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<jats:title>Abstract</jats:title> <jats:p>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 <jats:sc>i</jats:sc> K<jats:italic>α</jats:italic> line (6.0–6.4 keV), and the redshifted Fe <jats:sc>xxv</jats:sc> 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 &lt;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 <jats:sc>i</jats:sc> K<jats:italic>α</jats:italic> 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.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>We present measurements of [Fe/H] and [<jats:italic>α</jats:italic>/Fe] for 128 individual red giant branch stars (RGB) in the stellar halo of M31, including its Giant Stellar Stream (GSS), obtained using spectral synthesis of low- and medium-resolution Keck/DEIMOS spectroscopy (<jats:inline-formula> <jats:tex-math> <?CDATA $R\sim 3000$?> </jats:tex-math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjabb474ieqn1.gif" xlink:type="simple" /> </jats:inline-formula> and 6000, respectively). We observed four fields in M31's stellar halo (at projected radii of 9, 18, 23, and 31 kpc), as well as two fields in the GSS (at 33 kpc). In combination with existing literature measurements, we have increased the sample size of [Fe/H] and [<jats:italic>α</jats:italic>/Fe] measurements from 101 to a total of 229 individual M31 RGB stars. From this sample, we investigate the chemical abundance properties of M31's inner halo, finding <jats:inline-formula> <jats:tex-math> <?CDATA $\langle [\mathrm{Fe}/{\rm{H}}]\rangle =-1.08\pm 0.04$?> </jats:tex-math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjabb474ieqn2.gif" xlink:type="simple" /> </jats:inline-formula> and <jats:inline-formula> <jats:tex-math> <?CDATA $\langle [\alpha /\mathrm{Fe}]\rangle =0.40\pm 0.03$?> </jats:tex-math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjabb474ieqn3.gif" xlink:type="simple" /> </jats:inline-formula>. Between 8 and 34 kpc, the inner halo has a steep [Fe/H] gradient (−0.025 ± 0.002 dex kpc<jats:sup>−1</jats:sup>) and negligible [<jats:italic>α</jats:italic>/Fe] gradient, where substructure in the inner halo is systematically more metal-rich than the smooth component of the halo at a given projected distance. Although the chemical abundances of the inner stellar halo are largely inconsistent with that of present-day dwarf spheroidal (dSph) satellite galaxies of M31, we identified 22 RGB stars kinematically associated with the smooth component of the stellar halo that have chemical abundance patterns similar to M31 dSphs. We discuss formation scenarios for M31's halo, concluding that these dSph-like stars may have been accreted from galaxies of similar stellar mass and star formation history, or of higher stellar mass and similar star formation efficiency.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>The cosmic thermal history, quantified by the evolution of the mean thermal energy density in the universe, is driven by the growth of structures as baryons get shock heated in collapsing dark matter halos. This process can be probed by redshift-dependent amplitudes of the thermal Sunyaev–Zeldovich (SZ) effect background. To do so, we cross-correlate eight sky intensity maps in the Planck and Infrared Astronomical Satellite missions with two million spectroscopic redshift references in the Sloan Digital Sky Surveys. This delivers snapshot spectra for the far-infrared to microwave background light as a function of redshift up to <jats:italic>z</jats:italic> ∼ 3. We decompose them into the SZ and thermal dust components. Our SZ measurements directly constrain <jats:inline-formula> <jats:tex-math> <?CDATA $\langle {{bP}}_{{\rm{e}}}\rangle $?> </jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mo stretchy="false">〈</mml:mo> <mml:msub> <mml:mrow> <mml:mi mathvariant="italic">bP</mml:mi> </mml:mrow> <mml:mrow> <mml:mi mathvariant="normal">e</mml:mi> </mml:mrow> </mml:msub> <mml:mo stretchy="false">〉</mml:mo> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjabb403ieqn1.gif" xlink:type="simple" /> </jats:inline-formula>, the halo bias-weighted mean electron pressure, up to <jats:italic>z</jats:italic> ∼ 1. This is the highest redshift achieved to date, with uncorrelated redshift bins thanks to the spectroscopic references. We detect a threefold increase in the density-weighted mean electron temperature <jats:inline-formula> <jats:tex-math> <?CDATA ${\overline{T}}_{{\rm{e}}}$?