adsabs/SciX_UAT_keywords huggingface dataset:
The Detectability and Constraints of Biosignature Gases in the Near- and Mid-infrared from Transit Transmission Spectroscopy

The James Webb Space Telescope is expected to revolutionize our understanding of Jovian worlds over the coming decade. However, as we push toward characterizing cooler, smaller, terrestrial-like planets, dedicated next-generation facilities will be required to tease out the small spectral signatures indicative of biological activity. Here, we evaluate the feasibility of determining atmospheric properties, from near-to-mid-infrared transmission spectra, of transiting temperate terrestrial M-dwarf companions. Specifically, we utilize atmospheric retrievals to explore the trade space between spectral resolution, wavelength coverage, and signal-to-noise on our ability to both detect molecular species and constrain their abundances. We find that increasing spectral resolution beyond R = 100 for near-infrared wavelengths, shorter than 5 μm, proves to reduce the degeneracy between spectral features of different molecules and thus greatly benefits the abundance constraints. However, this benefit is greatly diminished beyond 5 μm as any overlap between broad features in the mid-infrared does not deconvolve with higher resolutions. Additionally, our findings revealed that the inclusion of features beyond 11 μm did not meaningfully improve the detection significance or the abundance constraints results. We conclude that an instrument with continuous wavelength coverage from ∼2 to 11 μm, spectral resolution of R ≃ 50-300, and a 25 m2 collecting area, would be capable of detecting H2O, CO2, CH4, O3, and N2O in the atmosphere of an Earth-analog transiting a M dwarf (magK = 8.0) within 50 transits, and obtain better than an order-of-magnitude constraint on each of their abundances.

Keywords: exoplanet atmospheres; exoplanet atmospheric composition; habitable planets; exoplanets; spectroscopy; molecular spectroscopy; near infrared astronomy; infrared astronomy; bayesian statistics; biosignatures
The Next Generation Virgo Cluster Survey (NGVS). XXXV. First Kinematical Clues of Overly Massive Dark Matter Halos in Several Ultradiffuse Galaxies in the Virgo Cluster

We present Keck/DEIMOS spectroscopy of the first complete sample of ultradiffuse galaxies (UDGs) in the Virgo cluster. We select all UDGs in Virgo that contain at least 10 globular cluster (GC) candidates and are more than 2.5σ outliers in scaling relations of size, surface brightness, and luminosity (a total of 10 UDGs). We use the radial velocity of their GC satellites to measure the velocity dispersion of each UDG. We find a mixed bag of galaxies, from one UDG that shows no signs of dark matter, to UDGs that follow the luminosity-dispersion relation of early-type galaxies, to the most extreme examples of heavily dark matter-dominated galaxies that break well-known scaling relations such as the luminosity-dispersion or U-shaped total mass-to-light ratio relations. This is indicative of a number of mechanisms at play forming these peculiar galaxies. Some of them may be the most extended version of dwarf galaxies, while others are so extreme that they seem to populate dark matter halos consistent with that of the Milky Way or even larger. Even though Milky Way stars and other GC interlopers contaminating our sample of GCs cannot be fully ruled out, our assessment of this potential problem and simulations indicate that the probability is low and, if present, unlikely to be enough to explain the extreme dispersions measured. Further confirmation from stellar kinematics studies in these UDGs would be desirable. The lack of such extreme objects in any of the state-of-the-art simulations opens an exciting avenue of new physics shaping these galaxies.

Keywords: low surface brightness galaxies; early-type galaxies; dwarf galaxies; galaxy evolution; globular star clusters; virgo cluster; dark matter; galaxy dark matter halos
Two-component Magnetic Field along the Line of Sight to the Perseus Molecular Cloud: Contribution of the Foreground Taurus Molecular Cloud

