adsabs/SciX_UAT_keywords huggingface dataset:
The Pairing Probability of Massive Black Holes in Merger Galaxies in the Presence of Radiative Feedback

Dynamical friction (DF) against stars and gas is thought to be an important mechanism for orbital evolution of massive black holes (MBHs) in merger remnant galaxies. Recent theoretical investigations, however, show that DF does not always lead to MBH inspiral. For MBHs evolving in gas-rich backgrounds, the ionizing radiation that emerges from the innermost parts of their accretion flow can affect the surrounding gas in such a way to cause the MBHs to accelerate and gain orbital energy. This effect was dubbed "negative DF." We use a semianalytic model to study the impact of negative DF on pairs of MBHs in merger remnant galaxies evolving under the combined influence of stellar and gaseous DF. Our results show that for a wide range of merger galaxy and MBH properties negative DF reduces the MBH pairing probability by ∼46%. The suppression of MBH pairing is most severe in galaxies with one or more of these properties: (1) a gas fraction of fg ≥ 0.1; (2) a galactic gas disk rotating close to the circular velocity; (3) MBH pairs in prograde, low eccentricity orbits; and (4) MBH pairs with mass <108 M⊙. The last point is of importance because MBH pairs in this mass range are direct progenitors of merging binaries targeted by the future space-based gravitational wave observatory the Laser Interferometer Space Antenna (LISA).

Keywords: dynamical friction; gravitational interaction; galaxy dynamics; galaxy evolution; galaxy mergers; supermassive black holes
Insufficient Gas Accretion Caused the Decline in Cosmic Star-formation Activity Eight Billion Years Ago

Measurements of the atomic hydrogen (HI) properties of high-redshift galaxies are critical to understanding the decline in the star formation rate (SFR) density of the universe after its peak ≈8-11 Gyr ago. Here, we use ≈510 hr of observations with the upgraded Giant Metrewave Radio Telescope to measure the dependence of the average HI mass of star-forming galaxies at z = 0.74-1.45 on their average stellar mass and redshift by stacking their HI 21 cm emission signals. We divide our sample of 11,419 main-sequence galaxies at z = 0.74-1.45 into two stellar-mass (M *) subsamples, with M * > 1010 M ⊙ and M * < 1010 M ⊙, and obtain clear detections, at >4.6σ significance, of the stacked HI 21 cm emission in both subsamples. We find that galaxies with M * > 1010 M ⊙, which dominate the decline in the cosmic SFR density at z ≲ 1, have HI reservoirs that can sustain their SFRs for only a short period, 0.86 ± 0.20 Gyr, unless their HI is replenished via accretion. We also stack the HI 21 cm emission from galaxies in two redshift subsamples, at z = 0.74-1.25 and z = 1.25-1.45, again obtaining clear detections of the stacked HI 21 cm emission signals, at >5.2σ significance in both subsamples. We find that the average HI mass of galaxies with <M *> ≈ 1010 M ⊙ declines steeply over a period of ≈1 billion years, from (33.6 ± 6.4) × 109 M ⊙ at <z> ≈ 1.3 to (10.6 ± 1.9) × 109 M ⊙ at <z> ≈ 1.0, i.e., by a factor ≳3. We thus find direct evidence that accretion of HI onto star-forming galaxies at z ≈ 1 is insufficient to replenish their HI reservoirs and sustain their SFRs, thus resulting in the decline in the cosmic SFR density 8 billion years ago.

Keywords: galaxy evolution; radio spectroscopy; neutral hydrogen clouds
The Contribution of Small Impact Craters to Lunar Polar Wander

Changes in mass distribution affect the gravitational figure and reorient a planetary body's surface with respect to its rotational axis. The mass anomalies in the present-day lunar gravity field can reveal how the figure and pole position have evolved over the Moon's history. By examining sequentially each individual crater and basin, working backward in time order through the catalog of nearly 5200 craters and basins between 1200 and 20 km in diameter, we investigate their contribution to the lunar gravitational figure and reconstruct the evolution of the pole position by extracting their gravitational signatures from the present-day Moon. We find that craters and basins in this diameter range, which excludes South Pole-Aitken, have contributed to nearly 25% of the present-day power from the Moon's degree-2 gravitational figure and resulted in a total displacement of the Moon's pole by ~10° along the Earth-Moon tidal axis over the past ~4.25 billion years. This also implies that the geographical location of the Moon's rotational pole has not moved since ~3.8 Ga by more than ~2° in latitude owing to impacts, and this has implications for the long-term stability of volatiles in the polar regions.

