adsabs/SciX_UAT_keywords huggingface dataset:
Atomic Gas Dominates the Baryonic Mass of Star-forming Galaxies at z ≈ 1.3

We present a comparison between the average atomic gas mass, <M Atom> (including hydrogen and helium), the average molecular gas mass, <M Mol>, and the average stellar mass, <M ⋆>, of a sample of star-forming galaxies at z ≈ 0.75-1.45 to probe the baryonic composition of galaxies in and during the epoch of peak star formation activity in the universe. The <M Atom> values of star-forming galaxies in two stellar-mass-matched samples at z = 0.74-1.25 and z = 1.25-1.45 were derived by stacking their HI 21 cm signals in the GMRT-CATz1 survey. We find that the baryonic composition of star-forming galaxies at z ≳ 1 is dramatically different from that at z ≈ 0. For star-forming galaxies with <M ⋆> ≈ 1010 M ⊙, the contribution of stars to the total baryonic mass, M Baryon, is ≈61% at z ≈ 0, but only ≈16% at z ≈ 1.3, while molecular gas constitutes ≈6% of the baryonic mass at z ≈ 0, and ≈14% at z ≈ 1.3. Remarkably, we find that atomic gas makes up ≈70% of M Baryon in star-forming galaxies at z ≈ 1.3. We find that the ratio <M Atom>/<M ⋆> is higher at both z ≈ 1.3 and at z ≈ 1.0 than in the local universe, with <M Atom>/<M ⋆> ≈ 1.4 at z ≈ 1.0 and ≈ 4.4 at z ≈ 1.3, compared to its value of ≈0.5 today. Further, we find that the ratio <M Atom>/<M Mol> in star-forming galaxies with <M ⋆> ≈ 1010 M ⊙ is ≈2.3 at z ≈ 1.0 and ≈5.0 at z ≈ 1.3. Overall, we find that atomic gas is the dominant component of the baryonic mass of star-forming galaxies at z ≈ 1.3, during the epoch of peak star formation activity in the universe.

Keywords: galaxies; high-redshift galaxies; neutral hydrogen clouds
The Turndown of the Baryonic Tully-Fisher Relation and Changing Baryon Fraction at Low Galaxy Masses

The ratio of baryonic-to-dark matter in present-day galaxies constrains galaxy formation theories and can be determined empirically via the baryonic Tully-Fisher relation (BTFR), which compares a galaxy's baryonic mass (M bary) to its maximum rotation velocity (V max). The BTFR is well determined at M bary > 108 M ⊙, but poorly constrained at lower masses due to small samples and the challenges of measuring rotation velocities in this regime. For 25 galaxies with high-quality data and M bary ≲ 108 M ⊙, we estimate M bary from infrared and H I observations and V max from the H I gas rotation. Many of the V max values are lower limits because the velocities are still rising at the edge of the detected H I disks (R max); consequently, most of our sample has lower velocities than expected from extrapolations of the BTFR at higher masses. To estimate V max, we map each galaxy to a dark matter halo assuming density profiles with and without cores. In contrast to noncored profiles, we find the cored profile rotation curves are still rising at R max values, similar to the data. When we compare the V max values derived from the cored density profiles to our M bary measurements, we find a turndown of the BTFR at low masses that is consistent with Λ cold dark matter predictions and implies baryon fractions of 1%-10% of the cosmic value. Although we are limited by the sample size and assumptions inherent in mapping measured rotational velocities to theoretical rotation curves, our results suggest that galaxy formation efficiency drops at masses below M bary ~ 108 M ⊙, corresponding to M 200 ~ 1010 M ⊙.