Optical stellar polarimetry in the Perseus molecular cloud direction is known to show a fully mixed bimodal distribution of position angles across the cloud. We study the Gaia trigonometric distances to each of these stars and reveal that the two components in position angles trace two different dust clouds along the line of sight. One component, which shows a polarization angle of -37°6 ± 35°2 and a higher polarization fraction of 2.0 ± 1.7 %, primarily traces the Perseus molecular cloud at a distance of 300 pc. The other component, which shows a polarization angle of +66°8 ± 19°1 and a lower polarization fraction of 0.8 ± 0.6 %, traces a foreground cloud at a distance of 150 pc. The foreground cloud is faint, with a maximum visual extinction of ≤1 mag. We identify that foreground cloud as the outer edge of the Taurus molecular cloud. Between the Perseus and Taurus molecular clouds, we identify a lower-density ellipsoidal dust cavity with a size of 100-160 pc. This dust cavity is located at l = 170°, b = -20°, and d = 240 pc, which corresponds to an HI shell generally associated with the Per OB2 association. The two-component polarization signature observed toward the Perseus molecular cloud can therefore be explained by a combination of the plane-of-sky orientations of the magnetic field both at the front and at the back of this dust cavity.

Keywords: interstellar clouds; starlight polarization; interstellar magnetic fields; polarimetry
Optical Constants of a Titan Haze Analog from 0.4 to 3.5 μm Determined Using Vacuum Spectroscopy

Titan's thick atmosphere is primarily composed of nitrogen and methane. Complex chemistry happening in Titan's atmosphere produces optically thick organic hazes. These hazes play significant roles in Titan's atmosphere and on its surface, and their optical properties are crucial for understanding many processes happening on Titan. Due to the lack of such information, the optical constants of laboratory-prepared Titan haze analogs are essential inputs for atmospheric modeling and data analysis of remote-sensing observations of Titan. Here we perform laboratory simulations in a Titan-relevant environment, analyze the resulting Titan haze analogs using vacuum Fourier transform infrared spectroscopy, and calculate the optical constants from the measured transmittance and reflectance spectra. We provide a reliable set of optical constants of Titan haze analogs in the wavelength range from 0.4 to 3.5 μm and will extend it to 28.5 μm in the near future, which can be used for analyzing both existing and future observational data of Titan. This study establishes a feasible method to determine optical constants of haze analogs of (exo)planetary bodies.

Keywords: titan
Beyond Runaway: Initiation of the Post-runaway Greenhouse State on Rocky Exoplanets

The runaway greenhouse represents the ultimate climate catastrophe for rocky, Earth-like worlds: when the incoming stellar flux cannot be balanced by radiation to space, the oceans evaporate and exacerbate heating, turning the planet into a hot wasteland with a steam atmosphere overlying a possibly molten magma surface. The equilibrium state beyond the runaway greenhouse instellation limit depends on the radiative properties of the atmosphere and its temperature structure. Here, we use 1D radiative-convective models of steam atmospheres to explore the transition from the tropospheric radiation limit to the post-runaway climate state. To facilitate eventual simulations with 3D global circulation models, a computationally efficient band-gray model is developed, which is capable of reproducing the key features of the more comprehensive calculations. We analyze two factors that determine the equilibrated surface temperature of post-runaway planets. The infrared cooling of the planet is strongly enhanced by the penetration of the dry adiabat into the optically thin upper regions of the atmosphere. In addition, thermal emission of both shortwave and near-IR fluxes from the hot lower atmospheric layers, which can radiate through window regions of the spectrum, is quantified. Astronomical surveys of rocky exoplanets in the runaway greenhouse state may discriminate these features using multiwavelength observations.

Keywords: extrasolar rocky planets; exoplanet atmospheres; greenhouse gases; habitable planets
The ALMA REBELS Survey: Average [C II] 158 μm Sizes of Star-forming Galaxies from z 7 to z 4

