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<jats:title>Abstract</jats:title> <jats:p>We have studied the density profile of a dwarf halo in the decaying dark matter (DDM) cosmology, using a new algorithm that resolves halo density profiles down to the innermost 700 pc robustly with high efficiency. Following Schwarzschild’s orbit-based method, we have also developed a simplified model to calculate the DDM halo density profiles, which agree remarkably well with those from <jats:italic>N</jats:italic>-body simulations. Both zoom-in simulations and the simplified model reveal that dark matter decay leads to the flattening of the central density and an overall reduction of the density in dwarf halos, and the underlying physics mechanisms are well illustrated by the simplified model. The slowly rising scaled rotation curves of DDM dwarf halos agree with the observations of local dwarf galaxies. Our results suggest that DDM holds great potential for resolving the small-scale problems faced by the cold dark matter model.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Since the first non-thermal reports of inverse Compton (IC) emission from the intracluster medium (ICM) of galaxy clusters at hard X-ray energies, we have yet to unambiguously confirm IC emission in observations with newer facilities. RXTE detected IC emission in one of the hottest known clusters, Abell 2163 (A2163), a massive merging cluster with a giant radio halo—the presumed source of relativistic electrons IC scattering CMB photons to X-ray energies. The cluster’s redshift (<jats:italic>z</jats:italic> ∼ 0.2) allows its thermal and non-thermal radio emission to fit the field of view of the Nuclear Spectroscopic Telescope Array (NuSTAR), permitting a deep observation capable of confirming or ruling out the RXTE report. The IC flux provides constraints on the average magnetic field strength in a cluster. To determine the global diffuse IC emission in A2163, we fit its global NuSTAR spectrum with four models: single- (1T) and two-temperature (2T), 1T+power-law component (T+IC), and multi-temperature+power law (9T+IC). Each represents different characterizations of the thermal ICM emission, with power-law components added to represent IC emission. We find that the 3–30 keV spectrum can be described by purely thermal emission, with a global average temperature of <jats:italic>kT</jats:italic> = (11.8 ± 0.2) keV. The IC flux is constrained to &lt;4.0 × 10<jats:sup>−12</jats:sup> erg s<jats:sup>−1</jats:sup> cm<jats:sup>−2</jats:sup> using the 1T+IC model and &lt;1.6 × 10<jats:sup>−12</jats:sup> erg s<jats:sup>−1</jats:sup> cm<jats:sup>−2</jats:sup> with the more physical 9T+IC model, both to 90% confidence levels. Combining these limits with 1.4 GHz diffuse radio data from the VLA, we find the average magnetic field strength to be &gt;0.22 <jats:italic>μ</jats:italic>G and &gt;0.35 <jats:italic>μ</jats:italic>G, respectively, providing the strongest constraints on these values in A2163 to date.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>We present a procedure to constrain the redshifts of obscured (<jats:inline-formula> <jats:tex-math> <?CDATA ${N}_{H}\gt {10}^{22}\,{\mathrm{cm}}^{-2}$?> </jats:tex-math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjabc9c7ieqn1.gif" xlink:type="simple" /> </jats:inline-formula>) active galactic nuclei (AGN) based on low count statistics X-ray spectra, which can be adopted when photometric and/or spectroscopic redshifts are unavailable or difficult to obtain. We selected a sample of 54 obscured AGN candidates on the basis of their X-ray hardness ratio, <jats:inline-formula> <jats:tex-math> <?CDATA ${\rm{HR}}\gt -0.1$?> </jats:tex-math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjabc9c7ieqn2.gif" xlink:type="simple" /> </jats:inline-formula>, in the Chandra deep field (∼479 ks, 335 arcmin<jats:sup>2</jats:sup>) around the <jats:italic>z</jats:italic> = 6.3 QSO SDSS J1030+0524. The sample has a median value of ≈80 net counts in the 0.5–7 keV energy band. We estimate reliable X-ray redshift solutions taking advantage of the main features in obscured AGN spectra, like the Fe 6.4 keV <jats:inline-formula> <jats:tex-math> <?CDATA ${\rm{K}}\alpha $?> </jats:tex-math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjabc9c7ieqn3.gif" xlink:type="simple" /> </jats:inline-formula> emission line, the 7.1 keV Fe absorption edge, and the photoelectric absorption cutoff. The significance of such features is investigated through spectral simulations, and the derived X-ray redshift solutions are then compared with photometric redshifts. Both photometric and X-ray redshifts are derived for 33 sources. When multiple solutions are derived by any method, we find that combining the redshift solutions of the two techniques improves the rms by a factor of 2. Using our redshift estimates (<jats:inline-formula> <jats:tex-math> <?CDATA $0.1\lesssim z\lesssim 4$?