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Stars in the Galactic disk are born on cold, nearly circular orbits with small vertical excursions. After their birth, their orbits evolve, driven by small- or large-scale perturbations in the Galactic disk's gravitational potential. Here, we study the vertical motions of young stars over their first few orbital periods, using a sample of OBA stars from Gaia E/DR3, which includes radial velocities and ages τ from LAMOST. We construct a parametric model for the time evolution of the stellar orbits' mean vertical actions J z as a function of Galactocentric radius, R GC. Accounting for data uncertainties, we use Markov Chain Monte Carlo analysis in annuli of Galactocentric radius (R GC) to constrain the model parameters. Our best-fit model shows a remarkably linear increase of vertical actions with age across all Galactocentric radii examined. Orbital heating by random scattering could offer a straightforward interpretation for this trend. However, various other dynamical aspects of the Galactic disk, such as stars being born in a warped disk, might offer alternative explanations that could be tested in the future. [ABSTRACT FROM AUTHOR]

In this paper, we have performed a comparative study of different types of oscillating dark energy (DE) models using the Metropolis algorithm of Markov Chain Monte Carlo. Eight different oscillating parameterizations are examined herein that have demonstrated considerable ability to fit the overall cosmological observations, including the Pantheon sample of Type Ia supernovae, baryon acoustic oscillations, cosmic chronometer Hubble data, and distance priors of the Planck cosmic microwave background. In order to compare the consistency of these models with observations, we have used both the Akaike and deviance information criteria. Although the values of the Akaike information criterion for different models indicate that there is no support for oscillating DE models, the deviance information criterion showed that there is significant support for some of these models. Our results showed that these models are capable of solving the cosmic coincidence problem and alleviating the Hubble tension. Comparing the H 0 values obtained for different oscillating scenarios with that of ΛCDM, we observed that our oscillating models led to H 0 ¯ = 69.78 , which is 0.29 greater than H 0,Λ and thus reduces the Hubble tension. Among all of the models, model 1, with H 0 = 70.00 ± 0.71, is the most capable of alleviating the H 0 tension. Furthermore, we examined our models assuming H 0 = 73.0 ± 1.4 from SHoES measurements. We find that adding this data point to our data combination led to a Δ H 0 ¯ = 0.95 increase in the H 0 value for different models. [ABSTRACT FROM AUTHOR]

The simultaneous observation of gravitational waves (GW) and prompt electromagnetic counterparts from the merger of two neutron stars can help reveal the properties of extreme matter and gravity during and immediately after the final plunge. Rapid sky localization of these sources is crucial to facilitate such multimessenger observations. As GWs from binary neutron star (BNS) mergers can spend up to 10–15 minutes in the frequency bands of the detectors at design sensitivity, early-warning alerts and premerger sky localization can be achieved for sufficiently bright sources, as demonstrated in recent studies. In this work, we present premerger BNS sky localization results using GW-SkyLocator, a deep-learning model capable of inferring sky location posterior distributions of GW sources at orders of magnitude faster speeds than standard Markov Chain Monte Carlo methods. We test our model's performance on a catalog of simulated injections from Sachdev, recovered at 0–60 s before the merger, and obtain comparable sky localization areas to the rapid localization tool BAYESTAR. These results show the feasibility of our model for premerger sky localization and the possibility of follow-up observations for precursor emissions from BNS mergers. [ABSTRACT FROM AUTHOR]

In this paper, we find the higher-order expansion parameters α and λ of spherically symmetric parameterized Rezzolla–Zhidenko (PRZ) spacetime by using its functions of the radial coordinate. We subject the parameters of this spacetime to classical tests, including weak gravitational field effects in the solar system, observations of the S2 star that is located in the star cluster close to the Sgr A⋆, and of the frequencies of selected microquasars. Based on this spherically symmetric spacetime, we perform the analytic calculations for solar system effects such as perihelion shift, light deflection, and gravitational time delay to determine limits on the parameters by using observational data. We restrict our attention to the limits on the two higher-order expansion parameters α and λ that survive at the horizon or near the horizon of spherically symmetric metrics. The properties of the expansion of these two small parameters in PRZ parameterization are discussed. We further apply Markov Chain Monte Carlo simulations to analyze and obtain the limits on the expansion parameters by using observations of the phenomena of the S2 star. Finally, we consider the epicyclic motions and derive analytic expressions of the epicyclic frequencies. Applying these expressions to the quasiperiodic oscillations of selected microquasars allows us to set further limits on the parameters of the PRZ spacetime. Our results demonstrate that the higher-order expansion parameters can be given in the range α, λ = (−0.09, 0.09) and of order ∼10−2 as a consequence of three different tests and observations. [ABSTRACT FROM AUTHOR]

We present the first version release of SESAMME, a public, Python-based full spectrum fitting tool for Simultaneous Estimates of Star-cluster Age, Metallicity, Mass, and Extinction. SESAMME compares an input spectrum of a star cluster to a grid of stellar population models with an added nebular continuum component, using Markov Chain Monte Carlo methods to sample the posterior probability distribution in four dimensions: cluster age, stellar metallicity Z, reddening E (B − V), and a normalization parameter equivalent to a cluster mass. SESAMME is highly flexible in the stellar population models that it can use to model a spectrum; our testing and initial science applications use both BPASS and Starburst99. We illustrate the ability of SESAMME to recover accurate ages and metallicities even at a moderate signal-to-noise ratio (S/N ∼ 3–5 per wavelength bin) using synthetic, noise-added model spectra of young star clusters. Finally, we test the consistency of SESAMME with other age and metallicity estimates from the literature using a sample of Hubble Space Telescope/Cosmic Origins Spectrograph far-UV spectra toward young, massive clusters in M83 and NGC 1313. We find that, on the whole, SESAMME infers star cluster properties that are consistent with the literature in both low- and high-metallicity environments. [ABSTRACT FROM AUTHOR]

It has been claimed that traditional models struggle to explain the tentative detection of the 21 cm absorption trough centered at z ∼ 17 measured by the EDGES collaboration. On the other hand, it has been shown that the EDGES results are consistent with an extrapolation of a declining UV luminosity density, following a simple power law of deep Hubble Space Telescope observations of 4 < z < 9 galaxies. We here explore the conditions by which the EDGES detection is consistent with current reionization and post-reionization observations, including the neutral hydrogen fraction at z ∼ 6–8, Thomson-scattering optical depth, and ionizing emissivity at z ∼ 5. By coupling a physically motivated source model derived from radiative transfer hydrodynamic simulations of reionization to a Markov Chain Monte Carlo sampler, we find that it is entirely possible to reconcile existing high-redshift (cosmic dawn) and low-redshift (reionization) constraints. In particular, we find that high contributions from low-mass halos along with high photon escape fractions are required to simultaneously reproduce cosmic dawn and reionization constraints. Our analysis further confirms that low-mass galaxies produce a flatter emissivity evolution, which leads to an earlier onset of reionization with a gradual and longer duration, resulting in a higher optical depth. While the models dominated by faint galaxies successfully reproduce the measured globally averaged quantities over the first one billion years, they underestimate the late redshift-instantaneous measurements in efficiently star-forming and massive systems. We show that our (simple) physically motivated semianalytical prescription produces results that are consistent with the (sophisticated) state-of-the-art THESAN radiation-magnetohydrodynamic simulation of the reionization. [ABSTRACT FROM AUTHOR]