Keywords: the moon; lunar evolution; lunar gravitational field; lunar geodesy; planetary polar regions; impact phenomena; lunar impacts; planetary structure; planetary dynamics
Star-Gas Misalignment in Galaxies. II. Origins Found from the Horizon-AGN Simulation

There have been many studies aiming to reveal the origins of the star-gas misalignment found in galaxies, but there still is a lack of understanding of the contribution from each formation channel candidate. We aim to answer the question by investigating the misaligned galaxies in the Horizon-AGN simulation. There are 27,903 galaxies of stellar mass M* > 1010M⊙ in our sample, of which 5984 are in a group in the halo mass of M200 > 1012M⊙. We have identified four main formation channels of misalignment and quantified their levels of contribution: mergers (35%), interaction with nearby galaxies (23%), interaction with dense environments or their central galaxies (21%), and secular evolution, including smooth accretion from neighboring filaments (21%). We found in the simulation that the gas, rather than stars, is typically more vulnerable to dynamical disturbances; hence, misalignment formation is mainly due to the change in the rotational axis of the gas rather than stars, regardless of the origin. We have also inspected the lifetime (duration) of the misalignment. The decay timescale of the misalignment shows a strong anticorrelation with the kinematic morphology (V/σ) and the cold gas fraction of the galaxy. The misalignment has a longer lifetime in denser regions, which is linked with the environmental impact on the host galaxy. There is a substantial difference in the length of the misalignment lifetime depending on the origin, and it can be explained by the magnitude of the initial position angle offset and the physical properties of the galaxies.

Keywords: galaxy evolution
Supermassive Black Holes with High Accretion Rates in Active Galactic Nuclei. XII. Reverberation Mapping Results for 15 PG Quasars from a Long-duration High-cadence Campaign

In this work, we present the first results of the long-term high-cadence spectroscopic monitoring of 15 PG quasars with relatively strong Fe ii emission, as a part of a broader reverberation mapping campaign performed using the Calar Alto Observatory's 2.2 m telescope. The V-band, 5100 Å continuum, and Hβ broad emission line light curves are measured for a set of quasars for periods ranging from dozens to more than a hundred epochs between 2017 May and 2020 July. Accurate time lags between the variations of the Hβ broad-line fluxes and the optical continuum strength are obtained for all 15 quasars, ranging from ${17.0}_{-3.2}^{+2.5}$?--> 17.0 - 3.2 + 2.5 to ${95.9}_{-23.9}^{+7.1}$?--> 95.9 - 23.9 + 7.1 days in the rest frame. The virial masses of the central supermassive black holes are derived for all 15 quasars, ranging between ${0.50}_{-0.19}^{+0.18}$?--> 0.50 - 0.19 + 0.18 and ${19.17}_{-2.73}^{+2.98}$?--> 19.17 - 2.73 + 2.98 in units of 107M⊙. For 11 of the objects in our sample, this is the first reverberation analysis to be published. Of the rest, two objects have been the subject of previous reverberation studies, but we determine time lags for these that are only half as long as those found in the earlier investigations, which had only been able to sample much more sparsely. The remaining two objects have previously been monitored with high sampling rates. Our results here are consistent with the earlier findings, in the sense that the time lag and the line width vary inversely, consistent with virialization.

Keywords: supermassive black holes; seyfert galaxies; active galactic nuclei; quasars; reverberation mapping; time domain astronomy
ALMA 300 pc Resolution Imaging of a z = 6.79 Quasar: No Evidence for Supermassive Black Hole Influence on the C II Kinematics

