adsabs/SciX_UAT_keywords huggingface dataset:
Measuring Cosmological Parameters with Type Ia Supernovae in redMaGiC Galaxies

Current and future cosmological analyses with Type Ia supernovae (SNe Ia) face three critical challenges: (i) measuring the redshifts from the SNe or their host galaxies; (ii) classifying the SNe without spectra; and (iii) accounting for correlations between the properties of SNe Ia and their host galaxies. We present here a novel approach that addresses each of these challenges. In the context of the Dark Energy Survey (DES), we analyze an SN Ia sample with host galaxies in the redMaGiC galaxy catalog, a selection of luminous red galaxies. redMaGiC photo-z estimates are expected to be accurate to σ Δz/(1+z) ~ 0.02. The DES-5YR photometrically classified SN Ia sample contains approximately 1600 SNe, and 125 of these SNe are in redMaGiC galaxies. We demonstrate that redMaGiC galaxies almost exclusively host SNe Ia, reducing concerns relating to classification uncertainties. With this subsample, we find similar Hubble scatter (to within ~0.01 mag) using photometric redshifts in place of spectroscopic redshifts. With detailed simulations, we show that the bias due to using redMaGiC photo-zs on the measurement of the dark energy equation of state w is up to Δw ~ 0.01-0.02. With real data, we measure a difference in w when using the redMaGiC photo-zs versus the spec-zs of Δw = 0.005. Finally, we discuss how SNe in redMaGiC galaxies appear to comprise a more standardizable population, due to a weaker relation between color and luminosity (β) compared to the DES-3YR population by ~5σ. These results establish the feasibility of performing redMaGiC SN cosmology with photometric survey data in the absence of spectroscopic data.

Keywords: cosmology; type ia supernovae
A Parameterized Model for Differential Galaxy Counts at Any Wavelength

Certain astronomy problems, such as the probabilistic cross-matching algorithms of Wilson & Naylor, require descriptions of galaxy counts as a function of brightness in many different filter sets, for which we often lack dedicated observations. With this motivation in mind, I present a simple model for calculating differential galaxy counts for an arbitrary bandpass or wavelength. The model uses a double Schechter function to describe the number density of galaxies as a function of absolute magnitude, including redshift-driven galaxy evolution, for both "blue" and "red" galaxy types. Collating previously derived values for the parameterization of the evolving Schechter function- ${M}_{0}^{* }$ , ${\phi }_{0}^{* }$ , P, Q, and α-I fit the dependencies of these parameters as a function of wavelength, allowing for the tabulation of differential galaxy counts in a new filter for which observations are unavailable. Finally, I briefly compare the model with some differential galaxy counts obtained from the literature.

Keywords: galaxy counts; galaxy luminosities; galaxy photometry
A Model Earth-sized Planet in the Habitable Zone of α Centauri A/B

The bulk chemical composition and interior structure of rocky exoplanets are fundamentally important to understand their long-term evolution and potential habitability. Observations of the chemical compositions of solar system rocky bodies and of other planetary systems have increasingly shown a concordant picture that the chemical composition of rocky planets reflects that of their host stars for refractory elements, whereas this expression breaks down for volatiles. This behavior is explained by devolatilization during planetary formation and early evolution. Here we apply a devolatilization model calibrated with solar system bodies to the chemical composition of our nearest Sun-like stars-α Centauri A and B-to estimate the bulk composition of any habitable-zone rocky planet in this binary system ("α-Cen-Earth"). Through further modeling of likely planetary interiors and early atmospheres, we find that, compared to Earth, such a planet is expected to have (i) a reduced (primitive) mantle that is similarly dominated by silicates, albeit enriched in carbon-bearing species (graphite/diamond); (ii) a slightly larger iron core, with a core mass fraction of ${38.4}_{-5.1}^{+4.7}$ wt% (see Earth's 32.5 ± 0.3 wt%); (iii) an equivalent water-storage capacity; and (iv) a CO2-CH4-H2O-dominated early atmosphere that resembles that of Archean Earth. Further taking into account its ~25% lower intrinsic radiogenic heating from long-lived radionuclides, an ancient α-Cen-Earth (~1.5-2.5 Gyr older than Earth) is expected to have less efficient mantle convection and planetary resurfacing, with a potentially prolonged history of stagnant-lid regimes.

