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<jats:title>Abstract</jats:title> <jats:p>This paper is the second in a series aimed at examining the gaseous environments of <jats:italic>z</jats:italic> ≤ 0.3 quasars and ultraluminous infrared galaxies (ULIRGs) as a function of AGN/host galaxy properties across the merger sequence. This second paper focuses on the Ly<jats:italic>α</jats:italic> emission and O <jats:sc>vi</jats:sc> 1032, 1038 and N <jats:sc>v</jats:sc> 1238, 1243 absorption features, tracers of highly ionized gas outflows, in ULIRGs observed with HST/COS. Ly<jats:italic>α</jats:italic> emission is detected in 15 out of 19 ULIRGs, and 12 of the 14 clear Ly<jats:italic>α</jats:italic> detections show emission with blueshifted velocity centroids and/or wings. The equivalent widths of the Ly<jats:italic>α</jats:italic> emission increase with increasing AGN luminosities and AGN bolometric fractions. The blueshifts of the Ly<jats:italic>α</jats:italic> emission correlate positively with those of the [O <jats:sc>iii</jats:sc>] <jats:italic>λ</jats:italic>5007 emission, where the latter traces the ionized gas outflows. The Ly<jats:italic>α</jats:italic> escape fractions tend to be slightly larger in objects with stronger AGN and larger outflow velocities, but they do not correlate with nebular line reddening. Among the 12 ULIRGs with good continuum signal-to-noise ratios, O <jats:sc>vi</jats:sc> and/or N <jats:sc>v</jats:sc> absorption features are robustly detected in six of them, all of which are blueshifted, indicative of outflows. In the combined ULIRG + quasar sample, the outflows are more frequently detected in the X-ray weak or absorbed sources. The absorption equivalent widths, velocities, and velocity dispersions of the outflows are also higher in the X-ray weak sources. No other strong correlations are visible between the properties of the outflows and those of the AGN or host galaxies.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>We present in this paper the results of high spectral resolution (<jats:italic>R</jats:italic> = 88,100) spectroscopy at 4.7 <jats:italic>μ</jats:italic>m with iSHELL/IRTF of hot molecular gas close to the massive binary protostar W3 IRS 5. The binary was spatially resolved, and the spectra of the two sources (MIR1 and MIR2) were obtained simultaneously for the first time. Hundreds of <jats:sup>12</jats:sup>CO <jats:italic>ν</jats:italic> = 0–1, <jats:italic>ν</jats:italic> = 1–2 lines, and <jats:italic>ν</jats:italic> = 0–1 transitions of the isotopes of <jats:sup>12</jats:sup>CO were detected in absorption and are blueshifted compared to the cloud velocity <jats:italic>v</jats:italic> <jats:sub>LSR</jats:sub> = −38 km s<jats:sup>−1</jats:sup>. We decompose and identify kinematic components from the velocity profiles and apply rotation diagram and curve-of-growth analyses to determine their physical properties. The temperatures and column densities of the identified components range from 30 to 700 K and 10<jats:sup>21</jats:sup> to 10<jats:sup>22</jats:sup> cm<jats:sup>−2</jats:sup>, respectively. Our curve-of-growth analyses consider two scenarios. One assumes a foreground slab with a partial covering factor, which well reproduces the absorption of most of the components. The other assumes a circumstellar disk with an outward-decreasing temperature in the vertical direction and reproduces the absorption of all of the hot components. We attribute the physical origins of the identified components to the foreground envelope (&lt;100 K), post-J-shock regions (200–300 K), and clumpy structures on the circumstellar disks (∼600 K). We propose that the components with a J-shock origin are akin to water maser spots in the same region and complement the physical information of water masers along the direction of their movements.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Global hydrodynamic simulations of internal solar dynamics have focused on replicating the conditions for solar-like (equator rotating faster than the poles) differential rotation and meridional circulation using the results of helioseismic inversions as a constraint. Inferences of meridional circulation, however, have provided controversial results showing the possibility of one, two, or multiple cells along the radius. To help address this controversy and develop a more robust understanding of global flow regimes in the solar interior, we apply a “forward-modeling” approach to the analysis of helioseismic signatures of meridional circulation profiles obtained from numerical simulations. We employ the global acoustic modeling code GALE to simulate the propagation of acoustic waves through regimes of mean mass-flows generated by global hydrodynamic and magnetohydrodynamic models: EULAG, the Pencil code, and the Rayleigh code. These models are used to create synthetic Dopplergram data products, used as inputs for local time–distance helioseismology techniques. Helioseismic travel-time signals from solutions obtained through global numerical simulations are compared directly with inferences from solar observations, in order to set additional constraints on global model parameters in a direct way. We show that even though these models are able to replicate solar-like differential rotation, the resulting rotationally constrained convection develops a multicell global meridional circulation profile that is measurably inconsistent with local time–distance inferences of solar observations. However, we find that the development of rotationally unconstrained convection close to the model surface is able to maintain solar-like differential rotation, while having a significant impact on the helioseismic travel-time signal, replicating solar observations within one standard deviation of the error due to noise.