> </jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msub> <mml:mrow> <mml:mover accent="true"> <mml:mrow> <mml:mi>T</mml:mi> </mml:mrow> <mml:mrow> <mml:mo stretchy="true">¯</mml:mo> </mml:mrow> </mml:mover> </mml:mrow> <mml:mrow> <mml:mi mathvariant="normal">e</mml:mi> </mml:mrow> </mml:msub> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjabb403ieqn2.gif" xlink:type="simple" /> </jats:inline-formula> from 7 × 10<jats:sup>5</jats:sup> K at <jats:italic>z</jats:italic> = 1 to 2 × 10<jats:sup>6</jats:sup> K today. Over <jats:italic>z</jats:italic> = 1–0, we witness the build-up of nearly 70% of the present-day mean thermal energy density <jats:italic>ρ</jats:italic> <jats:sub>th</jats:sub>, with the corresponding density parameter Ω<jats:sub>th</jats:sub> reaching 1.5 × 10<jats:sup>−8</jats:sup>. We find the mass bias parameter of Planck's universal pressure profile of <jats:italic>B</jats:italic> = 1.27 (or 1 − <jats:italic>b</jats:italic> = 1/<jats:italic>B</jats:italic> = 0.79), consistent with the magnitude of nonthermal pressure in gas motion and turbulence from mass assembly. We estimate the redshift-integrated mean Compton parameter <jats:italic>y</jats:italic> ∼ 1.2 × 10<jats:sup>−6</jats:sup>, which will be tested by future spectral distortion experiments. More than half originates from the large-scale structure at <jats:italic>z</jats:italic> &lt; 1, which we detect directly.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>We introduce a generalized form of an emergent dark energy model with one degree of freedom for the dark energy sector that has the flexibility to include both the ΛCDM model as well as the Phenomenologically Emergent Dark Energy (PEDE) model proposed by Li &amp; Shafieloo as two of its special limits. The free parameter for the dark energy sector, namely Δ, has a value of 0 for the Λ case and a value of 1 for the PEDE case. Fitting the introduced parametric form to Planck cosmic microwave background (CMB) data and recent <jats:italic>H</jats:italic> <jats:sub>0</jats:sub> results from local observations of cepheids and supernovae, we show that the Δ = 0 associated with the ΛCDM model would fall out of the 4<jats:italic>σ</jats:italic> confidence limits of the derived posterior of the Δ parameter. Moreover, <jats:italic>H</jats:italic> <jats:sub>0</jats:sub> tensions with the emergent dark energy model will be alleviated and this model can satisfy the combination of Planck CMB data and local <jats:italic>H</jats:italic> <jats:sub>0</jats:sub> observations with ΔDIC = −2.88 compared with the ΛCDM model.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Massive (<jats:italic>M</jats:italic> &gt; 30 <jats:italic>M</jats:italic> <jats:sub>⊙</jats:sub>) stars exhibit luminosities that are near the Eddington limit for electron scattering, causing the increase in opacity associated with iron at <jats:inline-formula> <jats:tex-math> <?CDATA $T\,\approx 180,000\,{\rm{K}}$?> </jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mi>T</mml:mi> <mml:mspace width="0.25em" /> <mml:mo>≈</mml:mo> <mml:mn>180</mml:mn> <mml:mo>,</mml:mo> <mml:mn>000</mml:mn> <mml:mspace width="0.25em" /> <mml:mi mathvariant="normal">K</mml:mi> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjabb405ieqn1.gif" xlink:type="simple" /> </jats:inline-formula> to trigger supersonic convection in their outer envelopes. Three-dimensional radiative hydrodynamics simulations by Jiang and collaborators with the Athena++ computational tool have found order-of-magnitude density and radiative flux fluctuations in these convective regions, even at optical depths <jats:inline-formula> <jats:tex-math> <?CDATA $\gg 100$?> </jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mo>≫</mml:mo> <mml:mn>100</mml:mn> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjabb405ieqn2.gif" xlink:type="simple" /> </jats:inline-formula>. We show here that radiation can diffuse out of a parcel during the timescale of convection in these optically thick parts of the star, motivating our use of a “pseudo” Mach number to characterize both the fluctuation amplitudes and their correlations. In this first paper, we derive the impact of these fluctuations on the radiative pressure gradient needed to carry a given radiative luminosity. This implementation leads to a remarkable improvement between 1D and 3D radiative pressure gradients, and builds confidence in our path to an eventual 1D implementation of these intrinsically 3D envelopes. However, simply reducing the radiation pressure gradient is not enough to implement a new 1D model. Rather, we must also account for the impact of two other aspects of turbulent convection: the substantial pressure and the ability to transport an appreciable fraction of the luminosity, which will be addressed in upcoming works. This turbulent convection also arises in other instances where the stellar luminosity approaches the Eddington luminosity. Hence, our effort should apply to other astrophysical situations where an opacity peak arises in a near Eddington-limited, radiation pressure-dominated plasma.