Keywords: planetary interior; theoretical models; extrasolar rocky planets; atmospheric composition; exoplanet dynamics
RELICS: Properties of z ≥ 5.5 Galaxies Inferred from Spitzer and Hubble Imaging, Including A Candidate z ∼ 6.8 Strong [O III] emitter

We present constraints on the physical properties (including stellar mass, age, and star formation rate) of 207 6 ≲ z ≲ 8 galaxy candidates from the Reionization Lensing Cluster Survey (RELICS) and Spitzer-RELICS surveys. We measure photometry using T-PHOT and perform spectral energy distribution fitting using EAzY and BAGPIPES. Of the 207 candidates for which we could successfully measure (or place limits on) Spitzer fluxes, 23 were demoted to likely z < 4. Among the high-z candidates, we find intrinsic stellar masses between 1 × 106M⊙ and 4 × 109M⊙, and rest-frame UV absolute magnitudes between -22.6 and -14.5 mag. While our sample is mostly comprised of ${L}_{m\mathrm{UV}}/{L}_{m\mathrm{UV}}^{* }\lt 1$ <!-- --> galaxies, it extends to ${L}_{m\mathrm{UV}}/{L}_{m\mathrm{UV}}^{* }\sim 2$ <!-- --> . Our sample spans ∼4 orders of magnitude in stellar mass and star formation rates, and exhibits ages that range from maximally young to maximally old. We highlight 11 z ≥ 6.5 galaxies with detections in Spitzer/IRAC imaging, several of which show evidence for some combination of evolved stellar populations, large contributions of nebular emission lines, and/or dust. Among these is PLCKG287+32-2013, one of the brightest z ∼ 7 candidates known (AB mag 24.9 at 1.6 μm) with a Spitzer 3.6 μm flux excess suggesting strong [O III] + H-β emission (∼1000 Å rest-frame equivalent width). We discuss the possible uses and limits of our sample and present a public catalog of Hubble + Spitzer photometry along with physical property estimates for all objects in the sample. Because of their apparent brightnesses, high redshifts, and variety of stellar populations, these objects are excellent targets for follow-up with the James Webb Space Telescope.

Keywords: high-redshift galaxies; galaxies
Constraining Mornings and Evenings on Distant Worlds: A new Semianalytical Approach and Prospects with Transmission Spectroscopy

The technique of transmission spectroscopy-the variation of a planetary radius with wavelength due to opacity sources in the planet's terminator region-has been one of the most successful in the characterization of exoplanet atmospheres to date, providing key insights into the composition and structure of these distant worlds. A common assumption made when using this technique, however, is that the variations are the same in the entire terminator region. In reality, the morning and evening terminators might have distinct temperature, pressure, and thus compositional profiles due to the inherent 3D nature of the planet, which would, in turn, give rise to different spectra on each side of it. Constraining those might be fundamental for our understanding of not only the weather patterns in these distant worlds but also the planetary formation signatures that might only be possible to extract once these features are well understood. Motivated by this physical picture, in this work, we perform a detailed study of the observational prospects of detecting this effect. We present an open-source semianalytical framework with which this information can be extracted directly from transit light curves and perform a detailed study of the prospects of detecting the effect with current missions, such as TESS, and upcoming ones, such as JWST. Our results show that these missions show great promise for the detection of this effect. Transmission spectroscopy studies with JWST, in particular, could provide spectra of each of the limbs, allowing us to convey 3D information previously accessible only via phase curves.

Keywords: exoplanet atmospheres; exoplanets; exoplanet astronomy
FAST Reveals New Evidence for M94 as a Merger

We report the first high-sensitivity H I observation toward the spiral galaxy M94 with the Five-hundred-meter Aperture Spherical radio Telescope. From these observations, we discovered that M94 has a very extended H I disk, twice larger than that observed by THINGS, which is accompanied by a H I filament and seven high velocity clouds (HVCs) at different distances. The projected distances of these clouds and filaments are less than 50 kpc from the galactic center. We measured a total integrated flux (including all clouds/filament) of 127.3 ( ±1) Jy km s-1, corresponding to a H I mass of (6.51 ± 0.06)×108 M ⊙ , which is 63.0% more than that observed by THINGS. By comparing numerical simulations with the H I maps and the optical morphology of M94, we suggest that M94 is likely a remnant of a major merger of two galaxies, and the HVCs and H I filament could be the tidal features that originated from the first collision of the merger, which happened about 5 Gyr ago. Furthermore, we found a seemingly isolated H I cloud at a projection distance of 109 kpc without any optical counterpart detected. We discuss the possibilities of the origin of this cloud, such as dark dwarf galaxy and RELHIC (REionization-Limited H I Cloud). Our results demonstrate that high-sensitivity and wide-field H I imaging is important in revealing diffuse cold gas structures and tidal debris, which is crucial to understand the dynamical evolution of galaxies.