We present a lightweight, flexible, and high-performance framework for inferring the properties of gravitational-wave events. By combining likelihood heterodyning, automatically differentiable, and accelerator-compatible waveforms, and gradient-based Markov Chain Monte Carlo sampling enhanced by normalizing flows, we achieve full Bayesian parameter estimation for real events like GW150914 and GW170817 within a minute of sampling time. Our framework does not require pretraining or explicit reparameterizations and can be generalized to handle higher dimensional problems. We present the details of our implementation and discuss trade-offs and future developments in the context of other proposed strategies for real-time parameter estimation. Our code for running the analysis is publicly available on GitHub at https://github.com/kazewong/jim. [ABSTRACT FROM AUTHOR]

The destiny of complex organic molecules (COMs) in star-forming regions is interlinked with various evolutionary phases. Therefore, identifying these species in diversified environments of identical star-forming regions would help to understand their physical and chemical heritage. We identified multiple COMs utilizing the Large Program Astrochemical Surveys At Institut de Radio Astronomie Millimétrique (IRAM) data, dedicated to chemical surveys in Sun-like star-forming regions with the IRAM 30 m telescope. It was an unbiased survey in the millimeter regime, covering the prestellar core, protostar, outflow region, and protoplanetary disk phase. Here, we report the transitions of seven COMs, namely, methanol (CH3OH), acetaldehyde (CH3CHO), methyl formate (CH3OCHO), ethanol (C2H5OH), propynal (HCCCHO), dimethyl ether (CH3OCH3), and methyl cyanide (CH3CN) in sources L1544, B1-b, IRAS4A, and SVS13A. We found a trend among these species from the derived abundances using the rotational diagram method and Monte Carlo Markov chain fitting. We have found that the abundances of all of the COMs, except for HCCCHO, increase from the L1544 (prestellar core) and peaks at IRAS16293-2422 (class 0 phase). It is noticed that the abundance of these molecules correlates with the luminosity of the sources. The obtained trend is also visible from the previous interferometric observations and considering the beam dilution effect. [ABSTRACT FROM AUTHOR]

Recent observations of the galactic centers of M87 and the Milky Way with the Event Horizon Telescope have ushered in a new era of black-hole-based tests of fundamental physics using very long baseline interferometry (VLBI). Since it is a nascent field, there are several different modeling and analysis approaches in vogue (e.g., geometric and physical models, visibility and closure amplitudes, agnostic and multimessenger priors). We present GALLIFRAY, an open-source, Python-based framework for estimation/extraction of parameters using VLBI data. It is developed with modularity, efficiency, and adaptability as the primary objectives. This article outlines the design and usage of GALLIFRAY. As an illustration, we fit a geometric and a physical model to simulated data sets using Markov Chain Monte Carlo sampling and find good convergence of the posterior distribution. We conclude with an outline of further enhancements currently in development. [ABSTRACT FROM AUTHOR]

We report the application of implicit likelihood inference to the prediction of the macroparameters of strong lensing systems with neural networks. This allows us to perform deep-learning analysis of lensing systems within a well-defined Bayesian statistical framework to explicitly impose desired priors on lensing variables, obtain accurate posteriors, and guarantee convergence to the optimal posterior in the limit of perfect performance. We train neural networks to perform a regression task to produce point estimates of lensing parameters. We then interpret these estimates as compressed statistics in our inference setup and model their likelihood function using mixture density networks. We compare our results with those of approximate Bayesian neural networks, discuss their significance, and point to future directions. Based on a test set of 100,000 strong lensing simulations, our amortized model produces accurate posteriors for any arbitrary confidence interval, with a maximum percentage deviation of 1.4% at the 21.8% confidence level, without the need for any added calibration procedure. In total, inferring 100,000 different posteriors takes a day on a single GPU, showing that the method scales well to the thousands of lenses expected to be discovered by upcoming sky surveys. [ABSTRACT FROM AUTHOR]

Motivated by the discrepancy between Bayesian and frequentist upper limits on the tensor-to-scalar ratio parameter r found by the SPIDER collaboration, we investigate whether a similar trend is also present in the latest Planck and BICEP/Keck Array data. We derive a new upper bound on r using the frequentist profile likelihood method. We vary all the relevant cosmological parameters of the ΛCDM model, as well as the nuisance parameters. Unlike the Bayesian analysis using Markov Chain Monte Carlo (MCMC), our analysis is independent of the choice of priors. Using Planck Public Release 4, BICEP/Keck Array 2018, Planck cosmic microwave background lensing, and baryon acoustic oscillation data, we find an upper limit of r < 0.037 at 95% Confidence Level (C.L.), similar to the Bayesian MCMC result of r < 0.038 for a flat prior on r and a conditioned Planck lowlEB covariance matrix. [ABSTRACT FROM AUTHOR]

This paper investigates a new methodology to search for periods in light curves of high-energy gamma-ray sources such as active galactic nuclei (AGNs). High-energy light curves have significant stochastic components, making period detection somewhat challenging. In our model, periodic terms, drifts of the light curves, and random walk with a correlation between flux points due to colored noise are taken into account independently. The parameters of the model are obtained directly from a Markov Chain Monte Carlo minimization. The time periods found are compared to the output of the publicly available Agatha program. The search method is applied to high-energy periodic AGN candidates from the Fermi-LAT catalog. The significance of periodic models over pure noise models is discussed. Finally, the variability of the period and amplitude of oscillating terms is studied on the most significant candidates. [ABSTRACT FROM AUTHOR]

We present an analysis of oscillation mode variability in the hot B subdwarf star EPIC 220422705, a new pulsator discovered from ∼78 days of K2 photometry. The high-quality light curves provide a detection of 66 significant independent frequencies, from which we identified nine incomplete potential triplets and three quintuplets. Those g- and p- multiplets give rotation periods of ∼36 and 29 days in the core and at the surface, respectively, potentially suggesting a slightly differential rotation. We derived a period spacing of 268.5 s and 159.4 s for the sequence of dipole and quadrupole modes, respectively. We characterized the precise patterns of amplitude and frequency modulations (AM and FM) of 22 frequencies with high enough amplitude for our science. Many of them exhibit intrinsic and periodic patterns of AM and FM, with periods on a timescale of months as derived by the best fitting and Markov Chain Monte Carlo test. The nonlinear resonant mode interactions could be a natural interpretation for such AMs and FMs after other mechanisms are ruled out. Our results are the first step to building a bridge between mode variability from K2 photometry and the nonlinear perturbation theory of stellar oscillation. [ABSTRACT FROM AUTHOR]

We present Atacama Large Millimeter Array band 6/7 (1.3 mm/0.87 mm) and Very Large Array Ka-band (9 mm) observations toward NGC 2071 IR, an intermediate-mass star-forming region. We characterize the continuum and associated molecular line emission toward the most luminous protostars, i.e., IRS1 and IRS3, on ∼100 au (0.″2) scales. IRS1 is partly resolved in the millimeter and centimeter continuum, which shows a potential disk. IRS3 has a well-resolved disk appearance in the millimeter continuum and is further resolved into a close binary system separated by ∼40 au at 9 mm. Both sources exhibit clear velocity gradients across their disk major axes in multiple spectral lines including C18O, H2CO, SO, SO2, and complex organic molecules like CH3OH, 13CH3OH, and CH3OCHO. We use an analytic method to fit the Keplerian rotation of the disks and give constraints on physical parameters with a Markov Chain Monte Carlo routine. The IRS3 binary system is estimated to have a total mass of 1.4â€"1.5 M ⊙. IRS1 has a central mass of 3â€"5 M ⊙ based on both kinematic modeling and its spectral energy distribution, assuming that it is dominated by a single protostar. For both IRS1 and IRS3, the inferred ejection directions from different tracers, including radio jet, water maser, molecular outflow, and H2 emission, are not always consistent, and for IRS1 these can be misaligned by ∼50°. IRS3 is better explained by a single precessing jet. A similar mechanism may be present in IRS1 as well but an unresolved multiple system in IRS1 is also possible. [ABSTRACT FROM AUTHOR]