> </jats:tex-math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjabc9c7ieqn4.gif" xlink:type="simple" /> </jats:inline-formula>), we derived absorbing column densities in the range <jats:inline-formula> <jats:tex-math> <?CDATA $\sim {10}^{22}\mbox{--}{10}^{24}\,{\mathrm{cm}}^{-2}$?> </jats:tex-math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjabc9c7ieqn5.gif" xlink:type="simple" /> </jats:inline-formula> and absorption-corrected, 2–10 keV rest-frame luminosities between <jats:inline-formula> <jats:tex-math> <?CDATA $\sim {10}^{42}$?> </jats:tex-math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjabc9c7ieqn6.gif" xlink:type="simple" /> </jats:inline-formula> and 10<jats:sup>45</jats:sup> erg s<jats:sup>−1</jats:sup>, with median values of <jats:inline-formula> <jats:tex-math> <?CDATA ${N}_{H}=1.7\times {10}^{23}\,{\mathrm{cm}}^{-2}$?> </jats:tex-math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjabc9c7ieqn7.gif" xlink:type="simple" /> </jats:inline-formula> and <jats:inline-formula> <jats:tex-math> <?CDATA ${L}_{2-10\mathrm{keV}}=8.3\times {10}^{43}\,\mathrm{erg}\,{{\rm{s}}}^{-1}$?> </jats:tex-math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjabc9c7ieqn8.gif" xlink:type="simple" /> </jats:inline-formula>, respectively. Our results suggest that the adopted procedure can be applied to current and future X-ray surveys for sources detected only in X-rays or that have uncertain photometric or single-line spectroscopic redshifts.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>The mergers of binary neutron stars, as well as black hole–neutron star systems, are expected to produce an electromagnetic counterpart that can be analyzed to infer the element synthesis that occurred in these events. We investigate one source of uncertainties pertinent to lanthanide-rich outflows: the nuclear inputs to rapid neutron capture nucleosynthesis calculations. We begin by examining 32 different combinations of nuclear inputs: eight mass models, two types of spontaneous fission rates, and two types of fission daughter product distributions. We find that such nuclear physics uncertainties typically generate at least one order of magnitude uncertainty in key quantities such as the nuclear heating (one and a half orders of magnitude at 1 day post-merger), the bolometric luminosity (one order of magnitude at 5 days post-merger), and the inferred mass of material from the bolometric luminosity (factor of 8 when considering the 8–10 day region). Since particular nuclear processes are critical for determining the electromagnetic signal, we provide tables of key nuclei undergoing <jats:italic>β</jats:italic>-decay, <jats:italic>α</jats:italic>-decay, and spontaneous fission important for heating at different times, identifying decays that are common among the many nuclear input combinations.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>We measure the environmental dependence, where environment is defined by the distance to the third nearest neighbor, of multiple galaxy properties inside the Environmental COntext (ECO) catalog. We focus primarily on void galaxies, which we define as the 10% of galaxies having the lowest local density. We compare the properties of void and non-void galaxies: baryonic mass, color, fractional stellar mass growth rate (FSMGR), morphology, and gas-to-stellar-mass ratio (estimated from a combination of H <jats:sc>i</jats:sc> data and photometric gas fractions calibrated with the REsolved Spectroscopy Of a Local VolumE survey). Our void galaxies typically have lower baryonic masses than galaxies in denser environments, and they display the properties expected of a lower mass population: they have more late types, are bluer, have a higher FSMGR, and are more gas-rich. We control for baryonic mass and investigate the extent to which void galaxies are different at fixed mass. Void galaxies are bluer, more gas-rich, and more star-forming at fixed mass than non-void galaxies, which is a possible signature of galaxy assembly bias. Furthermore, we show that these trends persist even at fixed mass and morphology, and we find that voids host a distinct population of early types that are bluer and more star-forming than the typical red and quenched early types. In addition to these empirical observational results, we also present theoretical results from mock catalogs with built-in galaxy assembly bias. We show that a simple matching of galaxy properties to (sub)halo properties, such as mass and age, can recover the observed environmental trends in ECO galaxies.