We present Atacama Large Millimeter/submillimeter Array (ALMA) [C II] 158 μm and dust continuum observations of the z = 6.79 quasar J0109-3047 at a resolution of 0.″045 (~300 pc). The dust and [C II] emission are enclosed within a ~500 pc radius, with the central beam (r < 144 pc) accounting for ~25% (8%) of the total continuum ([C II]) emission. The far-infrared (FIR) luminosity density increases radially from ~5 × 1011 L ⊙ kpc-2 to a central value of ~70 × 1011 L ⊙ kpc-2 (SFRD ~50-700 M ⊙yr-1 kpc-2). The [C II] kinematics are dispersion dominated with a constant velocity dispersion of 137 ± 6 km s-1. The constant dispersion implies that the underlying mass distribution is not centrally peaked, consistent with the expectations of a flat gas mass profile. The lack of an upturn in velocity dispersion within the central beam is inconsistent with a black hole mass greater than M BH < 6.5 × 108 M ⊙ (2σ level), unless highly fine-tuned changes in the interstellar medium properties conspire to produce a decrease of the gas mass in the central beam comparable to the black hole mass. Our observations therefore imply either that (a) the black hole is less massive than previously measured, or (b) the central peak of the FIR and [C II] emission are not tracing the location of the black hole, as suggested by the tentative offset between the near-infrared position of the quasar and the ALMA continuum emission.

Keywords: high-redshift galaxies; quasars; interstellar medium; submillimeter astronomy; supermassive black holes; galaxy dynamics
Structural and Dynamical Analysis of the Quiescent Molecular Ridge in the Large Magellanic Cloud

We present a comparison of low-J 13CO and CS observations of four different regions in the LMC-the quiescent Molecular Ridge, 30 Doradus, N159, and N113, all at a resolution of ~3 pc. The regions 30 Dor, N159, and N113 are actively forming massive stars, while the Molecular Ridge is forming almost no massive stars, despite its large reservoir of molecular gas and proximity to N159 and 30 Dor. We segment the emission from each region into hierarchical structures using dendrograms and analyze the sizes, masses, and line widths of these structures. We find that the Ridge has significantly lower kinetic energy at a given size scale and also lower surface densities than the other regions, resulting in higher virial parameters. This suggests that the Ridge is not forming massive stars as actively as the other regions because it has less dense gas and not because collapse is suppressed by excess kinetic energy. We also find that these physical conditions and energy balance vary significantly within the Ridge and that this variation appears only weakly correlated with distance from sites of massive-star formation such as R136 in 30 Dor, which is ~1 kpc away. These variations also show only a weak correlation with local star formation activity within the clouds.

Keywords: interstellar medium; large magellanic cloud; star formation; millimeter astronomy
Spectroscopic Orbits of Subsystems in Multiple Stars. IX

New spectroscopic orbits of inner subsystems in 14 hierarchies are determined from long-term monitoring with the optical echelle spectrometer, CHIRON. Their main components are nearby solar-type stars belonging to nine triple systems (HIP 3645, 14307, 36165, 79980, 103735, 103814, 104440, 105879, 109443) and five quadruples of 2 + 2 hierarchy (HIP 41171, 49336, 75663, 78163, and 117666). The inner periods range from 254 days to 18 yr. Inner subsystems in HIP 3645, 14313, 79979, 103735, 104440, and 105879 are resolved by speckle interferometry, and their combined spectro-interferometric orbits are derived here. Astrometric orbits of HIP 49336 Aa,Ab and HIP 117666 Aa,Ab are determined from wobble in the observed motion of the outer pairs. Comparison with three spectroscopic orbits found in the Gaia data release 3 archive reveals that Gaia underestimated the amplitudes (except for HIP 109443), while the periods match approximately. This work contributes new data on the architecture of nearby hierarchical systems, complementing their statistics.

Keywords: multiple stars; visual binary stars; spectroscopic binary stars
Low-frequency Radio Recombination Lines Away from the Inner Galactic Plane

Diffuse radio recombination lines (RRLs) in the Galaxy are possible foregrounds for redshifted 21 cm experiments. We use EDGES drift scans centered at -26.°7 decl. to characterize diffuse RRLs across the southern sky. We find that RRLs averaged over the large antenna beam (72° × 110°) reach minimum amplitudes of R.A. = 2-6 hr. In this region, the Cα absorption amplitude is 33 ± 11 mK (1σ) averaged over 50-87 MHz (27 ≳ z ≳ 15 for the 21 cm line) and increases strongly as frequency decreases. Cβ and Hα lines are consistent with no detection with amplitudes of 13 ± 14 and 12 ± 10 mK (1σ), respectively. At 108-124.5 MHz (z ≈ 11) in the same region, we find no evidence for carbon or hydrogen lines at the noise level of 3.4 mK (1σ). Conservatively assuming that observed lines come broadly from the diffuse interstellar medium, as opposed to a few compact regions, these amplitudes provide upper limits on the intrinsic diffuse lines. The observations support expectations that Galactic RRLs can be neglected as significant foregrounds for a large region of sky until redshifted 21 cm experiments, particularly those targeting cosmic dawn, move beyond the detection phase. We fit models of the spectral dependence of the lines averaged over the large beam of EDGES, which may contain multiple line sources with possible line blending, and find that including degrees of freedom for expected smooth, frequency-dependent deviations from local thermodynamic equilibrium (LTE) is preferred over simple LTE assumptions for Cα and Hα lines. For Cα we estimate departure coefficients 0.79 < b n β n < 4.5 along the inner Galactic plane and 0 < b n β n < 2.3 away from the inner Galactic plane.