Keywords: dwarf irregular galaxies; galaxy formation; galaxy properties; scaling relations; galaxy kinematics
On Secular Gravitational Instability in Vertically Stratified Disks

Secular gravitational instability (GI) is one promising mechanism for explaining planetesimal formation. Previous studies of secular GI utilized a razor-thin disk model and derived the growth condition in terms of vertically integrated physical values such as dust-to-gas surface density ratio. However, in weakly turbulent disks where secular GI can operate, a dust disk can be orders of magnitude thinner than a gas disk, and analyses treating the vertical structures are necessary to clarify the interplay of the midplane dust motion and the upper gas motion. In this work, we perform vertically global linear analyses of secular GI with a vertical domain size of a few gas scale heights. We find that dust grains accumulate radially around the midplane while gas circulates over the whole vertical region. We obtain well-converged growth rates when the outer gas boundary is above two gas scale heights. The growth rates are underestimated if we assume the upper gas to be steady and regard it just as the source of external pressure to the dusty lower layer. Therefore, treating the upper gas motion is important even when the dust disk is much thinner than the gas disk. Conducting a parameter survey, we represent the growth condition in terms of the Toomre Q value for dust and dust-to-gas surface density ratio. The critical dust disk mass for secular GI is ~10-4 M * for a dust-to-gas surface density ratio of 0.01, a Stokes number of 0.1, and a radial dust diffusivity of 10-4 c s H, where c s is the gas sound speed, and H is the gas scale height.

Keywords: protoplanetary disks; hydrodynamics; astrophysical fluid dynamics
Multiwavelength Variation Phenomena of PKS 0735+178 on Diverse Timescales

The BL Lac object PKS 0735+178 has shown some complex multiwavelength variation phenomena in previous studies, especially in its color behavior. Bluer-when-brighter, redder-when-brighter, and achromatic behavior were all found to be possible long-term trends of PKS 0735+178. In this work, we collected long-term multiwavelength data on PKS 0735+178, and also performed a multicolor optical monitoring on intraday timescales. Intraday variability was detected on one night. On long timescales, a possible 22 day time lag was found between the R and γ-ray bands. The results of a cross-correlation analysis exhibited strong correlations between various optical bands on both intraday and long timescales. However, only a mild correlation was found between the long-term γ-ray and R-band light curves, which could be interpreted as different emission mechanisms for the γ-ray and optical emissions. PKS 0735+178 showed a significant harder-when-brighter (HWB) behavior in the γ-ray band, which is consistent with the observed optical bluer-when-brighter (BWB) trend on both long-term and intraday timescales. We found that the HWB and BWB trends will be enhanced during active states, especially for the historical low state. Such a phenomenon indicates a special activity-dependent color behavior of PKS 0735+178, and it could be well interpreted by the jet emission model.

Keywords: bl lacertae objects; active galaxies; galaxy photometry
True Polar Wander of Lava Worlds

As one of the most detectable types of terrestrial planets, lava worlds are highly prioritized targets for exoplanet atmosphere characterization since their atmospheres may reveal what they are made of and how. Our work examines the possibility of true polar wander (TPW) occurring on these ultrahot tidally locked planets, powered by mass redistribution from atmospheric flow between the hot permanent dayside and the cold permanent nightside. We find that lava planets within a certain mass and temperature range may undergo TPW, and this likelihood increases with star mass. As a result of TPW, the magma ocean and atmospheric compositions may be less evolved (refractory-enriched) than previously thought and may be validated by exoplanet demographic surveys.

Keywords: exoplanet evolution; exoplanet atmospheric evolution; exoplanet atmospheres
How Close are Compact Multiplanet Systems to the Stability Limit?

Transit surveys have revealed a significant population of compact multiplanet systems, containing several sub-Neptune-mass planets on close-in, tightly-packed orbits. These systems are thought to have formed through a final phase of giant impacts, which would tend to leave systems close to the edge of stability. Here, we assess this hypothesis, comparing observed eccentricities in systems exhibiting transit-timing variations versus the maximum eccentricities compatible with long-term stability. We use the machine-learning classifier SPOCK (Tamayo et al.) to rapidly classify the stability of numerous initial configurations and hence determine these stability limits. While previous studies have argued that multiplanet systems are often maximally packed, in the sense that they could not host any additional planets, we find that the existing planets in these systems have measured eccentricities below the limits allowed by stability by a factor of 2-10. We compare these results against predictions from the giant-impact theory of planet formation, derived from both N-body integrations and theoretical expectations that, in the absence of dissipation, the orbits of such planets should be distributed uniformly throughout the phase space volume allowed by stability. We find that the observed systems have systematically lower eccentricities than this scenario predicts, with a median eccentricity about four times lower than predicted. This suggests that, if these systems formed through giant impacts, then some dissipation must occur to damp their eccentricities. This may occur through interactions with the natal gas disk or a leftover population of planetesimals, or over longer timescales through the coupling of tidal and secular processes.

