adsabs/SciX_UAT_keywords huggingface dataset:
Reconstruction of Cosmological Initial Density Field with Observations from the Epoch of Reionization

The initial density distribution provides a basis for understanding the complete evolution of cosmological density fluctuations. While reconstruction in our local Universe exploits the observations of galaxy surveys with large volumes, observations of high-redshift galaxies are performed with a small field of view and therefore can hardly be used for reconstruction. Here, we propose reconstructing the initial density field using the H I 21 cm and CO line intensity maps from the epoch of reionization. Observations of these two intensity maps provide complementary information on the density field—the H I 21 cm field is a proxy of matter distributions in the neutral regions, while the CO line intensity maps are sensitive to the high-density, star-forming regions that host the sources for reionization. Technically, we employ the conjugate gradient method and develop the machinery for minimizing the cost function for the intensity mapping observations. Analytical expressions for the gradient of cost function are derived explicitly. We show that the resimulated intensity maps match the input maps of mock observations using semi-numerical simulations of reionization with an rms error ≲7% at all stages of reionization. This reconstruction is also robust with an rms error of ∼10% when an optimistic level of shot noise is applied to the CO map or white noise at the level of ≲10% of the standard deviation is applied to each map. Our proof-of-concept work demonstrates the robustness of the reconstruction method, thereby providing an effective technique for reconstructing the cosmological initial density distribution from high-redshift observations.

Keywords: reionization; h i line emission; co line emission; initial conditions of the universe; line intensities
Orbital Support and Evolution of Flat Profiles of Bars (Shoulders)

Many barred galaxies exhibit upturns (shoulders) in their bar-major-axis density profile. Simulation studies have suggested that shoulders are supported by looped x 1 orbits, occur in growing bars, and can appear after bar buckling. We investigate the orbital support and evolution of shoulders via frequency analyses of orbits in simulations. We confirm that looped orbits are shoulder-supporting, and can remain so, to a lesser extent, after being vertically thickened. We show that looped orbits appear at the resonance ( Ω φ - ΩP)/Ω R = 1/2 (analogous to the classical inner Lindblad resonance, and here called ILR) with vertical-to-radial frequency ratios 1 ≲ Ω z /Ω R ≲ 3/2 (vertically warm orbits). Cool orbits at the ILR (those with Ω z /Ω R > 3/2) are vertically thin and have no loops, contributing negligibly to shoulders. As bars slow and thicken, either secularly or by buckling, they populate warm orbits at the ILR. Further thickening carries these orbits toward crossing the vertical ILR [vILR, ( Ω φ - ΩP)/Ω z = 1/2], where they convert in-plane motion to vertical motion, become chaotic, kinematically hotter, and less shoulder-supporting. Hence, persistent shoulders require bars to trap new stars, consistent with the need for a growing bar. Since buckling speeds up trapping on warm orbits at the ILR, it can be followed by shoulder formation, as seen in simulations. This sequence supports the recent observational finding that shoulders likely precede the emergence of BP-bulges. The python module for the frequency analysis, naif, is made available.

Keywords: galactic bar; galaxy dynamics; orbits; galaxy bars; n-body simulations
Photodissociation Rate, Excess Energy, and Kinetic Total Energy Release for the Photolysis of H2O Producing O(1S) by Solar UV Radiation Field

Forbidden atomic oxygen lines in emission are ubiquitous for cometary spectra in the visible region, and the oxygen atoms in metastable states causing the forbidden emission lines are considered as a proxy of H2O in coma. However, the photodissociation rate and related quantities for the dissociation reaction producing O(1S) from H2O have never been estimated based on experimental studies. Based on the recent laboratory study of the photodissociation reaction of H2O producing O(1S) by Chang et al., we derived the photodissociation rates of the reactions for both the O(1S) and O(1D) channels, consistent with the green-to-red line ratios observed in comets so far. Furthermore, the total kinetic energies released for the photodissociation products are also consistent with the intrinsic line widths of forbidden atomic oxygen emission lines observed in comets. The photodissociation rates of H2O leading to O(1S) and O(1D) calculated here do not significantly change the previous estimates of CO2/H2O in comets based on the green-to-red line ratios of the comets if we use the photodissociation rates of CO2 (calculated elsewhere) with a correction for the difference of solar UV spectra used for calculating photodissociation rates of H2O and CO2.