We present Atacama Large Millimeter/submillimeter Array data on the 3 mm continuum emission, CO isotopologues (12CO, 13CO, and C18O), and high-density molecular tracers (HCN, HCO+, HNC, HNCO, CS, CN, and CH3OH) in NGC 4526. These data enable a detailed study of the physical properties of the molecular gas in a longtime resident of the Virgo Cluster; comparisons to more commonly studied spiral galaxies offer intriguing hints into the processing of molecular gas in the cluster environment. Many molecular line ratios in NGC 4526, along with our inferred abundances and CO/H2 conversion factors, are similar to those found in nearby spirals. One striking exception is the very low observed 12CO/13CO(1âˆ'0) line ratio, 3.4 ± 0.3, which is unusually low for spirals though not for Virgo Cluster early-type galaxies. We carry out radiative transfer modeling of the CO isotopologues with some archival (2âˆ'1) data, and we use Bayesian analysis with Markov Chain Monte Carlo techniques to infer the physical properties of the CO-emitting gas. We find surprisingly low [12CO/13CO] abundance ratios of 7.8 âˆ' 1.5 + 2.7 and 6.5 âˆ' 1.3 + 3.0 at radii of 0.4 kpc and 1 kpc. The emission from the high-density tracers HCN, HCO+, HNC, CS, and CN is also relatively bright, and CN is unusually optically thick in the inner parts of NGC 4526. These features hint that processing in the cluster environment may have removed much of the galaxy’s relatively diffuse, optically thinner molecular gas along with its atomic gas. Angular momentum transfer to the surrounding intracluster medium may also have caused contraction of the disk, magnifying radial gradients such as we find in [13CO/C18O]. More detailed chemical evolution modeling would be interesting in order to explore whether the unusual [12CO/13CO] abundance ratio is entirely an environmental effect or whether it also reflects the relatively old stellar population in this early-type galaxy. [ABSTRACT FROM AUTHOR]

We report Very Long Baseline Array observations of 22 GHz H2O and 43 GHz SiO masers toward the Mira variable RR Aql. By fitting the SiO maser emission to a circular ring, we estimate the absolute stellar position of RR Aql and find agreement with Gaia astrometry to within the joint uncertainty of ≈1 mas. Using the maser astrometry we measure a stellar parallax of 2.44 ± 0.07 mas, corresponding to a distance of 410 âˆ' 11 + 12 pc. The maser parallax deviates significantly from the Gaia EDR3 parallax of 1.95 ± 0.11 mas, indicating a 3.8 σ tension between radio and optical measurements. This tension is most likely caused by optical photocenter variations limiting the Gaia astrometric accuracy for this Mira variable. Combining infrared magnitudes with parallaxes for RR Aql and other Miras, we fit a periodâ€"luminosity relation using a Bayesian approach with Markov Chain Monte Carlo sampling and a strong prior for the slope of âˆ'3.60 ± 0.30 from the Large Magellanic Cloud. We find a K -band zero-point (defined at logP(days) = 2.30) of âˆ'6.79 ± 0.15 mag using very long baseline interferometry (VLBI) parallaxes and âˆ'7.08 ± 0.29 mag using Gaia parallaxes. The Gaia zero-point is statistically consistent with the more accurate VLBI value. [ABSTRACT FROM AUTHOR]

Strong high-ionization lines such as He ii of young galaxies are puzzling at high and low redshift. Although recent studies suggest the existence of nonthermal sources, whether their ionizing spectra can consistently explain multiple major emission lines remains a question. Here we derive the general shapes of the ionizing spectra for three local extremely metal-poor galaxies (EMPGs) that show strong He ii λ 4686. We parameterize the ionizing spectra composed of a blackbody and power-law radiation mimicking various stellar and nonthermal sources. We use photoionization models for nebulae and determine seven parameters of the ionizing spectra and nebulae by Markov Chain Monte Carlo methods, carefully avoiding systematics of abundance ratios. We obtain the general shapes of ionizing spectra explaining ∼10 major emission lines within observational errors with smooth connections from observed X-ray and optical continua. We find that an ionizing spectrum of one EMPG has a blackbody-dominated shape, while the others have convex downward shapes at >13.6 eV, which indicate a diversity of the ionizing spectrum shapes. We confirm that the convex downward shapes are fundamentally different from ordinary stellar spectrum shapes, and that the spectrum shapes of these galaxies are generally explained by the combination of the stellar and ultraluminous X-ray sources. Comparisons with stellar synthesis models suggest that the diversity of the spectrum shapes arises from differences in the stellar age. If galaxies at z ≳ 6 are similar to the EMPGs, high-energy (>54.4 eV) photons of the nonstellar sources negligibly contribute to cosmic reionization due to relatively weak radiation. [ABSTRACT FROM AUTHOR]

We compile a sample of 92 active galactic nuclei (AGNs) at z < 0.75 with gri photometric light curves from the archival data of the Zwicky Transient Facility and measure the accretion disk sizes via continuum reverberation mapping. We employ Monte Carlo simulation tests to assess the influences of data sampling and broad emission lines and select out the sample with adequately high sampling cadences (3 days apart in average) and minimum contaminations of broad emission lines. The interband time delays of individual AGNs are calculated using the interpolated cross-correlation function, and then these delays are fitted with a generalized accretion disk model, in which interband time delays are a power function of wavelength, black hole mass, and luminosity. A Markov Chain Monte Carlo method is adopted to determine the best parameter values. Overall the interband time delays can be fitted with the τ ∝ λ 4/3 relation as predicted from a steady-state, optically thick, geometrically thin accretion disk; however, the yielded disk size is systematically larger than expected, although the ratio of the measured to theoretical disk sizes depends on using the emissivity- or responsivity-weighted disk radius. These results are broadly consistent with previous studies, all together raising a puzzle about the “standard” accretion disk model. [ABSTRACT FROM AUTHOR]

A reliable estimate of the redshift distribution n (z) is crucial for using weak gravitational lensing and large-scale structures of galaxy catalogs to study cosmology. Spectroscopic redshifts for the dim and numerous galaxies of next-generation weak-lensing surveys are expected to be unavailable, making photometric redshift (photo- z) probability density functions (PDFs) the next best alternative for comprehensively encapsulating the nontrivial systematics affecting photo- z point estimation. The established stacked estimator of n (z) avoids reducing photo- z PDFs to point estimates but yields a systematically biased estimate of n (z) that worsens with a decreasing signal-to-noise ratio, the very regime where photo- z PDFs are most necessary. We introduce Cosmological Hierarchical Inference with Probabilistic Photometric Redshifts (CHIPPR), a statistically rigorous probabilistic graphical model of redshift-dependent photometry that correctly propagates the redshift uncertainty information beyond the best-fit estimator of n (z) produced by traditional procedures and is provably the only self-consistent way to recover n (z) from photo- z PDFs. We present the chippr prototype code, noting that the mathematically justifiable approach incurs computational cost. The CHIPPR approach is applicable to any one-point statistic of any random variable, provided the prior probability density used to produce the posteriors is explicitly known; if the prior is implicit, as may be the case for popular photo- z techniques, then the resulting posterior PDFs cannot be used for scientific inference. We therefore recommend that the photo- z community focus on developing methodologies that enable the recovery of photo- z likelihoods with support over all redshifts, either directly or via a known prior probability density. [ABSTRACT FROM AUTHOR]