Keywords: exoplanet dynamics; exoplanet formation; exoplanet astronomy; celestial mechanics
C2N2 Vertical Profile in Titan's Stratosphere

In this paper, we present the first measurements of the vertical distribution of cyanogen ( ${{\rm{C}}}_{2}{{\rm{N}}}_{2}$ ) in Titan's lower atmosphere at different latitudes and seasons, using Cassini's Composite Infrared Spectrometer far-infrared data. We also study the vertical distribution of three other minor species detected in our data: methylacetylene ( ${{\rm{C}}}_{3}{{\rm{H}}}_{4}$ ), diacetylene ( ${{\rm{C}}}_{4}{{\rm{H}}}_{2}$ ), and ${{\rm{H}}}_{2}{\rm{O}}$ , in order to compare them to ${{\rm{C}}}_{2}{{\rm{N}}}_{2}$ , but also to get an overview of their seasonal and meridional variations in Titan's lower stratosphere from 85 km to 225 km. We measured an average volume mixing ratio of ${{\rm{C}}}_{2}{{\rm{N}}}_{2}$ of $6.2\pm 0.8\times {10}^{-11}$ at 125 km at the equator, but poles exhibit a strong enrichment in ${{\rm{C}}}_{2}{{\rm{N}}}_{2}$ (up to a factor 100 compared to the equator), greater than what was measured for ${{\rm{C}}}_{3}{{\rm{H}}}_{4}$ or ${{\rm{C}}}_{4}{{\rm{H}}}_{2}$ . Measuring ${{\rm{C}}}_{2}{{\rm{N}}}_{2}$ profiles provides constraints on the processes controlling its distribution, such as bombardment by Galactic Cosmic Rays which seem to have a smaller influence on ${{\rm{C}}}_{2}{{\rm{N}}}_{2}$ than predicted by photochemical models.

Keywords: saturnian satellites; planetary atmospheres; atmospheric composition; atmospheric variability; far infrared astronomy; spectroscopy
Limits on Mode Coherence in Pulsating DA White Dwarfs Due to a Nonstatic Convection Zone

The standard theory of pulsations deals with the frequencies and growth rates of infinitesimal perturbations in a stellar model. Modes that are calculated to be linearly driven should increase their amplitudes exponentially with time; the fact that nearly constant amplitudes are usually observed is evidence that nonlinear mechanisms inhibit the growth of finite-amplitude pulsations. Models predict that the mass of convection zones in pulsating hydrogen-atmosphere (DAV) white dwarfs is very sensitive to temperature (I.e., ${M}_{\mathrm{CZ}}\propto {T}_{\mathrm{eff}}^{-90}$ ), leading to the possibility that even low-amplitude pulsators may experience significant nonlinear effects. In particular, the outer turning point of finite-amplitude g-mode pulsations can vary with the local surface temperature, producing a reflected wave that is out of phase with what is required for a standing wave. This can lead to a lack of coherence of the mode and a reduction in its global amplitude. In this paper we show that (1) whether a mode is calculated to propagate to the base of the convection zone is an accurate predictor of its width in the Fourier spectrum, (2) the phase shifts produced by reflection from the outer turning point are large enough to produce significant damping, and (3) amplitudes and periods are predicted to increase from the blue edge to the middle of the instability strip, and subsequently decrease as the red edge is approached. This amplitude decrease is in agreement with the observational data while the period decrease has not yet been systematically studied.

Keywords: white dwarf stars; da stars; computational methods; stellar oscillations; analytical mathematics; stellar interiors
A Pair of Tidally Disrupted Galaxies from The Hubble Legacy Archive

We describe archival, serendipitously obtained Hubble Space Telescope (HST) observations of a tidally disturbed galaxy pair (AM 0436-472 NED01/LEDA 503707) located at z = 0.058 (240 Mpc). The system likely belongs to peculiar ring galaxies of Solitaire type. We also analyze an archival optical spectrum of AM 0436-472 NED01 and report an upper limit in X-rays (0.2-10 keV).