We present the average [C II] 158 μm emission line sizes of UV-bright star-forming galaxies at z ~ 7. Our results are derived from a stacking analysis of [C II] 158 μm emission lines and dust continua observed by the Atacama Large Millimeter/submillimeter Array (ALMA), taking advantage of the large program Reionization Era Bright Emission Line Survey. We find that the average [C II] emission at z ~ 7 has an effective radius r e of 2.2 ± 0.2 kpc. It is ≳2× larger than the dust continuum and the rest-frame UV emission, in agreement with recently reported measurements for z ≲ 6 galaxies. Additionally, we compared the average [C II] size with 4 < z < 6 galaxies observed by the ALMA Large Program to INvestigate [C II] at Early times (ALPINE). By analyzing [C II] sizes of 4 < z < 6 galaxies in two redshift bins, we find an average [C II] size of r e = 2.2 ± 0.2 kpc and r e = 2.5 ± 0.2 kpc for z ~ 5.5 and z ~ 4.5 galaxies, respectively. These measurements show that star-forming galaxies, on average, show no evolution in the size of the [C II] 158 μm emitting regions at redshift between z ~ 7 and z ~ 4. This finding suggests that the star-forming galaxies could be morphologically dominated by gas over a wide redshift range.

Keywords: high-redshift galaxies; interstellar medium; submillimeter astronomy
Generalized General Relativistic Magnetohydrodynamic Equations for Plasmas of Active Galactic Nuclei in the Era of the Event Horizon Telescope

The generalized general relativistic magnetohydrodynamic (generalized GRMHD) equations have been used to study specific relativistic plasma phenomena, such as relativistic magnetic reconnection or wave propagation modified by nonideal MHD effects. However, the Θ term in the generalized Ohm's law, which expresses the energy exchange between two fluids composing a plasma, has yet to be determined in these equations. In this paper, we determine the Θ term based on the generalized relativistic Ohm's law itself. This provides closure of the generalized GRMHD equations, yielding a closed system of the equations of relativistic plasma. According to this system of equations, we reveal the characteristic scales of nonideal MHD phenomena and clarify the applicable condition of the ideal GRMHD equations. We evaluate the characteristic scales of the nonideal MHD phenomena in the M87* plasma using the Event Horizon Telescope observational data.

Keywords: black hole physics; plasma physics; general relativity; magnetic fields; active galactic nuclei; high energy astrophysics
E+A Galaxy Candidates in and around the Virgo Cluster

E+A galaxies are post-starburst galaxies that have recently undergone complete quenching of their star formation, making them a valuable source for studying the evolution of galaxies and their environments. Using the Extended Virgo Cluster Catalog, we manually identified 125 "green" and 24 "blue" E+A galaxy candidates within the Virgo Cluster based on their spectral shape, u - r color, lack of Hα emission, and hydrogen Balmer absorption. Interestingly, we found a higher density of E+A galaxy candidates in the Virgo Cluster than that of most other low-redshift clusters, and several regions of particularly high E+A density within the Virgo Cluster. The large number of E+As in and around the Virgo Cluster hints at the influence of a dense galaxy environment on the formation of E+A galaxies, and the potential value of E+A galaxies as a diagnostic tool to study the evolution of clusters.

Keywords: galaxy evolution; virgo cluster; post-starburst galaxies; e+a galaxies; galaxy quenching
A 3D Parametric Venusian Bow Shock Model with the Effects of Mach Number and Interplanetary Magnetic Field

Using global magnetohydrodynamics simulations, we have developed a three-dimensional parametric model for the Venusian bow shock based on a generalized conic section function defined by six parameters, with the effects of the solar wind magnetosonic Mach number (M MS) and the interplanetary magnetic field (IMF) involved. The parametric model's results reveal the following findings: (1) The size of the Venusian bow shock is primarily determined by M MS. An increase in M MS results in the bow shock moving closer to Venus and a reduction in its flaring angle. (2) Both the subsolar standoff distance and the bow shock's flaring angle increase with the strength of the IMF components that are perpendicular to the solar wind flow direction (B Y and B Z in the Venus-centered solar orbital coordinate system), whereas the parallel IMF component (B X ) has a limited impact on the subsolar standoff distance but affects the flaring angle. (3) The cross section of the bow shock is elongated in the direction perpendicular to the IMF on the Y–Z plane, and the elongation degree is enhanced with increasing intensities of B Y and B Z . (4) The quasi-parallel bow shock locates closer to the planet as compared to the quasi-perpendicular bow shock. These findings are in alignment with prior empirical and theoretical models. The influences of M MS and IMF on the bow shock's position and geometry are attributed to the propagation of fast magnetosonic waves, showing the nature of the formation of a collisionless bow shock under the interaction of magnetized flow with an atmospheric object.