We apply a conventional accretion disk model to the FU Oriâ€"type objects HBC 722 and Gaia 17bpi. Our base model is a steady-state, thin Keplerian disk featuring a modified Shakuraâ€"Sunyaev temperature profile, with each annulus radiating as an area-weighted spectrum given by a NextGen atmosphere at the appropriate temperature. We explore departures from the standard model by altering the temperature distribution in the innermost region of the disk to account for “boundary region”â€"like effects. We consider the overall spectral energy distribution as well as medium- and high-resolution spectra in evaluating best-fit models to the data. Parameter degeneracies are studied via a Markov Chain Monte Carlo parameter estimation technique. Allowing all parameters to vary, we find accretion rates for HBC 722 of M ̇ = 10 âˆ' 4.90 M ⊙ yr âˆ' 1 âˆ' 0.40 + 0.99 dex and for Gaia 17bpi of M ̇ = 10 âˆ' 6.70 M ⊙ yr âˆ' 1 âˆ' 0.36 + 0.46 dex ; the corresponding maximum disk temperatures are 7100 âˆ' 500 + 300 K and 7900 âˆ' 400 + 900 K, respectively. While the accretion rate of HBC 722 is on the same order as other FU Oriâ€"type objects, Gaia 17bpi has a lower rate than previously reported as typical, commensurate with its lower luminosity. Alternate models that fix some disk or stellar parameters are also presented, with tighter confidence intervals on the remaining fitted parameters. In order to improve upon the somewhat large credible intervals for the M ̇ values, and to make progress on boundary layer characterization, flux-calibrated ultraviolet spectroscopy is needed. [ABSTRACT FROM AUTHOR]

We present accretion-disk structure measurements from UV–optical reverberation mapping (RM) observations of a sample of eight quasars at 0.24 < z < 0.85. Ultraviolet photometry comes from two cycles of Hubble Space Telescope monitoring, accompanied by multiband optical monitoring by the Las Cumbres Observatory network and Liverpool Telescopes. The targets were selected from the Sloan Digital Sky Survey Reverberation Mapping project sample with reliable black hole mass measurements from Hβ RM results. We measure significant lags between the UV and various optical griz bands using JAVELIN and CREAM methods. We use the significant lag results from both methods to fit the accretion-disk structure using a Markov Chain Monte Carlo approach. We study the accretion disk as a function of disk normalization, temperature scaling, and efficiency. We find direct evidence for diffuse nebular emission from Balmer and Fe ii lines over discrete wavelength ranges. We also find that our best-fit disk color profile is broadly consistent with the Shakura & Sunyaev disk model. We compare our UV–optical lags to the disk sizes inferred from optical–optical lags of the same quasars and find that our results are consistent with these quasars being drawn from a limited high-lag subset of the broader population. Our results are therefore broadly consistent with models that suggest longer disk lags in a subset of quasars, for example, due to a nonzero size of the ionizing corona and/or magnetic heating contributing to the disk response. [ABSTRACT FROM AUTHOR]

Tomographic three-dimensional 21 cm images from the epoch of reionization contain a wealth of information about the reionization of the intergalactic medium by astrophysical sources. Conventional power spectrum analysis cannot exploit the full information in the 21 cm data because the 21 cm signal is highly non-Gaussian due to reionization patchiness. We perform a Bayesian inference of the reionization parameters where the likelihood is implicitly defined through forward simulations using density estimation likelihood-free inference (DELFI). We adopt a trained 3D convolutional neural network (CNN) to compress the 3D image data into informative summaries (DELFI-3D CNN). We show that this method recovers accurate posterior distributions for the reionization parameters. Our approach outperforms earlier analysis based on two-dimensional 21 cm images. In contrast, a Monte Carlo Markov Chain analysis of the 3D light-cone-based 21 cm power spectrum alone and using a standard explicit likelihood approximation results in less accurate credible parameter regions than inferred by the DELFI-3D CNN, both in terms of the location and shape of the contours. Our proof-of-concept study implies that the DELFI-3D CNN can effectively exploit more information in the 3D 21 cm images than a 2D CNN or power spectrum analysis. This technique can be readily extended to include realistic effects and is therefore a promising approach for the scientific interpretation of future 21 cm observation data. [ABSTRACT FROM AUTHOR]

We provide a method for estimating the projected density distribution n ÂŻ 2 w p (r p) of photometric objects around spectroscopic objects in a spectroscopic survey. This quantity describes the distribution of photometric sources with certain physical properties (e.g., luminosity, mass, and color) around cosmic webs (PAC) traced by the spectroscopic objects. The method can make full use of current and future deep and wide photometric surveys to explore the formation of galaxies up to medium redshift (z s < 2) 33 Throughout the paper, we use z s for redshift, z for the z -band magnitude, z p for the photometric redshift. with the aid of cosmological spectroscopic surveys that sample only a fairly limited species of objects (e.g., emission line galaxies). As an example, we apply the PAC method to the CMASS spectroscopic and HSC-SSP PDR2 photometric samples to explore the distribution of galaxies for a wide range of stellar masses from 109.0 to 1012.0 M ⊙ around massive stars at z s ≈ 0.6. Using the abundance-matching method, we model n ÂŻ 2 w p (r p) in N -body simulation using Markov chain Monte Carlo sampling, and we accurately measure the stellarâ€"halo mass relation and stellar mass function for the whole mass range. We can also measure the conditional stellar mass function of satellites for central galaxies of different mass. The PAC method has many potential applications for studying the evolution of galaxies. [ABSTRACT FROM AUTHOR]

It has been long debated whether the high-energy gamma-ray radiation from the Crab Nebula stems from leptonic or hadronic processes. In this work, we investigate the multiband nonthermal radiation from the Crab pulsar wind nebula with the leptonic and leptonicâ€"hadronic hybrid models, respectively. Then we use the Markov Chain Monte Carlo sampling technology and method of sampling trace to study the stability and reasonability of the model parameters according to the recently observed results and obtain the best-fitting values of parameters. Finally, we calculate different radiative components generated by the electrons and protons in the Crab Nebula. The modeling results indicate that the pure leptonic origin model with the one-zone only can partly agree with some segments of the data from various experiments (including the PeV gamma-ray emission reported by the LHAASO and the other radiation ranging from the radio to very-high-energy gamma-ray wave band), and the contribution of hadronic interaction is hardly constrained. However, we find that the hadronic process may also contribute, especially in the energy range exceeding the PeV. In addition, it can be inferred that the higher energy signals from the Crab Nebula could be observed in the future. [ABSTRACT FROM AUTHOR]

A relativistic electron–positron (e+e−) pair wind from a rapidly rotating, strongly magnetized neutron star (NS) would interact with a gamma-ray burst (GRB) external shock and reshape afterglow emission signatures. Assuming that the merger remnant of GW170817 is a long-lived NS, we show that a relativistic e+e− pair wind model with a simple top-hat jet viewed off-axis can reproduce multiwavelength afterglow lightcurves and superluminal motion of GRB 170817A. The Markov Chain Monte Carlo (MCMC) method is adopted to obtain the best-fitting parameters, which give the jet half-opening angle θj ≈ 0.12 rad, and the viewing angle θv ≈ 0.23 rad. The best-fitting value of θv is close to the lower limit of the prior that is chosen based on the gravitational-wave and electromagnetic observations. In addition, we also derive the initial Lorentz factor Γ0 ≈ 49 and the isotropic kinetic energy EK,iso ≈ 1× 1052 erg. Consistency between the corrected on-axis values for GRB 170817A and typical values observed for short GRBs indicates that our model can also reproduce the prompt emission of GRB 170817A. An NS with a magnetic field strength Bp ≈ 1.6 × 1013 G is obtained in our fitting, indicating that a relatively low thermalization efficiency η ≲ 10−3 is needed to satisfy observational constraints on the kilonova. Furthermore, our model is able to reproduce a late-time shallow decay in the X-ray lightcurve, and predicts that the X-ray and radio flux will continue to decline in the coming years. [ABSTRACT FROM AUTHOR]

