalactic medium, rest-UV metal emission lines provide an alternative measure of redshift and constraints on the physical properties of star-forming regions and massive stars. We present the first statistical sample of rest-UV line measurements in z ∼ 2 galaxies selected as analogs of those in the reionization era based on [O III]λλ4959,5007 equivalent width (EW) or rest-frame U - B color. Our sample is drawn from the 3D-HST Survey and spans the redshift range $1.36\leqslant z\leqslant 2.49$ . We find that the median Lyα and C III]λλ1907,1909 EWs of our sample are significantly greater than those of z ∼ 2 UV-continuum-selected star-forming galaxies. Measurements from both individual and composite spectra indicate a monotonic, positive correlation between C III] and [O III], while a lack of trend is observed between Lyα and [O III] at EW[O III] ≲ 1000 Å. At higher EW[O III], extreme Lyα emission starts to emerge. Using stacked spectra, we find that Lyα and C III] are significantly enhanced in galaxies with lower metallicity. Two objects in our sample appear comparable to z > 6.5 galaxies with exceptionally strong rest-UV metal line emission. These objects have significant C IVλλ1548,1550, He IIλ1640, and O III]λλ1661,1665 emission in addition to intense Lyα or C III]. Detailed characterization of these lower-redshift analogs provides unique insights into the physical conditions in z > 6.5 star-forming regions, motivating future observations of reionization-era analogs at lower redshifts.

Keywords: high-redshift galaxies; h ii regions; emission line galaxies