Keywords: galaxy evolution; galaxy interactions; galaxy kinematics; galaxy dynamics; h i regions
Planet Occurrence Rate Correlated to Stellar Dynamical History: Evidence from Kepler and Gaia

The dynamical history of stars influences the formation and evolution of planets significantly. To explore the influence of dynamical history on the planet formation and evolution using observations, we assume stars that experienced significantly different dynamical histories tend to have different relative velocities. Utilizing the accurate Gaia-Kepler Stellar Properties Catalog, we select single main-sequence stars and divide these stars into three groups according to their relative velocities, i.e., high-V, medium-V, and low-V stars. After considering the known biases from Kepler data and adopting prior and posterior correction to minimize the influence of stellar properties on planet occurrence rate, we find that high-V stars have a lower occurrence rate of super-Earths and sub-Neptunes (1-4 R⊕, P < 100 days) and a higher occurrence rate of sub-Earth (0.5-1 R⊕, P < 30 days) than low-V stars. Additionally, high-V stars have a lower occurrence rate of hot Jupiter-sized planets (4-20 R⊕, P < 10 days) and a slightly higher occurrence rate of warm or cold Jupiter-sized planets (4-20 R⊕, 10 < P < 400 days). After investigating multiplicity and eccentricity, we find that high-V planet hosts prefer a higher fraction of multiplanet systems and lower average eccentricity, which are consistent with the eccentricity-multiplicity dichotomy of Kepler planetary systems. All of these statistical results favor the scenario that high-V stars with large relative velocity may experience fewer gravitational events, while low-V stars may be influenced by stellar clustering significantly.

Keywords: astrostatistics; planet hosting stars; exoplanet catalogs; stellar motion; planet formation
Long-duration Gamma-Ray Burst and Associated Kilonova Emission from Fast-spinning Black Hole-Neutron Star Mergers

Gamma-ray bursts (GRBs) have been phenomenologically divided into long- and short-duration populations, generally corresponding to collapsar and compact merger origins, respectively. Here, we collect three unique bursts, GRBs 060614, 211211A, and 211227A, all of which are characterized by a long-duration main emission (ME) phase and a rebrightening extended emission (EE) phase, to study their observed properties and their potential origins as neutron star-black hole (NSBH) mergers. NS-first-born (BH-first-born) NSBH mergers tend to contain fast-spinning (nonspinning) BHs that more easily (hardly) allow tidal disruption to occur, while (without) forming electromagnetic signals. We find that NS-first-born NSBH mergers can well interpret the origins of these three GRBs, supported by the following. (1) Their X-ray MEs and EEs show unambiguous fallback accretion signatures, decreasing as ∝ t -5/3, which might account for their long durations. The EEs could result from the fallback accretion of r-process heating materials, which is predicted to occur after NSBH mergers. (2) The beaming-corrected local event-rate density for these types of merger-origin long-duration GRBs is ${{ \mathcal R }}_{0}\sim {2.4}_{-1.3}^{+2.3}\,{\mathrm{Gpc}}^{-3}\,{\mathrm{yr}}^{-1}$ , consistent with that of NS-first-born NSBH mergers. (3) Our detailed analysis of the EE, afterglow, and kilonova of the recent high-impact event GRB 211211A reveals that it could be a merger between a $\sim {1.23}_{-0.07}^{+0.06}\,{M}_{\odot }$ NS and a $\sim {8.21}_{-0.75}^{+0.77}\,{M}_{\odot }$ BH, with an aligned spin of ${\chi }_{\mathrm{BH}}\sim {0.62}_{-0.07}^{+0.06}$ , supporting an NS-first-born NSBH formation channel. A long-duration burst, with a rebrightening fallback accretion signature after the ME, and a bright kilonova, might be commonly observed features for on-axis NSBH mergers. We estimate the multimessenger detection rate between gravitational waves, GRBs, and kilonova emissions from NSBH mergers in O4 (O5) to be ~0.1 yr-1 (~1 yr-1).