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>We present a systematic numerical relativity study of the dynamical ejecta, winds, and nucleosynthesis in neutron star (NS) merger remnants. Binaries with the chirp mass compatible with GW170817, different mass ratios, and five microphysical equations of state (EOSs) are simulated with an approximate neutrino transport and a subgrid model for magnetohydrodynamic turbulence up to 100 ms postmerger. Spiral density waves propagating from the NS remnant to the disk trigger a wind with mass flux ∼0.1–0.5 <jats:italic>M</jats:italic> <jats:sub>⊙</jats:sub> s<jats:sup>−1</jats:sup>, which persists for the entire simulation as long as the remnant does not collapse to a black hole. This wind has average electron fraction ≳0.3 and average velocity ∼0.1–0.17 <jats:italic>c</jats:italic> and thus is a site for the production of weak <jats:italic>r</jats:italic>-process elements (mass number <jats:italic>A</jats:italic> &lt; 195). Disks around long-lived remnants have masses ∼0.1–0.2 <jats:italic>M</jats:italic> <jats:sub>⊙</jats:sub>, temperatures peaking at ≲10 MeV near the inner edge, and a characteristic double-peak distribution in entropy resulting from shocks propagating through the disk. The dynamical and spiral-wave ejecta computed in our targeted simulations are not compatible with those inferred from AT2017gfo using two-components kilonova models. Rather, they indicate that multicomponent kilonova models including disk winds are necessary to interpret AT2017gfo. The nucleosynthesis in the combined dynamical ejecta and spiral-wave wind in the long-lived mergers of comparable mass robustly accounts for all the <jats:italic>r</jats:italic>-process peaks, from mass number ∼75 to actinides in terms of solar abundances. Total abundances are weakly dependent on the EOS, while the mass ratio affects the production of first-peak elements.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>We explore stellar population properties separately in the bulge and the disk of double-component cluster galaxies, to shed light on the formation of lenticular galaxies in dense environments. We study eight low-redshift clusters from the Sydney-AAO Multi-object Integral field Galaxy Survey, using two-dimensional photometric bulge–disk decomposition in the <jats:italic>g</jats:italic>, <jats:italic>r</jats:italic>, and <jats:italic>i</jats:italic> bands to characterize galaxies. For 192 double-component galaxies with <jats:italic>M</jats:italic> <jats:sub>*</jats:sub> &gt; 10<jats:sup>10</jats:sup> <jats:italic>M</jats:italic> <jats:sub>⊙</jats:sub>, we estimate the color, age, and metallicity of the bulge and the disk. The analysis of the <jats:italic>g</jats:italic> − <jats:italic>i</jats:italic> colors reveals that bulges are redder than their surrounding disks, with a median offset of 0.12 ± 0.02 mag, consistent with previous results. To measure mass-weighted age and metallicity, we investigate three methods: (i) one based on galaxy stellar mass weights for the two components, (ii) one based on flux weights, and (iii) one based on radial separation. The three methods agree in finding 62% of galaxies having bulges that are 2–3 times more metal-rich than the disks. Of the remaining galaxies, 7% have bulges that are more metal-poor than the disks, while for 31%, the bulge and disk metallicities are not significantly different. We observe 23% of galaxies being characterized by bulges older and 34% by bulges younger with respect to the disks. The remaining 43% of galaxies have bulges and disks with statistically indistinguishable ages. Redder bulges tend to be more metal-rich than the disks, suggesting that the redder color in bulges is due to their enhanced metallicity relative to the disks instead of differences in stellar population age.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>This work extends the computational model EULAG-MHD to include Hall magnetohydrodynamics (HMHD)—important to explore physical systems undergoing fast magnetic reconnection at the order of the ion inertial length scale. Examples include solar transients along with reconnections in magnetosphere, magnetotail, and laboratory plasmas. The paper documents the results of two distinct sets of implicit large-eddy simulations in the presence and absence of the Hall forcing term, initiated with an unidirectional sinusoidal magnetic field. The HMHD simulation while benchmarking the code also emphasizes the complexity of three-dimensional (3D) evolution over its two-dimensional counterpart. The magnetic reconnections onset significantly earlier in HMHD. Importantly, the magnetic field generated