Keywords: magnetohydrodynamics; planetary bow shocks; solar-planetary interactions; venus
Expectations of the Size Evolution of Massive Galaxies at 3 ≤ z ≤ 6 from the TNG50 Simulation: The CEERS/JWST View

We present a catalog of about 25,000 images of massive (M ⋆ ≥ 109 M ⊙) galaxies at redshifts 3 ≤ z ≤ 6 from the TNG50 cosmological simulation, tailored for observations at multiple wavelengths carried out with JWST. The synthetic images were created with the SKIRT radiative transfer code, including the effects of dust attenuation and scattering. The noiseless images were processed with the mirage simulator to mimic the Near Infrared Camera (NIRCam) observational strategy (e.g., noise, dithering pattern, etc.) of the Cosmic Evolution Early Release Science (CEERS) survey. In this paper, we analyse the predictions of the TNG50 simulation for the size evolution of galaxies at 3 ≤ z ≤ 6 and the expectations for CEERS to probe that evolution. In particular, we investigate how sizes depend on the wavelength, redshift, mass, and angular resolution of the images. We find that the effective radius accurately describes the three-dimensional half-mass-radius of the TNG50 galaxies. Sizes observed at 2 μm are consistent with those measured at 3.56 μm at all redshifts and masses. At all masses, the population of higher-z galaxies is more compact than their lower-z counterparts. However, the intrinsic sizes are smaller than the mock observed sizes for the most massive galaxies, especially at z ≲ 4. This discrepancy between the mass and light distributions may point to a transition in the galaxy morphology at z = 4-5, where massive compact systems start to develop more extended stellar structures. 22 22 Data publicly released at https://www.tng-project.org/costantin22.

Keywords: galaxies; galactic and extragalactic astronomy; high-redshift galaxies; late-type galaxies; irregular galaxies; galaxy classification systems; magnetohydrodynamical simulations; radiative transfer simulations
Preemergence Signatures of Horizontal Divergent Flows in Solar Active Regions

Solar active regions (ARs) play a fundamental role in driving many of the geoeffective eruptions, which propagate into the solar system. However, we are still unable to consistently predict where and when ARs will occur across the solar disk by identifying preemergence signatures in observables such as the Doppler velocity (without using helioseismic methods). Here we aim to determine the earliest time at which preemergence signatures, the horizontal divergent flow (HDF) in particular, can be confidently detected using data from the Solar Dynamics Observatory's Helioseismic and Magnetic Imager. Initially, we follow previous studies using the thresholding method, which searches for significant increases in the number of pixels that display a specific line-of-sight velocity. We expand this method to more velocity windows and conduct a basic parameter study investigating the effect of cadence on the inferred results. Our findings agree with previous studies with 37.5% of ARs displaying an HDF, with average lead times between the HDF and flux emergence of 58 minutes. We present a new potential signature of flux emergence, which manifests as cadence-independent transient disruptions to the amplitudes of multiple velocity windows and recover potential preemergence signatures for 10 of the 16 ARs studied, with lead times of 60-156 minutes. Several effects can influence both the estimated times of both HDF and flux emergence suggesting that one may need to combine Doppler and magnetic field data to get a reliable indicator of continued flux emergence.

Keywords: solar magnetic flux emergence; solar active regions; solar active region magnetic fields; solar active region velocity fields
Massive White Dwarfs in Young Star Clusters