Abrupt deflections of the magnetic field in the solar wind, so called "switchbacks," are frequently observed by the Parker Solar Probe (PSP) during its first two orbits and are believed to play an important role in unveiling the nature of solar corona heating and solar wind acceleration in the inner heliosphere. Many attempts were made recently to understand the nature of switchbacks. However, the origin, propagation, and evolution of switchbacks are still under debate. In this study, we attempt to use the linear theory of Zank et al. to interpret the switchback observations. We select 96 simple one-humped switchback events during the first encounter of PSP and use a Markov Chain Monte Carlo technique to fit the observed magnetic field and plasma variables with the model predictions for each event. The chi-squared goodness-of-fit test is used to evaluate the fittings. We find that about 47.9% and 42.7% of the events are accepted as good fits below the 95% and 90% critical values, respectively. This statistical study validates the reliability of the linear theory of Zank et al. for a significant number of switchback events. The statistical analysis provides the most probable initial conditions for switchbacks generated by interchange reconnection, which provides insight into the environment at which interchange reconnection was occurring. [ABSTRACT FROM AUTHOR]

We present a novel scenario in which light (∼few eV) dark fermions (sterile neutrinos) interact with a scalar field as in mass-varying neutrino dark energy theories. As the eV sterile states naturally become nonrelativistic before the matter–radiation equality (MRE), we show that the neutrino–scalar fluid develops strong perturbative instability followed by the formation of neutrino nuggets, and the early dark energy (EDE) behavior disappears around MRE. The stability of the nugget is achieved when the Fermi pressure balances the attractive scalar force, and we numerically find the mass and radius of heavy cold nuggets by solving for the static configuration for the scalar field. We find that for the case when dark matter nugget density is subdominant and most of the EDE go into scalar field dynamics, it can in principle relax the Hubble anomaly. Especially when a kinetic-energy-dominated phase appears after the phase transition, the DE density dilutes faster than radiation and satisfies the requirements for solving the H0 anomaly. In our scenario, unlike in originally proposed early DE theory, the DE density is controlled by (eV) neutrino mass and it does not require a fine-tuned EDE scale. We perform a Markov Chain Monte Carlo analysis and confront our model with Planck + SHOES and baryon acoustic oscillation data and find evidence for a nonzero neutrino–scalar EDE density during MRE. Our analysis shows that this model is in agreement to nearly 1.3σ with SHOES measurement, which is H0 = 74.03 ± 1.42 km s−1 Mpc−1. [ABSTRACT FROM AUTHOR]

We use a time-dependent hydrodynamic code and a non-LTE Monte Carlo code to model disk dissipation for the Be star 66 Ophiuchi. We compiled 63 years of observations from 1957 to 2020 to encompass the complete history of the growth and subsequent dissipation of the star's disk. Our models are constrained by new and archival photometry, spectroscopy, and polarization observations, allowing us to model the disk dissipation event. Using Markov Chain Monte Carlo methods, we find that the properties of 66 Oph are consistent with those of a standard B2Ve star. We computed a grid of 61,568 Be star disk models to constrain the density profile of the disk before dissipation using observations of the Hα line profile and spectral energy distribution. We find at the onset of dissipation the disk has a base density of 2.5 × 10−11 g cm−3 with a radial power-law index of n = 2.6. Our models indicate that after 21 yr of disk dissipation 66 Oph's outer disk remained present and bright in the radio. We find an isothermal disk with constant viscosity with an α = 0.4 and an outer disk radius of ∼115 stellar radii best reproduces the rate of 66 Oph's disk dissipation. We determined the interstellar polarization in the direction of the star in the V band is p = 0.63 ± 0.02% with a polarization position angle of θIS ≈ 85.°7 ± 0.°7. Using the Stokes QU diagram, we find the intrinsic polarization position angle of 66 Oph's disk is θint ≈ 98° ± 3°. [ABSTRACT FROM AUTHOR]

The present work explores the origin of the formation of star clusters in our Galaxy and in the Small Magellanic Cloud (SMC) through simulated H-R diagrams and compare those with observed star clusters. The simulation study produces synthetic H-R diagrams through the Markov Chain Monte Carlo (MCMC) technique using the star formation history (SFH), luminosity function (LF), abundance of heavy metal (Z), and a big library of isochrones as basic inputs and compares them with observed H-R diagrams of various star clusters. The distance-based comparison between those two diagrams is carried out through two-dimensional matching of points in the color−magnitude diagram (CMD) after the optimal choice of bin size and appropriate distance function. It is found that in a poor medium of heavy elements (Z = 0.0004), the Gaia LF along with a mixture of multiple Gaussian distributions of the SFH may be the origin of formation of globular clusters (GCs). On the contrary, an enriched medium (Z = 0.019) is generally favored with the Gaia LF along with a double power law or Beta-type (i.e., unimodal) SFH, for the formation of globular clusters. For SMC clusters, the choice of an exponential LF and exponential SFH is the proper combination for a poor medium, whereas the Gaia LF with a Beta-type SFH is preferred for the formation of star clusters in an enriched medium. [ABSTRACT FROM AUTHOR]

Delta-gravity (DG) is a gravitational model based on an extension of general relativity given by a new symmetry called. In this model, new matter fields are added to the original matter fields, motivated by the additional symmetry. We call them matter fields. This model predicts an accelerating universe without the need to introduce a cosmological constant. In this work, we study the scalar cosmic microwave background (CMB) temperature (TT) power spectrum predicted by DG using an analytical hydrodynamic approach. To fit the Planck satellite's data with the DG model, we used a Markov Chain Monte Carlo analysis. We also include a study about the compatibility between Type Ia supernovae (SNe Ia) and CMB observations in the DG context. Finally, we obtain the scalar CMB TT power spectrum and the fitted parameters needed to explain both SN Ia data and CMB measurements. The results are in reasonable agreement with both observations considering the analytical approximation. We also discuss whether the Hubble constant and the accelerating universe are in concordance with the observational evidence in the DG context. [ABSTRACT FROM AUTHOR]

Motivated by the recent discovery of a compact object with mass in the range 2.5–2.67 M⊙ in the binary merger GW190814, we revisit the question of the maximum mass of neutron stars (NSs). We use a Markov Chain Monte Carlo approach to generate about two million phenomenological equations of state with and without first-order phase transitions. We fix the crust equation of state and only assume causality at higher densities. We show how a strict upper bound on the maximum NS mass can be inferred from upcoming observation of NS radii and masses. The derived upper bounds depend only on relativity and causality, so it is not affected by nuclear physics uncertainties. We show how a lower limit on the maximum mass of NSs, in combination with upcoming measurements of NS radii by LIGO/Virgo and NICER, would constrain the equation of state of dense matter. Finally, we discuss the implications for GW190814. [ABSTRACT FROM AUTHOR]

Lanthanide element signatures are key to understanding many astrophysical observables, from merger kilonova light curves to stellar and solar abundances. To learn about the lanthanide element synthesis that enriched our solar system, we apply the statistical method of Markov Chain Monte Carlo to examine the nuclear masses capable of forming the r-process rare-earth abundance peak. We describe the physical constraints we implement with this statistical approach and demonstrate the use of the parallel chains method to explore the multidimensional parameter space. We apply our procedure to three moderately neutron-rich astrophysical outflows with distinct types of r-process dynamics. We show that the mass solutions found are dependent on outflow conditions and are related to the r-process path. We describe in detail the mechanism behind peak formation in each case. We then compare our mass predictions for neutron-rich neodymium and samarium isotopes to the latest experimental data from the CPT at CARIBU. We find our mass predictions given outflows that undergo an extended (n,γ)⇄(γ,n) equilibrium to be those most compatible with both observational solar abundances and neutron-rich mass measurements. [ABSTRACT FROM AUTHOR]