Keywords: radio spectroscopy; interstellar medium; milky way galaxy; reionization
Bayesian Analysis for Remote Biosignature Identification on exoEarths (BARBIE). II. Using Grid-based Nested Sampling in Coronagraphy Observation Simulations for O2 and O3

We present the results for the detectability of the O2 and O3 molecular species in the atmosphere of an Earth-like planet using reflected light at visible wavelengths. By quantifying the detectability as a function of the signal-to-noise ratio (S/N), we can constrain the best methods to detect these biosignatures with next-generation telescopes designed for high-contrast coronagraphy. Using 25 bandpasses between 0.515 and 1 μm and a preconstructed grid of geometric albedo spectra, we examined the spectral sensitivity needed to detect these species for a range of molecular abundances. We first replicate a modern-Earth twin atmosphere to study the detectability of current O2 and O3 levels, and then expand to a wider range of literature-driven abundances for each molecule. We constrain the optimal 20%, 30%, and 40% bandpasses based on the effective S/N of the data, and define the requirements for the possibility of simultaneous molecular detection. We present our findings of O2 and O3 detectability as functions of the S/N, wavelength, and abundance, and discuss how to use these results for optimizing future instrument designs. We find that O2 is detectable between 0.64 and 0.83 μm with moderate-S/N data for abundances near that of modern Earth and greater, but undetectable for lower abundances consistent with a Proterozoic Earth. O3 is detectable only at very high S/N data in the case of modern-Earth abundances; however, it is detectable at low-S/N data for higher O3 abundances that can occur from efficient abiotic O3 production mechanisms.

Keywords: exoplanets; exoplanet atmospheres; bayesian statistics
Improved Fe II Emission-line Models for AGNs Using New Atomic Data Sets

Understanding the Fe II emission from active galactic nuclei (AGNs) has been a grand challenge for many decades. The rewards from understanding the AGN spectra would be immense, involving both quasar classification schemes such as "Eigenvector 1" and tracing the chemical evolution of the cosmos. Recently, three large Fe II atomic data sets with radiative and electron collisional rates have become available. We have incorporated these into the spectral synthesis code CLOUDY and examined predictions using a new generation of AGN spectral energy distribution (SED), which indicates that the ultraviolet (UV) emission can be quite different depending on the data set utilized. The Smyth et al. data set better reproduces the observed Fe II template of the I ZW 1 Seyfert galaxy in the UV and optical regions, and we adopt these data. We consider both thermal and microturbulent clouds and show that a microturbulence of ≈100 km s-1 reproduces the observed shape and strength of the so-called Fe II "UV bump." Comparing our predictions to the observed Fe II template, we derive a typical cloud density of 1011 cm-3 and photon flux of 1020 cm-2 s-1, and show that these largely reproduce the observed Fe II emission in the UV and optical. We calculate the I(Fe II)/I(Mg II) emission-line intensity ratio using our best-fitting model and obtain log(I(Fe II)/I(Mg II)) ∼ 0.7, suggesting many AGNs have a roughly solar Fe/Mg abundance ratio. Finally, we vary the Eddington ratio and SED shape as a step in understanding the Eigenvector 1 correlation.