Keywords: molecular physics
Applying the Metallicity-dependent Binary Fraction to Double White Dwarf Formation: Implications for LISA

Short-period double white dwarf (DWD) binaries will be the most prolific source of gravitational waves (GWs) for the Laser Interferometer Space Antenna (LISA). DWDs with GW frequencies below ~1 mHz will be the dominant contributor to a stochastic foreground caused by overlapping GW signals. Population modeling of Galactic DWDs typically assumes a binary fraction of 50% and a log-uniform zero-age main sequence (ZAMS) orbital period distribution. However, recent observations have shown that the binary fraction of close, solar-type stars exhibits a strong anticorrelation with metallicity that modulates the ZAMS orbital period distribution below 104 days. In this study, we perform the first simulation of the Galactic DWD population observable by LISA that incorporates an empirically derived metallicity-dependent binary fraction, using the binary population synthesis suite COSMIC and a metallicity-dependent star formation history. We compare two models: one that assumes a metallicity-dependent binary fraction, and one with a binary fraction of 50%. We repeat our analysis for three different assumptions for Roche-lobe overflow interactions. We find that while metallicity impacts the evolution and intrinsic properties of our simulated DWD progenitor binaries, the LISA-resolvable populations of the two models remain roughly indistinguishable. However, the size of the total Galactic DWD population orbiting in the LISA frequency band is reduced by more than half when accounting for a metallicity-dependent binary fraction for two of our four variations, which also lowers the effective foreground. The LISA population remains unchanged in number for two variations, highlighting the sensitivity of the population to binary evolution prescriptions.

Keywords: gravitational wave sources; white dwarf stars; close binary stars; stellar evolution
Hα Emission and H II Regions at the Locations of Recent Supernovae in Nearby Galaxies

We present a statistical analysis of the local, ≈50–100 pc scale, Hα emission at the locations of recent (≤125 yr) supernovae (SNe) in nearby star-forming galaxies. Our sample consists of 32 SNe in 10 galaxies that are targets of the PHANGS-MUSE survey. We find that 41% (13/32) of these SNe occur coincident with a previously identified H II region. For comparison, H II regions cover 32% of the area within ±1 kpc of any recent SN. Contrasting this local covering fraction with the fraction of SNe coincident with H II regions, we find a statistical excess of 7.6% ± 8.7% of all SNe to be associated with H II regions. This increases to an excess of 19.2% ± 10.4% when considering only core-collapse SNe (CCSNe). These estimates appear to be in good agreement with qualitative results from new, higher-resolution Hubble Space Telescope Hα imaging, which also suggests many CCSNe detonate near but not in H II regions. Our results appear consistent with the expectation that only a modest fraction of stars explode during the first ≲5 Myr of the life of a stellar population when Hα emission is expected to be bright. Of the H II region associated SNe, 85% (11/13) also have associated detected CO (2–1) emission, indicating the presence of molecular gas. The SNe associated with H II regions have typical extinctions of A V ∼ 1 mag, consistent with a significant amount of pre-clearing of gas from the region before the SNe explode.

Keywords: supernovae; core-collapse supernovae; h ii regions; star forming regions; stellar feedback; galaxy evolution
Day–Night Transport-induced Chemistry and Clouds on WASP-39b: Gas-phase Composition

JWST has recently detected the first robust photochemical product on an exoplanet: sulfur dioxide (SO2) on WASP-39b. The data from the NIRISS instrument also reveal signs of partial coverage of clouds. Most of the previous studies have focused on interpreting spectral data with 1D models. To explore how the chemical species and cloud particles are altered by global circulation, we applied a 2D photochemical model and a 2D microphysical cloud model separately to postprocess the thermal and dynamical structures simulated by a 3D general circulation model of WASP-39b. We found that SO2 produced by photochemistry on the dayside can be transported to the nightside owing to the efficient replenishment of horizontal transport. The morning–evening limb differences in methane (CH4) abundances predicted by the 1D models disappeared after horizontal transport is included. Similarly, the inclusion of horizontal transport also reduced the limb differences in SO2. Our modeling results suggest that the fast zonal wind results in minimal or negligible limb asymmetry in composition. Based on the synthetic spectra generated by our 2D atmosphere simulations, we propose that observing SO2 absorption in the emission spectra of WASP-39b at different phases may offer opportunities to probe the horizontal quenching process of photochemical products. We will focus on the gas-phase chemistry in this paper and leave the results regarding clouds in the subsequent paper as part of the series.