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>The sharpest optical images of the R136 cluster in the Large Magellanic Cloud are presented, allowing us for the first time to resolve members of the central core, including R136a1, the most-massive star known. These data were taken using the Gemini speckle imager Zorro in medium-band filters with effective wavelengths similar to <jats:italic>BVRI</jats:italic> achieving angular resolutions between 30–40 mas. All stars previously known in the literature, having <jats:italic>V</jats:italic> &lt; 16 mag within the central 2″ × 2″, were recovered. Visual companions (≥40 mas; 2000 au) were detected for the WN5h stars R136 a1 and a3. Photometry of the visual companion of a1 suggests it is of mid-O spectral type. Based on new photometric luminosities using the resolved Zorro imaging, the masses of the individual WN5h stars are estimated to be between 150 and 200 <jats:italic>M</jats:italic> <jats:sub>⊙</jats:sub>, lowering significantly the present-day masses of some of the most-massive stars known. These mass estimates are critical anchor points for establishing the stellar upper-mass function.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>We present Atacama Large Millimeter/submillimeter Array (ALMA) Cycle 2 observations of CO(2–1) emission from the circumnuclear disks in two early-type galaxies, NGC 1380 and NGC 6861. The disk in each galaxy is highly inclined (<jats:italic>i</jats:italic> ∼ 75°), and the projected velocities of the molecular gas near the galaxy centers are ∼300 km s<jats:sup>−1</jats:sup> in NGC 1380 and ∼500 km s<jats:sup>−1</jats:sup> in NGC 6861. We fit thin disk dynamical models to the ALMA data cubes to constrain the masses of the central black holes (BHs). We created host galaxy models using Hubble Space Telescope images for the extended stellar mass distributions and incorporated a range of plausible central dust extinction values. For NGC 1380, our best-fit model yields <jats:italic>M</jats:italic> <jats:sub>BH</jats:sub> = 1.47 × 10<jats:sup>8</jats:sup> <jats:italic>M</jats:italic> <jats:sub>⊙</jats:sub> with a ∼40% uncertainty. For NGC 6861, the lack of dynamical tracers within the BH’s sphere of influence due to a central hole in the gas distribution precludes a precise measurement of <jats:italic>M</jats:italic> <jats:sub>BH</jats:sub>. However, our model fits require a value for <jats:italic>M</jats:italic> <jats:sub>BH</jats:sub> in the range of (1–3) × 10<jats:sup>9</jats:sup> <jats:italic>M</jats:italic> <jats:sub>⊙</jats:sub> in NGC 6861 to reproduce the observations. The BH masses are generally consistent with predictions from local BH–host galaxy scaling relations. Systematic uncertainties associated with dust extinction of the host galaxy light and choice of host galaxy mass model dominate the error budget of both measurements. Despite these limitations, the measurements demonstrate ALMA’s ability to provide constraints on BH masses in cases where the BH’s projected radius of influence is marginally resolved or the gas distribution has a central hole.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>We present a broadband X-ray study of W50 (the “Manatee” nebula), the complex region powered by the microquasar SS 433, that provides a test bed for several important astrophysical processes. The W50 nebula, a Galactic PeVatron candidate, is classified as a supernova remnant but has an unusual double-lobed morphology likely associated with the jets from SS 433. Using NuSTAR, XMM-Newton, and Chandra observations of the inner eastern lobe of W50, we have detected hard nonthermal X-ray emission up to ∼30 keV, originating from a few-arcminute-sized knotty region (“Head”) located ≲18′ (29 pc for a distance of 5.5 kpc) east of SS 433, and constrained its photon index to 1.58 ± 0.05 (0.5–30 keV band). The index gradually steepens eastward out to the radio “ear” where thermal soft X-ray emission with a temperature <jats:italic>kT</jats:italic> ∼ 0.2 keV dominates. The hard X-ray knots mark the location of acceleration sites within the jet and require an equipartition magnetic field of the order of ≳12 <jats:italic>μ</jats:italic>G. The unusually hard spectral index from the “Head” region challenges classical particle acceleration processes and points to particle injection and reacceleration in the subrelativistic SS 433 jet, as seen in blazars and pulsar wind nebulae.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>We have investigated the protostellar disk around a Class 0/I protostar, L1527 IRS, using multiwavelength observations of the dust continuum emission at <jats:italic>λ</jats:italic> = 0.87, 2.1, 3.3, and 6.8 mm, obtained by the Atacama Large Millimeter/submillimeter Array and the Jansky Very Large Array (VLA). Our observations achieved a spatial resolution of 3–13 au and revealed an edge-on disk structure with a size of ∼80–100 au. The emission at 0.87 and 2.1 mm is found to be optically thick, within a projected disk radius of <jats:italic>r</jats:italic> <jats:sub>proj</jats:sub> ≲ 50 au. The emission at 3.3 and 6.8 mm shows that the power-law index of the dust opacity (<jats:italic>β</jats:italic>) is <jats:italic>β</jats:italic> ∼ 1.7 around <jats:italic>r</jats:italic> <jats:sub>proj</jats:sub> ∼ 