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>The Fe <jats:sc>i</jats:sc> spectra emitted by astrophysical sources contain information on plasma parameters such as chemical abundances and magnetic fields. However, to determine these parameters requires detailed plasma modeling, which in turn needs accurate atomic data for processes such as radiative decay and electron-impact excitation in Fe <jats:sc>i</jats:sc>. A lack of fine-structure resolved collision strengths for transitions in Fe <jats:sc>i</jats:sc> is addressed in this paper with the presentation of data obtained from a Dirac <jats:italic>R</jats:italic>-matrix calculation. The suitability of our choice of target description is shown, with our energies generally within 7% of literature values. Various <jats:italic>A</jats:italic>-values are compared with other theoretical and experimental results, and the quality of the collision strengths produced in this work demonstrated. A comparison of 300- and 1000-level close-coupling expansions is made, the latter shown to eliminate pseudoresonances in the collision strengths at electron energies between 0.5 and 1.0 Ry. Maxwell-averaged effective collision strengths are presented, and the convergence of our data is shown in the temperature range 1000–100,000 K.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Residual errors in calibration coefficients corresponding to observed cosmic microwave background (CMB) maps are an important issue when estimating a pure CMB signal. These errors in the input-foreground-contaminated CMB maps, if not properly taken into account in a component separation method, may lead to bias in the cleaned CMB map and estimated CMB angular power spectrum. But the inability to exactly determine the calibration coefficients corresponding to each observed CMB map from a multifrequency CMB experiment makes it very difficult to incorporate their exact and actual values during the component separation method. Hence, the effect of any random and residual calibration error in the cleaned CMB map and its angular power spectrum of a component separation problem can only be understood by performing detailed Monte Carlo simulations. In this paper, we investigate the impact of using input-observed CMB maps with random calibration errors on the posterior density of a cleaned CMB map and theoretical CMB angular power spectrum over large angular scales of the sky following the Gibbs Internal-Linear-Combination (ILC) method. By performing detailed Monte Carlo simulations of WMAP and Planck temperature anisotropy observations, including their estimate on calibration errors, we show that the best-fit map corresponding to the posterior maximum is minimally biased in the Gibbs ILC method by a CMB normalization bias and residual foreground bias. The residual calibration-induced error in the best-fit power spectrum causes an overall 6% increase of the net error when added in quadrature with the cosmic-variance-induced error.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>GW170817 began gravitational-wave multimessenger astronomy. However, GW170817 will not be representative of detections in the coming years because typical gravitational-wave sources will be closer the detection horizon, have larger localization regions, and (when present) will have correspondingly weaker electromagnetic emission. In its design state, the gravitational-wave detector network in the mid-2020s will consist of up to five similar-sensitivity second-generation interferometers. The instantaneous sky-coverage by the full network is nearly isotropic, in contrast to the configuration during the first three observing runs. Along with the coverage of the sky, there are also commensurate increases in the average horizon for a given binary mass. We present a realistic set of localizations for binary neutron stars and neutron star–black hole binaries, incorporating intra-network duty cycles and selection effects on the astrophysical distributions. Based on the assumption of an 80% duty cycle, and that two instruments observe a signal above the detection threshold, we anticipate a median of 28 sq. deg. for binary neutron stars, and 50–120 sq. deg. for neutron star–black hole (depending on the population assumed). These distributions have a wide spread, and the best localizations, even for networks with fewer instruments, will have localizations of 1–10 sq. deg. range. The full five instrument network reduces localization regions to a few tens of degrees at worst.