Keywords: exoplanet atmospheres; exoplanet atmospheric composition; extrasolar gaseous planets
The First Integral Field Unit Spectroscopic View of Shocked Cluster Galaxies

Galaxy clusters grow by merging with other clusters, giving rise to Mpc-wide shock waves that travel at 1000-2500 km s-1 through the intracluster medium. To study the effects of merger shocks on the properties of cluster galaxies, we present the first spatially resolved spectroscopic view of five Hα-emitting galaxies located in the wake of shock fronts in the low redshift (z ∼ 0.2), massive (∼2 × 1015M⊙), post-core passage merging cluster, CIZA J2242.8+5301 (nicknamed the "Sausage"). Our Gemini/Gemini Multi-Object Spectrograph-North integral field unit (IFU) observations, designed to capture Hα and [N II] emission, reveal the nebular gas distribution, kinematics, and metallicities in the galaxies over >16 kpc scales. While the galaxies show evidence for rotational support, the flux and velocity maps have complex features like tails and gas outflows aligned with the merger axis of the cluster. With gradients that are incompatible with inside-out disk growth, the metallicity maps are consistent with sustained star formation (SF) throughout and outside of the galactic disks. In combination with previous results, these pilot observations provide further evidence of a likely connection between cluster mergers and SF triggering in cluster galaxies, a potentially fundamental discovery revealing the interaction of galaxies with their environment.

Keywords: emission line galaxies; galaxy evolution; galaxy clusters; metallicity; star formation; shocks
Interpretable Machine Learning for Finding Intermediate-mass Black Holes

Definitive evidence that globular clusters (GCs) host intermediate-mass black holes (IMBHs) is elusive. Machine-learning (ML) models trained on GC simulations can in principle predict IMBH host candidates based on observable features. This approach has two limitations: first, an accurate ML model is expected to be a black box due to complexity; second, despite our efforts to simulate GCs realistically, the simulation physics or initial conditions may fail to reflect reality fully. Therefore our training data may be biased, leading to a failure in generalization to observational data. Both the first issue—explainability/interpretability—and the second—out of distribution generalization and fairness—are active areas of research in ML. Here we employ techniques from these fields to address them: we use the anchors method to explain an Extreme Gradient Boosting (XGBoost) classifier; we also independently train a natively interpretable model using Certifiably Optimal RulE ListS (CORELS). The resulting model has a clear physical meaning, but loses some performance with respect to XGBoost. We evaluate potential candidates in real data based not only on classifier predictions but also on their similarity to the training data, measured by the likelihood of a kernel density estimation model. This measures the realism of our simulated data and mitigates the risk that our models may produce biased predictions by working in extrapolation. We apply our classifiers to real GCs, obtaining a predicted classification, a measure of the confidence of the prediction, an out-of-distribution flag, a local rule explaining the prediction of XGBoost, and a global rule from CORELS.

Keywords: astrophysical black holes; intermediate-mass black holes
Waltzing Binaries: Probing the Line-of-sight Acceleration of Merging Compact Objects with Gravitational Waves

The line-of-sight acceleration of a compact binary coalescence (CBC) event would modulate the shape of the gravitational waves (GWs) it produces with respect to the corresponding nonaccelerated CBC. Such modulations could be indicative of its astrophysical environment. We investigate the prospects of detecting this acceleration in future observing runs of the LIGO-Virgo-KAGRA network, as well as in next-generation (XG) detectors and the proposed DECIGO. We place the first observational constraints on this acceleration for putative binary neutron star mergers GW170817 and GW190425. We find no evidence of line-of-sight acceleration in these events at 90% confidence. Prospective constraints for the fifth observing run of the LIGO at A+ sensitivity suggest that accelerations for typical binary neutron stars (BNSs) could be constrained with a precision of a/c ~ 10-7 [s-1], assuming a signal-to-noise ratio of 10. These improve to a/c ~ 10-9 [s-1] in XG detectors, and a/c ~ 10-16 [s-1] in DECIGO. We also interpret these constraints in the context of mergers around supermassive black holes.