Keywords: gamma-ray bursts; neutron stars; black holes; gravitational waves
Refining the Transit-timing and Photometric Analysis of TRAPPIST-1: Masses, Radii, Densities, Dynamics, and Ephemerides

We have collected transit times for the TRAPPIST-1 system with the Spitzer Space Telescope over four years. We add to these ground-based, HST, and K2 transit-time measurements, and revisit an N-body dynamical analysis of the seven-planet system using our complete set of times from which we refine the mass ratios of the planets to the star. We next carry out a photodynamical analysis of the Spitzer light curves to derive the density of the host star and the planet densities. We find that all seven planets' densities may be described with a single rocky mass-radius relation which is depleted in iron relative to Earth, with Fe 21 wt% versus 32 wt% for Earth, and otherwise Earth-like in composition. Alternatively, the planets may have an Earth-like composition but enhanced in light elements, such as a surface water layer or a core-free structure with oxidized iron in the mantle. We measure planet masses to a precision of 3%-5%, equivalent to a radial-velocity (RV) precision of 2.5 cm s-1, or two orders of magnitude more precise than current RV capabilities. We find the eccentricities of the planets are very small, the orbits are extremely coplanar, and the system is stable on 10 Myr timescales. We find evidence of infrequent timing outliers, which we cannot explain with an eighth planet; we instead account for the outliers using a robust likelihood function. We forecast JWST timing observations and speculate on possible implications of the planet densities for the formation, migration, and evolution of the planet system.

Keywords: extrasolar rocky planets; exoplanet dynamics; infrared photometry; habitable planets; transit timing variation method; transit photometry; exoplanet astronomy; planetary interior; fundamental parameters of stars; markov chain monte carlo; n-body simulations; few-body systems
Constraints on Nonlinear Tides due to p-g Mode Coupling from the Neutron Star Merger GW170817

It has been suggested by Weinberg et al. that an instability due to the nonlinear coupling of a neutron star's tide to its p- and g-modes could affect the gravitational-wave phase evolution of a neutron star binary. Weinberg suggests that this instability can turn on as the gravitational waves pass through the sensitive band of ground-based detectors, although the size of the effect is not known. The discovery of the binary neutron star merger GW170817 provides an opportunity to look for evidence of nonlinear tides from p-g mode coupling. We compute Bayesian evidences that compare waveform models that include the p-g mode coupling with models that do not. We find that the consistency between GW170817 signal and the p-g mode model reported by Abbott et al. is due to a degeneracy between the phenomenological waveform used to model the effect of nonlinear tides and the standard post-Newtonian waveform. We investigate the consistency of the GW170817 signal with regions of the parameter space where the effect of nonlinear tides is not degenerate with the standard model. Regions of the nonlinear tide parameter space that have a fitting factor of less than 99% (98.5%) are disfavored by a Bayes factor of 15 (25). We conclude that regions of the parameter space where nonlinear tides produce a measurable effect are strongly disfavored and improved theoretical modeling will be needed if future observations are to constrain nonlinear tides from p-g mode coupling in neutron stars.

Keywords: neutron stars; close binary stars; gravitational waves; compact binary stars
Spectral Evolution of the Ultraluminous X-Ray Sources M82 X-1 and X-2

M82 hosts two well-known ultraluminous X-ray sources (ULXs). X-1, an intermediate-mass black hole (IMBH) candidate, and X-2, an ultraluminous X-ray pulsar. Here, we present a broadband X-ray spectral analysis of both sources based on 10 simultaneous observations made with Chandra and NuSTAR. Chandra provides the high spatial resolution to resolve the crowded field in the 0.5-8 keV band, and NuSTAR provides the sensitive hard X-ray spectral data, extending the bandpass of our study above 10 keV. These observations, taken in 2015-2016, cover a period of flaring from X-1, allowing us to study the spectral evolution of this source with luminosity. During four of these observations, X-2 was found to be at a low flux level, allowing an unambiguous view of the emission from X-1. We find that the broadband X-ray emission from X-1 is consistent with that seen in other ULXs observed in detail with NuSTAR, with a spectrum that includes a broadened disk-like component and a high-energy tail. We find that the luminosity of the disk scales with inner disk temperature as L ∝ T-3/2, contrary to expectations of a standard accretion disk and previous results. These findings rule out a thermal state for sub-Eddington accretion, and therefore do not support M82 X-1 as an IMBH candidate. We also find evidence that the neutral column density of the material in the line of sight increases with ${L}_{{\rm{X}}}$ , perhaps due to an increased mass outflow with accretion rate. For X-2, we do not find any significant spectral evolution, but we find the spectral parameters of the phase-averaged broadband emission are consistent with the pulsed emission at the highest X-ray luminosities.