Modeling of the NICER X-ray waveform of the pulsar PSR J0030+0451, aimed at constraining the neutron star mass and radius, has inferred surface hot spots (the magnetic polar caps) that imply significantly nondipolar magnetic fields. To this end, we investigate magnetic field configurations that comprise offset dipole-plus-quadrupole components using a static vacuum field and force-free global magnetosphere models. Taking into account the compactness and observer angle values provided by Miller et al. and Riley et al., we compute geodesics from the observer plane to the polar caps to compute the resulting X-ray light curve. We explore, through Markov Chain Monte Carlo techniques, the detailed magnetic field configurations that can reproduce the observed X-ray light curve and have discovered degeneracies, i.e., diverse field configurations, which can provide sufficient descriptions of the NICER X-ray waveforms. Having obtained the force-free field structures, we then compute the corresponding synchronous γ-ray light curves following Kalapotharakos et al.; these we compare to those obtained by Fermi-LAT, to provide models consistent with both the X-ray and the γ-ray data, thereby restricting further the multipole field parameters. An essential aspect of this approach is the proper computation of the relative phase between the synchronous X- and γ-ray light curves. We conclude with a discussion of the broader implications of our study. [ABSTRACT FROM AUTHOR]

Relativistic shocks propagating into a medium with low magnetization are generated and sustained by small-scale but very strong magnetic field turbulence. This so-called "microturbulence" modifies the typical shock acceleration process, and in particular that of electrons. In this work we perform Monte Carlo (MC) simulations of electrons encountering shocks with microturbulent fields. The simulations cover a three-dimensional parameter space in shock speed, acceleration efficiency, and peak magnetic field strength. From these, a Markov Chain Monte Carlo (MCMC) method was employed to estimate the maximum electron momentum from the MC-simulated electron spectra. Having estimated this quantity at many points well-distributed over an astrophysically relevant parameter space, an MCMC method was again used to estimate the parameters of an empirical formula that computes the maximum momentum of a Fermi-accelerated electron population anywhere in this parameter space. The maximum energy is well-approximated as a broken power law in shock speed, with the break occurring when the shock decelerates to the point where electrons can begin to escape upstream from the shock. [ABSTRACT FROM AUTHOR]

How do active galactic nuclei with low optical luminosities produce powerful radio emission? Recent studies of active galactic nuclei with moderate radio and low optical luminosities (Fanaroff & Riley class I, FR I) searching for broad nuclear emission lines in polarized light, as predicted by some active galactic nucleus unification models, have found heterogeneous results. These models typically consist of a central engine surrounded by a torus of discrete dusty clouds. These clouds would absorb and scatter optical emission, blocking broad nuclear emission lines, and reradiate in mid-infrared. Some scattered broad-line emission may be observable, depending on geometry, which would be polarized. We present a wide-band infrared spectroscopic analysis of 10 nearby FR I radio galaxies to determine whether there is significant emission from a dusty obscuring structure. We used Markov Chain Monte Carlo algorithms to decompose Spitzer/IRS spectra of our sample. We constrained the wide-band behavior of our models with photometry from the Two Micron All Sky Survey, Spitzer/IRAC, Spitzer/MIPS, and Herschel/SPIRE. We find that one galaxy is best fit by a clumpy torus and three others show some thermal mid-infrared component. This suggests that in those three there is likely some obscuring dust structure that is inconsistent with our torus models and there must be some source of photons heating the dust. We conclude that 40% of our FR I radio galaxies show evidence of obscuring dusty material, possibly some other form of hidden broad-line nucleus, but only 10% favor the clumpy torus model specifically. [ABSTRACT FROM AUTHOR]

We present multiwavelength modeling of the afterglow from the long γ-ray burst (GRB) 160625B using Markov Chain Monte Carlo techniques of the afterglowpy Python package. GRB 160625B is an extremely bright burst with a rich set of observations spanning from radio to γ-ray frequencies. These observations range from ∼0.1 days to >1000 days, thus making this event extremely well suited to such modeling. In this work we compare top-hat and Gaussian jet structure types in order to find best-fit values for the GRB jet collimation angle, viewing angle, and other physical parameters. We find that a Gaussian-shaped jet is preferred (2.7σ–5.3σ) over the traditional top-hat model. Our estimate for the opening angle of the burst ranges from 1.°26 to 3.°90, depending on jet-shape model. We also discuss the implications that assumptions on jet shape, viewing angle, and particularly the participation a fraction of electrons have on the final estimation of GRB intrinsic energy release and the resulting energy budget of the relativistic outflow. Most notably, allowing the participation fraction to vary results in an estimated total relativistic energy of ∼1053 erg. This is two orders of magnitude higher than when the total fraction is assumed to be unity; thus, this parameter has strong relevance for placing constraints on long GRB central engines, details of the circumburst media, and host environment. [ABSTRACT FROM AUTHOR]

We study the effect of variations in dust size distribution and composition on the correlation between the spectral shape of extinction (parameterized by RV) and far-infrared dust emissivity (parameterized by the power-law index β). Starting from the size distribution models proposed by Weingartner & Draine, using the dust absorption and emission properties derived by Laor & Draine for carbonaceous and silicate grains, and by Li & Draine for polycyclic aromatic hydrocarbon grains, we calculate the extinction and compare it with the reddening vector derived by Schlafly et al. An optimizer and an Markov chain Monte Carlo method are used to explore the space of available parameters for the size distributions. We find that larger grains are correlated with high RV. However, this trend is not enough to explain the emission-extinction correlation observed by Schlafly et al. For the RV − β correlation to arise, we need to impose explicit priors for the carbonaceous and silicate volume priors as functions of RV. The results show that a composition with higher ratio of carbonaceous to silicate grains leads to higher RV and lower β. A relation between E(B − V)/τ353 and RV is apparent, with possible consequences for the recalibration of emission-based dust maps as a function of RV. [ABSTRACT FROM AUTHOR]

We present a reanalysis of the cumulative ACIS-S Chandra data set pointed at the double active galactic nuclei (AGNs) of the NGC 6240 merging galaxy, focusing on the hard energy bands containing the hard spectral continuum (5.5–5.9 keV), the redshifted Fe i Kα line (6.0–6.4 keV), and the redshifted Fe xxv line (6.4–6.7 keV). We have used the full Chandra telescope angular resolution and modeled the Chandra point-spread function (PSF) by comparing a preflight calibration model to the data for the two bright AGNs. With two complementary approaches—(1) studying the residuals after PSF subtraction and (2) producing reconstructed Expectation through Markov Chain Monte Carlo (EMC2) images—we are able to resolve structures extending from ∼1 kpc to <200 pc in the S AGN. The latter are within the sphere of influence of this BH. We find significant extended emission in both continuum and Fe lines in the ∼2″ (∼1 kpc) region surrounding the nuclei, in the region between the N and S AGN, and in a sector of PA 120–210 deg. extending to the SE from the centroid of the S AGN surface brightness. The extended Fe i Kα emission is likely to originate from the fluorescence of X-ray photons interacting with dense molecular clouds, providing a complementary view to recent high-resolution Atacama Large Millimeter/submillimeter Array (ALMA) studies. The nonthermal emission is more prevalent in the region in between the two active X-ray nuclei and in the N AGN. We do not find strong evidence of X-ray emission associated with the third nucleus recently proposed for NGC 6240. [ABSTRACT FROM AUTHOR]