Keywords: gravitational wave sources
SOFIA/FORCAST Observations of R Aqr: Monitoring the Dust Emission

We present mid-infrared spectra of the symbiotic Mira, R Aqr obtained with the Faint Object infraRed CAmera instrument on the Stratospheric Observatory for Infrared Astronomy in 2016 and 2017. These data, supplemented with Infrared Space Observatory observations from 20 yr earlier, allow us to study the variation of the silicate dust emission over short and long timescales. Radiative transfer models for the dust emission from the circumstellar shell indicate that changes that occur within a pulsation period are driven mainly by the variation properties of the asymptotic giant branch star, and do not require any change in the grain composition. The models show that the longer-term changes are due to variations in the dust density, probably modulated by the orbital separation of the binary companion stars. The models also suggest the presence of micron-size dust grains at all epochs.

Keywords: asymptotic giant branch; symbiotic binary stars; circumstellar dust; stellar pulsations
The TESS Grand Unified Hot Jupiter Survey. II. Twenty New Giant Planets

NASA's Transiting Exoplanet Survey Satellite (TESS) mission promises to improve our understanding of hot Jupiters by providing an all-sky, magnitude-limited sample of transiting hot Jupiters suitable for population studies. Assembling such a sample requires confirming hundreds of planet candidates with additional follow-up observations. Here we present 20 hot Jupiters that were detected using TESS data and confirmed to be planets through photometric, spectroscopic, and imaging observations coordinated by the TESS Follow-up Observing Program. These 20 planets have orbital periods shorter than 7 days and orbit relatively bright FGK stars (10.9 < G < 13.0). Most of the planets are comparable in mass to Jupiter, although there are four planets with masses less than that of Saturn. TOI-3976b, the longest-period planet in our sample (P = 6.6 days), may be on a moderately eccentric orbit (e = 0.18 ± 0.06), while observations of the other targets are consistent with them being on circular orbits. We measured the projected stellar obliquity of TOI-1937A b, a hot Jupiter on a 22.4 hr orbit with the Rossiter-McLaughlin effect, finding the planet's orbit to be well aligned with the stellar spin axis (∣λ∣ = 4.°0 ± 3.°5). We also investigated the possibility that TOI-1937 is a member of the NGC 2516 open cluster but ultimately found the evidence for cluster membership to be ambiguous. These objects are part of a larger effort to build a complete sample of hot Jupiters to be used for future demographic and detailed characterization work. *This paper includes data gathered with the 6.5 m Magellan Telescopes located at Las Campanas Observatory, Chile

Keywords: exoplanets; hot jupiters; radial velocity; exoplanet detection methods; transit photometry
COMAP Early Science. VIII. A Joint Stacking Analysis with eBOSS Quasars

We present a new upper limit on the cosmic molecular gas density at z = 2.4–3.4 obtained using the first year of observations from the CO Mapping Array Project (COMAP). COMAP data cubes are stacked on the 3D positions of 243 quasars selected from the Extended Baryon Oscillation Spectroscopic Survey (eBOSS) catalog, yielding a 95% upper limit for flux from CO(1–0) line emission of 0.129 Jy km s‑1. Depending on the balance of the emission between the quasar host and its environment, this value can be interpreted as an average CO line luminosity ${L}_{\mathrm{CO}}^{{\prime} }$ of eBOSS quasars of ≤1.26 × 1011 K km pc2 s‑1, or an average molecular gas density ${\rho }_{{{\rm{H}}}_{2}}$ in regions of the Universe containing a quasar of ≤1.52 × 108 M ⊙ cMpc‑3. The ${L}_{\mathrm{CO}}^{{\prime} }$ upper limit falls among CO line luminosities obtained from individually targeted quasars in the COMAP redshift range, and the ${\rho }_{{{\rm{H}}}_{2}}$ value is comparable to upper limits obtained from other line intensity mapping (LIM) surveys and their joint analyses. Further, we forecast the values obtainable with the COMAP/eBOSS stack after the full 5 yr COMAP Pathfinder survey. We predict that a detection is probable with this method, depending on the CO properties of the quasar sample. Based on the achieved sensitivity, we believe that this technique of stacking LIM data on the positions of traditional galaxy or quasar catalogs is extremely promising, both as a technique for investigating large galaxy catalogs efficiently at high redshift and as a technique for bolstering the sensitivity of LIM experiments, even with a fraction of their total expected survey data.