We have carried out a search for massive white dwarfs (WDs) in the direction of young open star clusters using the Gaia DR2 database. The aim of this survey was (1) to provide robust data for new and previously known high-mass WDs regarding cluster membership, (2) to highlight WDs previously included in the initial final mass relation (IFMR) that are unlikely members of their respective clusters according to Gaia astrometry, and (3) to select an unequivocal WD sample that could then be compared with the host clusters' turnoff masses. All promising WD candidates in each cluster color-magnitude diagram were followed up with spectroscopy from Gemini in order to determine whether they were indeed WDs and derive their masses, temperatures, and ages. In order to be considered cluster members, white dwarfs were required to (1) have proper motions and parallaxes within 2σ, 3σ, or 4σ of those of their potential parent cluster based on how contaminated the field was in their region of the sky, (2) have a cooling age that was less than the cluster age, and (3) have a mass that was broadly consistent with the IFMR. A number of WDs included in current versions of the IFMR turned out to be nonmembers, and a number of apparent members, based on Gaia's astrometric data alone, were rejected, as their mass and/or cooling times were incompatible with cluster membership. In this way, we developed a highly selected IFMR sample for high-mass WDs that, surprisingly, contained no precursor masses significantly in excess of ∼ 6 M⊙.

Keywords: white dwarf stars; chandrasekhar limit; supernovae; compact objects; open star clusters; young star clusters
On the Recent Discovery of Coronal [Fe X]λ6374 Emission in the Low-metallicity Dwarf Galaxy SDSS J0944-0038

Coronal emission lines, especially the [Fe X]λ6374 line, are now being used as tracers for intermediate mass black holes (IMBHs) in low-mass galaxies. We show that the recent discovery of [Fe X]λ6374 emission in the metal-poor starburst SDSS J094401.87-003832.1 by Reefe et al. is, in fact, a misidentified line. The line interpreted as [Fe X]λ6374 is Si II λ6371. We caution that current and future campaigns hunting for IMBHs with the [Fe X]λ6374 line need to account for possible contamination by Si II λ6371 emission.

Keywords: emission line galaxies; dwarf irregular galaxies
Minute-timescale Variability in the X-ray Emission of the Highest Redshift Blazar

We report on two Chandra observations of the quasar PSO J0309+27, the most distant blazar observed so far (z = 6.1), performed eight months apart, in 2020 March and November. Previous Swift-XRT observations showed that this object is one of the brightest X-ray sources beyond redshift 6.0 ever observed so far. This new dataset confirmed the high flux level and unveiled a spectral change that occurred on a very short timescale (250 s rest frame), caused by a significant softening of the emission spectrum. This kind of spectral variability, on such a short interval, has never been reported in the X-ray emission of a flat-spectrum radio quasar. A possible explanation for this is given by the emission produced by the inverse Compton scatter of the quasar UV photons by the cold electrons present in a fast shell moving along the jet. Although this bulk Comptonization emission should be an unavoidable consequence of the standard leptonic jet model, this would be the first time that it has been observed. * ...

Keywords: blazars; flat-spectrum radio quasars; radio loud quasars; jets; quasars
GRB 221009A: A Light Dark Matter Burst or an Extremely Bright Inverse Compton Component?

Gamma-ray bursts (GRBs) have been considered as potential very high energy photon emitters due to the large amount of energy released as well as the strong magnetic fields involved in their jets. However, the detection of teraelectronvolt photons is not expected from bursts beyond a redshift of z ≳ 0.1, due to their attenuation with the extragalactic background light (EBL). For these reasons, the recent observation of photons with energies of 18 and 251 TeV from GRB 221009A (z = 0.151) last 2022 October 9 has challenged what we know about the teraelectronvolt-emission mechanisms and the extragalactic background. In order to explain the teraelectronvolt observations, recent works exploring candidates of dark matter have started to appear. In this paper, we discuss the required conditions and limitations within the most plausible scenario, synchrotron self-Compton radiation in the GRB afterglow, to interpret the one 18 TeV photon observation besides the EBL. To avoid the Klein-Nishina effect, we find an improbable value of the microphysical magnetic parameter below 10-6 for a circumburst medium value >1 cm-3 (expected in the collapsar scenario). Therefore, we explore possible scenarios in terms of axion-like particles (ALPs) and dark photon mechanisms to interpret this highly energetic photon and we discuss the implications in the GRB energetics. We find that the ALPs and dark photon scenarios can explain the 18 teraelectronvolt photon but not the 251 teraelectronvolt photon.

Keywords: dark matter; high energy astrophysics; gamma-ray bursts