50 au, suggesting that grain growth has not yet begun. The dust temperature (<jats:italic>T</jats:italic> <jats:sub>dust</jats:sub>) shows a steep decrease with <jats:italic>T</jats:italic> <jats:sub>dust</jats:sub> ∝ <jats:italic>r</jats:italic> <jats:sub>proj</jats:sub> <jats:sup>−2</jats:sup> outside the VLA clumps previously identified at <jats:italic>r</jats:italic> <jats:sub>proj</jats:sub> ∼ 20 au. Furthermore, the disk is gravitationally unstable at <jats:italic>r</jats:italic> <jats:sub>proj</jats:sub> ∼ 20 au, as indicated by a Toomre <jats:italic>Q</jats:italic> parameter value of <jats:italic>Q</jats:italic> ≲ 1.0. These results suggest that the VLA clumps are formed via gravitational instability, which creates a shadow on the outside of the substructure, resulting in the sudden drop in temperature. The derived dust masses for the VLA clumps are ≳0.1 <jats:italic>M</jats:italic> <jats:sub>J</jats:sub>. Thus, we suggest that Class 0/I disks can be massive enough to be gravitationally unstable, which may be the origin of gas giant planets in a 20 au radius. Furthermore, the protostellar disks could be cold due to shadowing.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Previous studies have suggested that the Kelvin–Helmholtz instability (KHI) and magnetohydrodynamic (MHD) wave emissions via the KHI along various shear flow boundaries in a solar–terrestrial environment may be possible. We expand upon these previous studies to investigate the linear and nonlinear evolution of the KHI and emission of MHD waves along the boundaries of coronal mass ejections (CMEs). Our results demonstrate that the KHI and MHD wave emission due to the KHI are possible along the CME boundaries during the KHI development. We found that magnetic field orientation in the region outside of the CME has strong effects on the strength of MHD wave emission. While a smaller parallel component of the magnetic field resulted in larger growth rates in the KHI development, a larger parallel component of the magnetic field resulted in stronger MHD wave emissions. For all cases we investigated, we identified emitted waves to be fast MHD waves. We suggest that these emitted MHD waves may be able to carry available kinetic energy from the CME flow to the outside of the CME, thereby contributing to solar coronal heating via energy dissipation.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>For several decades, the origin of ultra-high-energy cosmic rays (UHECRs) has been an unsolved question of high-energy astrophysics. One approach for solving this puzzle is to correlate UHECRs with high-energy neutrinos, since neutrinos are a direct probe of hadronic interactions of cosmic rays and are not deflected by magnetic fields. In this paper, we present three different approaches for correlating the arrival directions of neutrinos with the arrival directions of UHECRs. The neutrino data are provided by the IceCube Neutrino Observatory and ANTARES, while the UHECR data with energies above ∼50 EeV are provided by the Pierre Auger Observatory and the Telescope Array. All experiments provide increased statistics and improved reconstructions with respect to our previous results reported in 2015. The first analysis uses a high-statistics neutrino sample optimized for point-source searches to search for excesses of neutrino clustering in the vicinity of UHECR directions. The second analysis searches for an excess of UHECRs in the direction of the highest-energy neutrinos. The third analysis searches for an excess of pairs of UHECRs and highest-energy neutrinos on different angular scales. None of the analyses have found a significant excess, and previously reported overfluctuations are reduced in significance. Based on these results, we further constrain the neutrino flux spatially correlated with UHECRs.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>We have performed a high-resolution 4–13 <jats:italic>μ</jats:italic>m spectral survey of the hot molecular gas associated with the massive protostars AFGL 2591 and AFGL 2136. Here we present the results of the analysis of the <jats:italic>ν</jats:italic> <jats:sub>2</jats:sub> band of H<jats:sub>2</jats:sub>O, detected with the Echelon Cross Echelle Spectrograph on board the Stratospheric Observatory for Infrared Astronomy between wavelengths of 5 and 8 <jats:italic>μ</jats:italic>m. All lines are seen in absorption. Rotation diagrams indicate that the gas is optically thick and lines are observed to saturate at 40% and 15% relative to the continuum for AFGL 2136 and AFGL 2591, respectively. We applied two curve of growth analyses to derive the physical conditions, one assuming a foreground origin and one a circumstellar disk origin. We find temperatures of 400–600 K. A foreground origin would require the presence of externally heated clumps that are smaller than the continuum source. The disk analysis is based on stellar atmosphere theory, which takes into consideration the temperature gradient in the disk. We discuss the challenges with each model, taking into consideration the properties of other species detected in the spectral survey, and conclude that further modeling efforts are required to establish whether the absorption has a disk or foreground origin. The main challenge to the foreground model is that molecules are expected to be observed in emission. The main challenges to the disk model are the midplane heating mechanism and the presence of narrow absorption lines shifted from the systemic velocity.</jats:p>