We present the first asymmetric drift (AD) measurements for unresolved stellar populations of different characteristic ages above and below 1.5 Gyr. These measurements sample the age–velocity relation in galaxy disks. In this first paper, we develop two efficient algorithms to extract AD on a spaxel-by-spaxel basis from optical integral-field spectroscopic data cubes. The algorithms apply different spectral templates, one using simple stellar populations and the other a stellar library; their comparison allows us to assess systematic errors in derived multicomponent velocities, such as template mismatch. We test algorithm reliability using mock spectra and Monte Carlo Markov Chains on real data from the MaNGA survey in Sloan Digital Sky Survey IV. We quantify random and systematic errors in AD as a function of signal-to-noise and stellar population properties with the aim of applying this technique to large subsets of the MaNGA galaxy sample. As a demonstration of our methods, we apply them to an initial sample of seven galaxies with comparable stellar mass and color to the Milky Way. We find a wide range of distinct AD radial profiles for young and old stellar populations. [ABSTRACT FROM AUTHOR]

In the context of a cosmography approach to using the data of the Hubble diagram for supernovae, quasars, and gamma-ray bursts, we study dark energy (DE) parameterizations and the concordance cold dark matter (ΛCDM) universe. Using different combinations of data samples including (i) supernovae (Pantheon), (ii) Pantheon + quasars. and (iii) Pantheon + quasars + gamma-ray bursts, and applying the minimization of χ2 function of the distance modulus of data samples in the context of the Markov Chain Monte Carlo method, we obtain constrained values of cosmographic parameters in a model-independent cosmography scenario. We then investigate our analysis, for different concordance ΛCDM cosmology, wCDM, Chevallier–Polarski–Linder, and Pade parameterizations. Comparing the numerical values of the cosmographic parameters obtained for DE scenarios with those of the model-independent method, we show that the concordance ΛCDM model has serious issues when we involve quasar and gamma-ray burst data in our analysis. While high-redshift quasars and gamma-ray bursts can falsify the concordance model, our results using a cosmography approach indicate that the other DE parameterizations are still consistent with these observations. [ABSTRACT FROM AUTHOR]

We report on a Hubble Space Telescope search for rest-frame ultraviolet emission from the host galaxies of five far-infrared-luminous z ≃ 6 quasars and the z = 5.85 hot-dust-free quasar SDSS J0005–0006. We perform 2D surface brightness modeling for each quasar using a Markov Chain Monte Carlo estimator, to simultaneously fit and subtract the quasar point source in order to constrain the underlying host galaxy emission. We measure upper limits for the quasar host galaxies of mJ > 22.7 mag and mH > 22.4 mag, corresponding to stellar masses of M* < 2 × 1011M⊙. These stellar mass limits are consistent with the local MBH − M* relation. Our flux limits are consistent with those predicted for the UV stellar populations of z ≃ 6 host galaxies, but likely in the presence of significant dust (mag). We also detect a total of up to nine potential z ≃ 6 quasar companion galaxies surrounding five of the six quasars, separated from the quasars by 1.″4–3.″2, or 8.4–19.4 kpc, which may be interacting with the quasar hosts. These nearby companion galaxies have UV absolute magnitudes of −22.1 to −19.9 mag and UV spectral slopes β of −2.0 to −0.2, consistent with luminous star-forming galaxies at z ≃ 6. These results suggest that the quasars are in dense environments typical of luminous z ≃ 6 galaxies. However, we cannot rule out the possibility that some of these companions are foreground interlopers. Infrared observations with the James Webb Space Telescope will be needed to detect the z ≃ 6 quasar host galaxies and better constrain their stellar mass and dust content. [ABSTRACT FROM AUTHOR]

We reconstruct the expansion history of the universe using type Ia supernovae (SN Ia) in a manner independent of any cosmological model assumptions. To do so, we implement a nonparametric iterative smoothing method on the Joint Light-curve Analysis (JLA) data while exploring the SN Ia light-curve hyperparameter space by Markov Chain Monte Carlo (MCMC) sampling. We test to see how the posteriors of these hyperparameters depend on cosmology, whether using different dark energy models or reconstructions shift these posteriors. Our constraints on the SN Ia light-curve hyperparameters from our model-independent analysis are very consistent with the constraints from using different parameterizations of the equation of state of dark energy, namely the flat ΛCDM cosmology, the Chevallier–Polarski–Linder model, and the Phenomenologically Emergent Dark Energy (PEDE) model. This implies that the distance moduli constructed from the JLA data are mostly independent of the cosmological models. We also studied that the possibility the light-curve parameters evolve with redshift and our results show consistency with no evolution. The reconstructed expansion history of the universe and dark energy properties also seem to be in good agreement with the expectations of the standard ΛCDM model. However, our results also indicate that the data still allow for considerable flexibility in the expansion history of the universe. [ABSTRACT FROM AUTHOR]

With the published data of apparent axis ratios for 1109 ultra-diffuse galaxies (UDGs) located in 17 low-redshift (z ∼ 0.020–0.063) galaxy clusters and 84 UDGs in two intermediate-redshift (z ∼ 0.308–0.348) clusters, we take advantage of a Markov Chain Monte Carlo approach and assume a triaxial model to investigate the intrinsic morphologies of UDGs. In contrast to the conclusion of Burkert, i.e., the underlying shapes of UDGs are purely prolate (C = B < A), we find that the data favor the oblate-triaxial models (i.e., thick disks with) over the nearly prolate ones. We also find that the intrinsic morphologies of UDGs are related to their stellar masses/luminosities, environments, and redshifts. First, the more luminous UDGs have puffier morphologies compared with the less luminous counterparts; the UDG morphologic dependence on luminosity is distinct from that of the typical quiescent dwarf ellipticals (dEs) and dwarf spheroidals (dSphs); in this sense, UDGs may not be simply treated as an extension of the dE/dSph class with similar evolutionary histories; they may differ not only in size. Second, the UDGs with smaller clustercentric distances are more puffed up, compared with the counterparts with larger clustercentric distances; in combination with the UDG thickness dependence on luminosity, the puffier morphologies of UDGs with high luminosities or located in the denser environments are very likely to be attributed to tidal interactions with massive galaxies. Third, we find that the intermediate-redshift UDGs are more flattened, compared with the low-redshift counterparts, which plausibly suggests a "disky" origin for the high-redshift, newly born UDGs. [ABSTRACT FROM AUTHOR]

We present MCSED , a new spectral energy distribution (SED) fitting code that mates flexible stellar evolution calculations with the Markov Chain Monte Carlo algorithms of the software package emcee. It takes broad-, intermediate-, and narrowband photometry, emission-line fluxes, and/or absorption-line spectral indices and returns probability distributions and covariance plots for all model parameters. It includes a variety of dust attenuation curves with parameters for varying the UV slopes and bump strengths, a prescription for continuum and polycyclic aromatic hydrocarbon emission from dust, models for continuum and line emission from ionized gas, options for fixed and variable stellar metallicity, and a selection of star formation rate (SFR) histories. The code is well suited for exploring parameter interdependencies in sets of galaxies with known redshifts for which there is multiband photometry and/or spectroscopy. We apply MCSED to a sample of ∼2000 galaxies in the five CANDELS fields that were selected via their strong [O iii ] λ5007 emission, and we explore the systematic behavior of their SEDs. We find that the galaxies become redder with stellar mass due to both increasing internal attenuation and a greater population of older stars. The slope of the UV extinction curve also changes with stellar mass, and at least some galaxies exhibit an extinction excess at 2175 Å. Finally, we demonstrate that below M ≲ 109M⊙, the shape of the star-forming galaxy main sequence is highly dependent on the galaxies' assumed SFR history, as calculations that assume a constant SFR produce stellar masses that are ∼1 dex smaller than those found using more realistic SFR histories. [ABSTRACT FROM AUTHOR]