Keywords: galaxies; galaxy interactions
Pulsational Pair-instability and the Mass Gap of Population III Black Holes: Effects of Overshooting

Since the discovery of GW190521, several proposals have been put forward to explain the formation of a black hole (BH) in the mass gap caused by (pulsational) pair-instability (PPI), M = 65-130 M⊙. We calculate the mass ejection of Population III stars by the PPI process using a stellar evolution and hydrodynamical code. If a relatively small, but reasonable, value is adopted for the overshooting parameter, the stars do not become red supergiants during the PPI phase. We show that in this case most of the hydrogen envelope remains after the mass ejection by PPI. We find that the BH mass could be at most around 110 M⊙ below the mass range of pair-instability supernovae.

Keywords: stellar evolution; massive stars; stellar mass loss; population iii stars; black holes
The Internal Line-of-Sight Kinematics of NGC 346: The Rotation of the Core Region

We present the stellar radial velocity analysis of the central $1^{\prime} \times 1^{\prime} $ of the young massive Small Magellanic Cloud star cluster NGC 346. Using VLT/MUSE integral field spectroscopy in combination with Hubble Space Telescope photometry, we extract 103 spectra of cluster member stars suited to measure accurate line-of-sight kinematics. The cluster member stars show two distinct velocity groups at ${v}_{1}=-{3.3}_{-0.2}^{+0.3}\,\mathrm{km}\,{{\rm{s}}}^{-1}$ and ${v}_{2}={2.6}_{-0.1}^{+0.1}\,\mathrm{km}\,{{\rm{s}}}^{-1}$ , relative to the systemic velocity of (165.5 ± 0.2) km s-1, and hint at a third group at ${v}_{3}={9.4}_{-0.1}^{+0.1}\,\mathrm{km}\,{{\rm{s}}}^{-1}$ . We show that there is neither a correlation between the velocity groups and the spatial location of the stars, nor their locus on optical color-magnitude diagrams, which makes the stellar velocity a key parameter to separate individual stellar components in such a young star cluster. Velocity group 2 shows clear rotation with Ω2 =(-0.4 ± 0.1) Myr-1, corresponding to (-4.9 ± 0.7) km s-1 at radial distance of 10 pc from the center, a possible remnant of the formation process of NGC 346 through the hierarchical collapse of the giant molecular cloud. The ionizing gas has lost any natal kinematic imprint and shows clear expansion, driven by far-ultraviolet fluxes and stellar winds of the numerous OB stars in the cluster center. The size of this expanding bubble and its expansion velocity of 7.9 km s-1 are in excellent agreement with the estimate that the latest star formation episode occurred about two million years ago.

Keywords: young star clusters; small magellanic cloud; radial velocity; stellar kinematics; spectroscopy
SPORK That Spectrum: Increasing Detection Significances from High-resolution Exoplanet Spectroscopy with Novel Smoothing Algorithms

Spectroscopic studies of planets outside of our own solar system provide some of the most crucial information about their formation, evolution, and atmospheric properties. In ground-based spectroscopy, the process of extracting the planets signal from the stellar and telluric signal has proven to be the most difficult barrier to accurate atmospheric information. However, with novel normalization and smoothing methods, this barrier can be minimized and the detection significance dramatically increased over existing methods. In this paper, we take two examples of CRIRES emission spectroscopy taken of HD 209458 b and HD 179949 b, and apply SPORK (SPectral cOntinuum Refinement for telluriKs) and iterative smoothing to boost the detection significance from 5.78 to 9.71σ, and from 4.38σ to 6.89σ, respectively. These methods, which largely address systematic quirks introduced by imperfect detectors or reduction pipelines, can be employed in a wide variety of scenarios, from archival data sets to simulations of future spectrographs.