Keywords: astrophysical black holes; intermediate-mass black holes; stellar mass black holes; x-ray point sources; x-ray sources; pulsars; neutron stars
The Cygnus Loop: Shock Precursors and Electron-Ion Equilibration

The outermost edges of some supernova remnants are marked by filaments of pure Balmer line emission produced by nonradiative shock fronts. The Hα profiles of these filaments provide the shock speed and electron-proton temperature ratio in the shock. We have used the Hectochelle multiobject spectrograph on the MMT telescope to observe nine positions along the eastern nonradiative filaments of the Cygnus Loop, thereby extending the studies of Medina et al. to lower shock speeds. We complement the spectra with images from 1993 to 2020 to measure proper motions to further constrain the parameters. We also present observations of the photoionization precursor to show that the gas is strongly heated, and that the Hα emission from the precursor is dominated by collisional excitation rather than recombination.

Keywords: supernova remnants; interstellar plasma
Size and Shape Constraints of (486958) Arrokoth from Stellar Occultations

We present the results from four stellar occultations by (486958) Arrokoth, the flyby target of the New Horizons extended mission. Three of the four efforts led to positive detections of the body, and all constrained the presence of rings and other debris, finding none. Twenty-five mobile stations were deployed for 2017 June 3 and augmented by fixed telescopes. There were no positive detections from this effort. The event on 2017 July 10 was observed by the Stratospheric Observatory for Infrared Astronomy with one very short chord. Twenty-four deployed stations on 2017 July 17 resulted in five chords that clearly showed a complicated shape consistent with a contact binary with rough dimensions of 20 by 30 km for the overall outline. A visible albedo of 10% was derived from these data. Twenty-two systems were deployed for the fourth event on 2018 August 4 and resulted in two chords. The combination of the occultation data and the flyby results provides a significant refinement of the rotation period, now estimated to be 15.9380 ± 0.0005 hr. The occultation data also provided high-precision astrometric constraints on the position of the object that were crucial for supporting the navigation for the New Horizons flyby. This work demonstrates an effective method for obtaining detailed size and shape information and probing for rings and dust on distant Kuiper Belt objects as well as being an important source of positional data that can aid in spacecraft navigation that is particularly useful for small and distant bodies.

Keywords: kuiper belt; astrometry; classical kuiper belt objects; stellar occultation
An Extremely Compact, Low-mass Galaxy on its Way to Quiescence at z = 5.2

We report the discovery of a low-mass z = 5.200 ± 0.002 galaxy that is in the process of ceasing its star formation. The galaxy, MACS0417-z5BBG, is multiply imaged with magnification factors ~40 by the galaxy cluster MACS J0417.5-1154, observed as part of the CAnadian NIRISS Unbiased Cluster Survey (CANUCS). Using observations of MACS0417-z5BBG with a JWST/NIRSpec Prism spectrum and NIRCam imaging, we investigate the mechanism responsible for the cessation of star formation of the galaxy and speculate about possibilities for its future. Using spectrophotometric fitting, we find a remarkably low stellar mass of ${M}_{* }=4.3{\pm }_{0.8}^{0.9}\times {10}^{7}{M}_{\odot }$ , less than 1% of the characteristic stellar mass at z ~ 5. We measure a delensed rest-UV half-light radius in the source plane of $30{\pm }_{5}^{7}$ pc and measure a star formation rate from Hα of $0.14{\pm }_{0.12}^{0.17}$ M ⊙ yr-1. We find that under the assumption of a double power-law star formation history, MACS0417-z5BBG has seen a recent rise in star formation, peaking ~10-30 Myr ago and declining precipitously since then. Together, these measurements reveal a low-mass, extremely compact galaxy which is in the process of ceasing star formation. We investigate the possibilities of mechanisms that have led to the cessation of star formation in MACS0417-z5BBG, considering stellar and active galactic nuclei (AGN) feedback and environmental processes. We can likely rule out most environmental processes but leave open the possibility of a low-mass AGN that does not leave a broad-line imprint on the spectrum or that MACS0417-z5BBG could be a star-forming galaxy in the lull of a bursty star formation history.

Keywords: galaxies; post-starburst galaxies