Keywords: atomic physics; ionization; photoionization; active galactic nuclei; quasars; seyfert galaxies
The First Short GRB Millimeter Afterglow: The Wide-angled Jet of the Extremely Energetic SGRB 211106A

We present the discovery of the first millimeter afterglow of a short-duration γ-ray burst (SGRB) and the first confirmed afterglow of an SGRB localized by the GUANO system on Swift. Our Atacama Large Millimeter/Sub-millimeter Array (ALMA) detection of SGRB 211106A establishes an origin in a faint host galaxy detected in Hubble Space Telescope imaging at 0.7 ≲ z ≲ 1.4. From the lack of a detectable optical afterglow, coupled with the bright millimeter counterpart, we infer a high extinction, A V ≳ 2.6 mag along the line of sight, making this one of the most highly dust-extincted SGRBs known to date. The millimeter-band light curve captures the passage of the synchrotron peak from the afterglow forward shock and reveals a jet break at {t}_{\mathrm{jet}}={29.2}_{-4.0}^{+4.5}$ days. For a presumed redshift of z = 1, we infer an opening angle, θ jet = (15.°5 ± 1.°4), and beaming-corrected kinetic energy of \mathrm{log}({E}_{{\rm{K}}}/\mathrm{erg})=51.8\pm 0.3$ , making this one of the widest and most energetic SGRB jets known to date. Combining all published millimeter-band upper limits in conjunction with the energetics for a large sample of SGRBs, we find that energetic outflows in high-density environments are more likely to have detectable millimeter counterparts. Concerted afterglow searches with ALMA should yield detection fractions of 24%-40% on timescales of ≳2 days at rates of ≈0.8-1.6 per year, outpacing the historical discovery rate of SGRB centimeter-band afterglows.

Keywords: gamma-ray bursts; astronomy data modeling; radio astronomy; millimeter astronomy; time domain astronomy; relativistic jets; high energy astrophysics
Statistical Analysis of the Distribution and Evolution of Mirror Structures in the Martian Magnetosheath

The mirror-mode structures in the Martian magnetosheath that were observed by Mars Atmosphere and Volatile Evolution during 2015-2018 are analyzed statistically. It is found that most mirror-mode events occurred close to the bow shock. Morphological categorization based on skewness of the magnetic field shows that ~46.57% of the observed mirror-mode events are peak-like, ~40.25% are wave-like, and ~13.18% are dip-like. The mirror-mode structures mostly saturate in a very short time after their formation near the bow shock, which is a result of the high temperature anisotropy and high plasma beta at this location. Carried downstream by the magnetosheath flow, the mirror-mode structures remain in nonlinear saturation states. Meanwhile, the dayside magnetosheath plasma largely deviates from marginal stability, which is a state commonly that is expected in the terrestrial magnetosheath. By flowline tracing in an MHD model, it is found the mirror structures can be divided into two groups: ~80% of the events that are observed near the bow shock evolve less than 10 s in plasma with high temperature anisotropy and high plasma beta value, keeping in saturated states; the other 20% of the events evolve following a similar process to that at the Earth, undergoing morphology transition in response to the local plasma conditions. However, the dayside magnetosheath is largely in an unstable condition, which prevents the mirror-mode structures from fully evolving into the decaying phase. Our results suggest that energy dispassion through wave-particle interaction might not be sufficient to remove the free energy that is introduced by the solar wind-Mars interaction.

Keywords: planetary magnetospheres; mars; space plasmas
Chemical Differentiation around Five Massive Protostars Revealed by ALMA: Carbon-chain Species and Oxygen/Nitrogen-bearing Complex Organic Molecules

We present Atacama Large Millimeter/submillimeter Array Band 3 data toward five massive young stellar objects (MYSOs), and investigate relationships between unsaturated carbon-chain species and saturated complex organic molecules (COMs). An HC5N (J = 35-34) line has been detected from three MYSOs, where nitrogen (N)-bearing COMs (CH2CHCN and CH3CH2CN) have been detected. The HC5N spatial distributions show compact features and match with a methanol (CH3OH) line with an upper-state energy around 300 K, which should trace hot cores. The hot regions are more extended around the MYSOs where N-bearing COMs and HC5N have been detected compared to two MYSOs without these molecular lines, while there are no clear differences in the bolometric luminosity and temperature. We run chemical simulations of hot-core models with a warm-up stage, and compare with the observational results. The observed abundances of HC5N and COMs show good agreements with the model at the hot-core stage with temperatures above 160 K. These results indicate that carbon-chain chemistry around the MYSOs cannot be reproduced by warm carbon-chain chemistry, and a new type of carbon-chain chemistry occurs in hot regions around MYSOs.

Keywords: astrochemistry; interstellar molecules; massive stars; star formation