by the Hall term breaks any inherent symmetry, ultimately making the evolution 3D. The resulting 3D reconnections develop magnetic flux ropes (MFRs) and magnetic flux tubes. Projected on the reconnection plane, the ropes and tubes appear as magnetic islands, which later break into secondary islands, and finally coalesce to generate an X-type neutral point. These findings are in agreement with the theory and contemporary simulations of HMHD, and thus verify our extension of the EULAG-MHD model. The second set explores the influence of the Hall forcing on generation and ascend of an MFR from sheared magnetic arcades—a novel scenario instructive in understanding the coronal transients. The rope evolves through intermediate complex structures, ultimately breaking locally because of reconnections. Interestingly, the breakage occurs earlier in the presence of the Hall term, signifying faster dynamics leading to magnetic topology favorable for reconnections.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>We present the results of a pilot Hubble Space Telescope (HST) imaging study of the host galaxies of ten quasars from the Sloan Digital Sky Survey Reverberation Mapping (SDSS-RM) project. Probing more than an order of magnitude in black hole (BH) and stellar masses, our sample is the first statistical sample to study the BH–host correlations beyond <jats:italic>z</jats:italic> &gt; 0.3 with reliable BH masses from reverberation mapping rather than from single-epoch spectroscopy. We perform image decomposition in two HST bands (UVIS-F606W and IR-F110W) to measure host colors and estimate stellar masses using empirical relations between broadband colors and the mass-to-light ratio. The stellar masses of our targets are mostly dominated by a bulge component. The BH masses and stellar masses of our sample broadly follow the same correlations found for local RM active galactic nuclei and quiescent bulge-dominant galaxies, with no strong evidence of evolution in the <jats:inline-formula> <jats:tex-math> <?CDATA ${M}_{\mathrm{BH}}\mbox{--}{M}_{* ,\mathrm{bulge}}$?> </jats:tex-math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjabc8e6ieqn1.gif" xlink:type="simple" /> </jats:inline-formula> relation to <jats:italic>z</jats:italic> ∼ 0.6. We further compare the host light fraction from HST imaging decomposition to that estimated from spectral decomposition. We find a good correlation between the host fractions derived with both methods. However, the host fraction derived from spectral decomposition is systematically smaller than that from imaging decomposition by ∼30%, indicating different systematics in both approaches. This study paves the way for upcoming more ambitious host galaxy studies of quasars with direct RM-based BH masses at high redshift.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>We use the third catalog of blazars detected by Fermi/LAT (3LAC) and <jats:italic>γ</jats:italic>-ray narrow-line Seyfert 1 Galaxies (<jats:italic>γ</jats:italic>-NLSy1s) to study the blazar sequence and relationship between them. Our results are as follows. (i) There is a weak anticorrelation between synchrotron peak frequency and peak luminosity for both Fermi blazars and <jats:italic>γ</jats:italic>-NLSy1s, which supports the blazar sequence. However, after Doppler correction, the inverse correlation disappeared, which suggests that anticorrelation between synchrotron peak frequency and peak luminosity is affected by the beaming effect. (ii) There is a significant anticorrelation between jet kinetic power and synchrotron peak frequency for both Fermi blazars and <jats:italic>γ</jats:italic>-NLSy1s, which suggests that the <jats:italic>γ</jats:italic>-NLSy1s could fit well into the original blazar sequence. (iii) According to previous work, the relationship between synchrotron peak frequency and synchrotron curvature can be explained by statistical or stochastic acceleration mechanisms. There are significant correlations between synchrotron peak frequency and synchrotron curvature for whole sample, Fermi blazars and BL Lac objects, respectively. The slopes of the correlation are consistent with statistical acceleration. For FSRQs, LBLs, IBLs, HBLs, and <jats:italic>γ</jats:italic>-NLS1s, we also find a significant correlation, but in these cases the slopes cannot be explained by previous theoretical models. (iv) The slope of the relation between synchrotron peak frequency and synchrotron curvature in <jats:italic>γ</jats:italic>-NLS1s is larger than that of FSRQs and BL Lac objects. This result may imply that the cooling dominates over the acceleration process for FSRQs and BL Lac objects, while <jats:italic>γ</jats:italic>-NLS1s is the opposite.</jats:p>