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>This paper presents a new approach for the regression of the center coordinates and radius of the solar disk in H<jats:italic>α</jats:italic> solar full-disk images by using a Deep Convolutional Neural Network. We use ∼100,000 original H<jats:italic>α</jats:italic> solar full-disk images obtained from Huairou Solar Observing Station as the experimental data set. The data set includes two parts: the original image and three numeric values (center coordinates and radius). In order to deal with the uneven distribution of the solar disk position in the original image, we randomly shift the solar disk during image preprocessing. Furthermore, data augmentation is also used to increase the robustness of the model. By evaluating the model with <jats:italic>R</jats:italic>-square and relative error, the center coordinates and the radius of the solar disk are proved to be effectively regressed. The data sets we constructed and source code are available as open source on GitHub.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>A clear transition feature of galaxy quenching is identified in the multi-parameter space of stellar mass (<jats:italic>M</jats:italic> <jats:sub>*</jats:sub>), bulge-to-total mass ratio (<jats:italic>B</jats:italic>/<jats:italic>T</jats:italic> <jats:sub>m</jats:sub>), halo mass (<jats:italic>M</jats:italic> <jats:sub>h</jats:sub>) and halo-centric distance (<jats:italic>r</jats:italic>/<jats:italic>r</jats:italic> <jats:sub>180</jats:sub>). For a given halo mass, the characteristic stellar mass (<jats:inline-formula> <jats:tex-math> <?CDATA ${M}_{* ,\mathrm{ch}}$?> </jats:tex-math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjabb66cieqn1.gif" xlink:type="simple" /> </jats:inline-formula>) for the transition is about one-fifth of that of the corresponding central galaxy, and almost independent of <jats:italic>B</jats:italic>/<jats:italic>T</jats:italic> <jats:sub>m</jats:sub>. Once <jats:italic>B</jats:italic>/<jats:italic>T</jats:italic> <jats:sub>m</jats:sub> is fixed, the quenched fraction of galaxies with <jats:inline-formula> <jats:tex-math> <?CDATA ${M}_{* }\lt {M}_{* ,\mathrm{ch}}$?> </jats:tex-math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjabb66cieqn2.gif" xlink:type="simple" /> </jats:inline-formula> increases with <jats:italic>M</jats:italic> <jats:sub>h</jats:sub>, but decreases with <jats:italic>M</jats:italic> <jats:sub>*</jats:sub> in the inner part of halos (<jats:italic>r</jats:italic>/<jats:italic>r</jats:italic> <jats:sub>180</jats:sub> &lt; 0.5). In the outer part (<jats:italic>r</jats:italic>/<jats:italic>r</jats:italic> <jats:sub>180</jats:sub> &gt; 0.5), the trend with <jats:italic>M</jats:italic> <jats:sub>h</jats:sub> remains but the correlation with <jats:italic>M</jats:italic> <jats:sub>*</jats:sub> is absent or becomes positive. For galaxies above <jats:inline-formula> <jats:tex-math> <?CDATA ${M}_{* ,\mathrm{ch}}$?> </jats:tex-math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjabb66cieqn3.gif" xlink:type="simple" /> </jats:inline-formula> and with <jats:italic>B</jats:italic>/<jats:italic>T</jats:italic> <jats:sub>m</jats:sub> fixed, the quenched fraction increases with <jats:inline-formula> <jats:tex-math> <?CDATA ${M}_{* }$?> </jats:tex-math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjabb66cieqn4.gif" xlink:type="simple" /> </jats:inline-formula>, but depends only weakly on <jats:italic>M</jats:italic> <jats:sub>h</jats:sub> in both the inner and outer regions. At fixed <jats:italic>B</jats:italic>/<jats:italic>T</jats:italic> <jats:sub>m</jats:sub> and <jats:italic>M</jats:italic> <jats:sub>*</jats:sub>, the quenched fraction increases with decreasing <jats:italic>r</jats:italic>/<jats:italic>r</jats:italic> <jats:sub>180</jats:sub> for galaxies with <jats:inline-formula> <jats:tex-math> <?CDATA ${M}_{* }\lt {M}_{* ,\mathrm{ch}}$?> </jats:tex-math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjabb66cieqn5.gif" xlink:type="simple" /> </jats:inline-formula>, and depends only weakly on <jats:italic>r</jats:italic>/<jats:italic>r</jats:italic> <jats:sub>180</jats:sub> for galaxies with <jats:inline-formula> <jats:tex-math> <?CDATA ${M}_{* }\gt {M}_{* ,\mathrm{ch}}$?> </jats:tex-math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjabb66cieqn6.gif" xlink:type="simple" /> </jats:inline-formula>. Our finding provides a physically motivated way to classify galaxies in halos into two classes based on their quenching properties: an “upper class” with <jats:inline-formula> <jats:tex-math> <?CDATA ${M}_{* }\gt {M}_{* ,\mathrm{ch}}$?> </jats:tex-math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjabb66cieqn7.gif" xlink:type="simple" /> </jats:inline-formula> and a “lower class” with <jats:inline-formula> <jats:tex-math> <?CDATA ${M}_{* }\lt {M}_{* ,\mathrm{ch}}$?> </jats:tex-math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjabb66cieqn8.gif" xlink:type="simple" /> </jats:inline-formula>. Environmental quenching is important for “lower class” galaxies, while internal quenching plays the dominating role for the “upper class.”</jats:p>