Keywords: co line emission; cosmological evolution; high-redshift galaxies; molecular gas; quasars; radio astronomy
The Gemini Planet Imager Exoplanet Survey: Dynamical Mass of the Exoplanet β Pictoris b from Combined Direct Imaging and Astrometry

We present new observations of the planet β Pictoris b from 2018 with the Gemini Planet Imager (GPI), the first GPI observations following conjunction. Based on these new measurements, we perform a joint orbit fit to the available relative astrometry from ground-based imaging, the Hipparcos Intermediate Astrometric Data (IAD), and the Gaia DR2 position, and demonstrate how to incorporate the IAD into direct imaging orbit fits. We find a mass consistent with predictions of hot-start evolutionary models and previous works following similar methods, though with larger uncertainties: 12.8+5.3-3.2 MJup. Our eccentricity determination of ${0.12}_{-0.03}^{+0.04}$ disfavors circular orbits. We consider orbit fits to several different imaging data sets, and find generally similar posteriors on the mass for each combination of imaging data. Our analysis underscores the importance of performing joint fits to the absolute and relative astrometry simultaneously, given the strong covariance between orbital elements. Time of conjunction is well-constrained within 2.8 days of 2017 September 13, with the star behind the planet's Hill sphere between 2017 April 11 and 2018 February 16 (±18 days). Following the recent radial velocity detection of a second planet in the system, β Pic c, we perform additional two-planet fits combining relative astrometry, absolute astrometry, and stellar radial velocities. These joint fits find a significantly smaller mass (8.0 ± 2.6 MJup) for the imaged planet β Pic b, in a somewhat more circular orbit. We expect future ground-based observations to further constrain the visual orbit and mass of the planet in advance of the release of Gaia DR4.

Keywords: astrometry; direct imaging; exoplanets; coronagraphic imaging; orbit determination
An Ab Initio Approach to Antiproton Modulation in the Inner Heliosphere

Recent advances in the detection of cosmic-ray (CR) antiproton intensities at Earth have the potential to provide valuable new insights in the search for dark matter. As such, a fuller understanding of the modulation of these particles due to the influence of the Sun is of vital importance. Valuable insights can be gained through the study of galactic CR protons, as the transport parameters for these particles are theoretically expected to be the same as those for antiprotons, barring drift effects. As such, the present study develops a data-driven, 3D time-dependent ab initio model for the modulation of galactic CR protons in the region of the heliosphere dominated by the supersonic solar wind, which yields results in good agreement with spacecraft observations over several solar cycles when an observationally motivated expression for the differential intensity spectrum of these particles at the heliospheric termination shock is employed. This model is then applied to the study of solar-cycle-dependent antiproton modulation using two current estimates for the local interstellar differential intensities of these particles. This approach yields estimates of antiproton intensities at the heliospheric termination shock that are considerably lower than the proposed interstellar spectra, with the implication that a significant amount of antiproton modulation is expected to occur in the heliosheath.

Keywords: galactic cosmic rays; solar cycle; heliosphere
A Chemo-dynamical Link between the Gjöll Stream and NGC 3201

Recent analysis of the second data release of Gaia has revealed a number of new stellar streams surrounding the Milky Way. It has been suggested that one of these streams, Gjöll, is associated with the globular cluster NGC 3201, but thus far the association has only been based on kinematics of the stream stars. In this work we identify five likely stream members in the Gaia data that are bright enough for high-resolution spectroscopic follow-up with the Harlan J. Smith telescope at McDonald Observatory. One star is ruled out as a member based on its radial velocity. Abundance analysis of the remaining four kinematic members reveals a good chemical match to NGC 3201 for two of the stars, driven by their similar Al and α-element abundances. Of the remaining two, one shows no chemical similarity to NGC 3201 and is likely an unassociated Milky Way halo field star, while the other exhibits a similar Al abundance but has somewhat lower α-element abundances. The chemical tagging of stars in the Gjöll stream to NGC 3201 confirms this association and provides direct proof of the hierarchical formation of the Milky Way.

Keywords: milky way dynamics; chemical abundances; globular star clusters