We present the completion of a data analysis pipeline that self-consistently separates global 21 cm signals from large systematics using a pattern recognition technique. This pipeline will be used for both ground and space-based hydrogen cosmology instruments. In the first paper of this series, we obtain optimal basis vectors from signal and foreground training sets to linearly fit both components with the minimal number of terms that best extracts the signal given its overlap with the foreground. In this second paper, we utilize the spectral constraints derived in the first paper to calculate the full posterior probability distribution of any signal parameter space of choice. The spectral fit provides the starting point for a Markov Chain Monte Carlo (MCMC) engine that samples the signal without traversing the foreground parameter space. At each MCMC step, we marginalize over the weights of all linear foreground modes and suppress those with unimportant variations by applying priors gleaned from the training set. This method drastically reduces the number of MCMC parameters, augmenting the efficiency of exploration, circumvents the need for selecting a minimal number of foreground modes, and allows the complexity of the foreground model to be greatly increased to simultaneously describe many observed spectra without requiring extra MCMC parameters. Using two nonlinear signal models, one based on the Experiment to Detect the Global Epoch-of-Reionization Signature (EDGES) observations and the other on phenomenological frequencies and temperatures of theoretically expected extrema, we demonstrate the success of this methodology by recovering the input parameters from multiple randomly simulated signals at low radio frequencies (10–200 MHz), while rigorously accounting for realistically modeled beam-weighted foregrounds. [ABSTRACT FROM AUTHOR]

We have obtained Gemini Planet Imager (GPI) J-, H-, K1-, and K2-Spec observations of the iconic debris ring around the young, main-sequence star HR 4796A. We applied several point-spread function (PSF) subtraction techniques to the observations (Mask-and-Interpolate, RDI-NMF, RDI-KLIP, and ADI-KLIP) to measure the geometric parameters and the scattering phase function for the disk. To understand the systematic errors associated with PSF subtraction, we also forward-modeled the observations using a Markov Chain Monte Carlo framework and a simple model for the disk. We found that measurements of the disk geometric parameters were robust, with all of our analyses yielding consistent results; however, measurements of the scattering phase function were challenging to reconstruct from PSF-subtracted images, despite extensive testing. As a result, we estimated the scattering phase function using disk modeling. We searched for a dependence of the scattering phase function with respect to the GPI filters but found none. We compared the H-band scattering phase function with that measured by Hubble Space Telescope STIS at visual wavelengths and discovered a blue color at small scattering angles and a red color at large scattering angles, consistent with predictions and laboratory measurements of large grains. Finally, we successfully modeled the SPHERE H2 HR 4796A scattered phase function using a distribution of hollow spheres composed of silicates, carbon, and metallic iron. [ABSTRACT FROM AUTHOR]

We report on resolving power measurements of an X-ray reflection grating designed for use in an astronomical soft X-ray spectrograph. The grating was patterned via electron-beam lithography (EBL) to have fanned grooves to match the convergence of an illuminating beam. Grating measurements were conducted in an echelle-like mounting, which yields access to high diffraction orders in the soft X-ray bandpass (0.2–2.0 keV). By comparing the zeroth-order line-spread function to the telescope focus, we find evidence for minimal broadening (<1″) introduced by the figure of the grating. In addition, we fit for the spectral resolution (R = λ/Δλ) intrinsic to this grating using a Bayesian Markov Chain Monte Carlo approach. Using an ensemble fitting technique, we find that the grating resolution R exceeds 2200 (3σ lower bound). This current grating resolution meets the performance required for a notional soft X-ray grating spectroscopy mission measuring hot baryonic material in the extended halos of galaxies. Using ray-trace simulations, we identify a geometric aberration resulting from path length differences across the width of the grating as a limiting factor in assessing the resolution of these gratings and discuss methods for placing better constraints on the inherent resolution of X-ray astronomical reflection gratings fabricated using EBL. [ABSTRACT FROM AUTHOR]

Surveys have shown that up to 1/10th of all ultracool dwarfs (UCDs) are appreciable radio emitters, with their emission attributed to a combination of gyrosynchrotron radiation and the electron cyclotron maser instability. 2M J0746+2000AB is a close stellar binary comprised of an L0 and L1.5 dwarf that was previously identified as a source of 5 GHz radio emission. We used Very Long Baseline Interferometry (VLBI) to precisely track the radio emission over seven epochs in 2010–2017, and found both components to be radio emitters—the first such system identified—with the secondary component as the dominant source of emission in all epochs. The previously identified 2.07 hr periodic bursts were confirmed to originate from the secondary component, although an isolated burst was also identified from the primary component. We additionally fitted the VLBI absolute astrometric positions jointly with existing relative orbital astrometry derived from optical/infrared observations with Markov Chain Monte Carlo methods to determine the orbital parameters of the two components. We found the masses of the primary and secondary optical components to be 0.0795 ± 0.0003 M⊙, and 0.0756 ± 0.0003 M⊙, respectively, representing the most precise mass estimates of any UCDs to date. Finally, we place a 3σ upper limit of 0.9 Mjup au on the mass and separation of planets orbiting either of the two components. [ABSTRACT FROM AUTHOR]

The spin distribution of massive black holes (MBHs) contains rich information on their assembly history. However, only limited information can be extracted from currently available spin measurements of MBHs owing to the small sample size and large measurement uncertainties. Upcoming X-ray telescopes with improved spectral resolution and larger effective area are expected to provide new insights into the growth history of MBHs. Here we investigate, at a proof of concept level, how stringent constraints can be placed on the accretion history of MBHs by the spin measurements from future X-ray missions. We assume a toy model consisting of a two-phase accretion history composed of an initial coherent phase with a constant disk orientation, followed by a chaotic phase with random disk orientations in each accretion episode. By utilizing mock spin data generated from such models and performing Bayesian Markov Chain Monte Carlo simulations, we find that most accretion models of MBHs can be reconstructed provided that MBH spins are measured with an accuracy of. We also quantify the precision of the reconstructed parameters by adopting various combinations of sample sizes and spin accuracies, and find that the sample size is more crucial to model reconstruction once the spin accuracy reaches ∼0.1. To some extent, a better spin accuracy will compensate for a small sample size and vice versa. Future X-ray missions such as the Advanced Telescope for High Energy Astrophysics and the enhanced X-ray Timing and Polarimetry mission, may provide spin measurements of ≳100 MBHs with an uncertainty of ∼0.04–0.1 and will thus put strong constraints on the MBH growth history. [ABSTRACT FROM AUTHOR]

After hydrogen, oxygen, and carbon, nitrogen is one of the most chemically active species in the interstellar medium. Nitrogen-bearing molecules are very important as they are actively involved in the formation of biomolecules. Therefore, it is essential to look for nitrogen-bearing species in various astrophysical sources, specifically around high-mass star-forming regions where the evolutionary history is comparatively poorly understood. In this paper, we report on the observation of three potential prebiotic molecules, namely, isocyanic acid (HNCO), formamide (NH2CHO), and methyl isocyanate (CH3NCO), which contain peptide-like bonds (–NH–C(=O)–) in a hot molecular core, G10.47 + 0.03 (hereafter, G10). Along with the identification of these three complex nitrogen-bearing species, we speculate on their spatial distribution in the source and discuss their possible formation pathways under such conditions. A rotational diagram method under local thermodynamic equilibrium has been employed to estimate the excitation temperature and the column density of the observed species. The Markov Chain Monte Carlo method was used to obtain the best-suited physical parameters of G10 as well as line properties of some species. We also determined the hydrogen column density and the optical depth for a different continuum observed in various frequency ranges. Finally, based on these observational results, we have constructed a chemical model to explain the observational findings. We found that HNCO, NH2CHO, and CH3NCO are chemically linked with each other. [ABSTRACT FROM AUTHOR]