Keywords: hot jupiters; high resolution spectroscopy; exoplanet atmospheres
Detailed Calculations of the Efficiency of Planetesimal Accretion in the Core-accretion Model

We present the results of a study of the accretion rate of planetesimals by a growing proto-Jupiter in the core-accretion model. The purpose of our study is to test the assumptions of Pollack et al. regarding the flux of planetesimals and their encounter velocities with the protoplanet. Using a newly developed code, we have accurately calculated planetesimals trajectories during their passage in the envelope by combining detailed three-body integrations with gas drag. To be consistent with Pollack et al., our calculations do not include the effect of nebular gas. The results point to several new findings. For instance, we find that only 4-5 M⊕ is accreted in the first 1.5 Myr before the onset of rapid gas accretion and ∼10 M⊕ is accreted simultaneously during this phase. We also find that mass accretion remains small (0.3-0.4 M⊕) for ∼1 Myr after this time. This late accretion, together with a rapid infall of gas, could lead to a mixing of accreted material throughout the outer regions, which may explain the enhancement of high-Z material in Jupiter's envelope. Results demonstrate that planetesimal encounters with the protoplanetary envelope become so fast that in most cases, ram pressure breaks them up. As a result, the accretion rate is largely independent of the planetesimals' size and composition. We also carried out some calculations considering nebular gas drag. As expected, the accreted mass of planetesimals depended strongly on their size and composition. In general, nebular gas lowered the amount of accreted planetesimals, although the majority of planetesimals were still accreted during the rapid gas accretion phase.

Keywords: jupiter; planet formation; planetesimals
First Results from the JWST Early Release Science Program Q3D: Turbulent Times in the Life of a z 3 Extremely Red Quasar Revealed by NIRSpec IFU

Extremely red quasars, with bolometric luminosities exceeding 1047 erg s-1, are a fascinating high-redshift population that is absent in the local universe. They are the best candidates for supermassive black holes accreting at rates at or above the Eddington limit, and they are associated with the most rapid and powerful outflows of ionized gas known to date. They are also hosted by massive galaxies. Here we present the first integral field unit observations of a high-redshift quasar obtained by the Near Infrared Spectrograph on board the James Webb Space Telescope (JWST), which targeted SDSS J165202.64+172852.3, an extremely red quasar at z = 2.94. The JWST observations reveal extended ionized gas-as traced by [O III] λ5007 Å-in the host galaxy of the quasar, its outflow, and the circumgalactic medium. The complex morphology and kinematics imply that the quasar resides in a very dense environment with several interacting companion galaxies within projected distances of 10-15 kpc. The high density of the environment and the large velocities of the companion galaxies suggest that this system may represent the core of a forming cluster of galaxies. The system is a good candidate for a merger of two or more dark matter halos, each with a mass of a few 1013 M ⊙, and potentially traces one of the densest knots at z ~ 3.

Keywords: active galaxies; quasars; james webb space telescope; emission line galaxies; protoclusters; galaxy spectroscopy
Early Galaxy Formation and the Hubble Constant Tension

Tension between local determinations of the Hubble constant and the value found in fits to the cosmic microwave background (CMB) acoustic power spectrum have emerged as finer angular scales (higher multipoles ℓ) have been measured in the latter. Independent observations indicate that massive galaxies emerged at higher redshift than anticipated in the standard ΛCDM structure formation paradigm. If genuine, these early galaxies would cause excess gravitational lensing of the CMB, adding an anomalous source of power at high ℓ. I suggest that accommodating this anomalous source of power in multiparameter fits might be the root cause of the Hubble tension rather than systematics in local measurements.

Keywords: cosmic microwave background radiation; galaxy formation; hubble constant
How Nested Bars Enhance, Modulate, and Are Destroyed by Gas Inflows

Gas flows in the presence of two independently rotating nested bars remain not fully understood but are likely to play an important role in fueling the central black hole. We use high-resolution hydrodynamical simulations with detailed models of subgrid physics to study this problem. Our results show that the inner bar in double-barred galaxies can help drive gas flow from the nuclear ring to the center. In contrast, gas inflow usually stalls at the nuclear ring in single-barred galaxies. The inner bar causes a quasiperiodic inflow with a frequency determined by the difference between the two bar pattern speeds. We find that the star formation rate is higher in the model with two bars than in that with one bar. The inner bar in our model gradually weakens and dissolves due to gas inflow over a few billion years. Star formation produces metal-rich/α-poor stars, which slows the weakening of the inner bar but does not halt its eventual decay. We also present a qualitative comparison of the gas morphology and kinematics in our simulations with those of observed double-barred galaxies.

Keywords: barred spiral galaxies; interstellar medium; hydrodynamical simulations; galaxy evolution; stellar feedback; active galactic nuclei; galaxy nuclei