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<jats:title>Abstract</jats:title> <jats:p>We report the kinematic, orbital, and chemical properties of 12 stellar streams with no evident progenitors using line-of-sight velocities and metallicities from the Southern Stellar Stream Spectroscopic Survey (<jats:italic>S</jats:italic> <jats:sup>5</jats:sup>), proper motions from Gaia EDR3, and distances derived from distance tracers or the literature. This data set provides the largest homogeneously analyzed set of streams with full 6D kinematics and metallicities. All streams have heliocentric distances between ∼10 and 50 kpc. The velocity and metallicity dispersions show that half of the stream progenitors were disrupted dwarf galaxies (DGs), while the other half originated from disrupted globular clusters (GCs), hereafter referred to as DG and GC streams. Based on the mean metallicities of the streams and the mass–metallicity relation, the luminosities of the progenitors of the DG streams range between those of Carina and Ursa Major I (−9.5 ≲ <jats:italic>M</jats:italic> <jats:sub> <jats:italic>V</jats:italic> </jats:sub> ≲ −5.5). Four of the six GC streams have mean metallicities of [Fe/H] &lt; −2, more metal poor than typical Milky Way (MW) GCs at similar distances. Interestingly, the 300S and Jet GC streams are the only streams on retrograde orbits in our dozen-stream sample. Finally, we compare the orbital properties of the streams with known DGs and GCs in the MW, finding several possible associations. Some streams appear to have been accreted with the recently discovered Gaia–Enceladus–Sausage system, and others suggest that GCs were formed in and accreted together with the progenitors of DG streams whose stellar masses are similar to those of Draco to Carina (∼10<jats:sup>5</jats:sup>–10<jats:sup>6</jats:sup> <jats:italic>M</jats:italic> <jats:sub>⊙</jats:sub>).</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Absorption-line measurements of the circumgalactic medium (CGM) display a highly nonuniform distribution of lower ionization state species accompanied by more widespread higher ionization state material. This suggests that the CGM is a dynamic, multiphase medium, such as arises in the presence of turbulence. To better understand this evolution, we perform hydrodynamic and magnetohydrodynamic (MHD) simulations of the CGM surrounding Milky Way–like galaxies. In both cases, the CGM is initially in hydrostatic balance in a 10<jats:sup>12</jats:sup> <jats:italic>M</jats:italic> <jats:sub>⊙</jats:sub> dark matter gravitational potential, and the simulations include rotation in the inner halo and turbulence that decreases radially. They also track ionizations, recombinations, and species-by-species radiative cooling in the presence of the redshift-zero UV background, employing the MAIHEM nonequilibrium chemistry package. We find that after 9 Gyr of evolution, the presence of a magnetic field leads to an overall hotter CGM, with cool gas in the center where magnetic pressure dominates. While the non-MHD run produces more cold clouds overall, we find similar Si <jats:sc>iv</jats:sc>/O <jats:sc>vi</jats:sc> and N <jats:sc>v</jats:sc>/O <jats:sc>vi</jats:sc> ratios between the MHD and non-MHD runs, which are both very different from their equilibrium values. The non-MHD halo develops cool, low angular momentum filaments above the central disk, in comparison to the MHD run that has more efficient angular momentum transport, especially for the cold gas, which forms a more ordered and extended disk late into its evolution.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>We make use of Atacama Large Millimeter/submillimeter Array continuum observations of 15 luminous Lyman-break galaxies at <jats:italic>z</jats:italic> ∼ 7–8 to probe their dust-obscured star formation. These observations are sensitive enough to probe obscured star formation rates (SFRs) of 20 <jats:italic>M</jats:italic> <jats:sub>⊙</jats:sub> yr<jats:sup>−1</jats:sup> (3<jats:italic>σ</jats:italic>). Six of the targeted galaxies show significant (≥3<jats:italic>σ</jats:italic>) dust-continuum detections, more than doubling the number of known dust-detected galaxies at <jats:italic>z</jats:italic> &gt; 6.5. Their IR luminosities range from 2.7 × 10<jats:sup>11</jats:sup> <jats:italic>L</jats:italic> <jats:sub>⊙</jats:sub> to 1.1 × 10<jats:sup>12</jats:sup> <jats:italic>L</jats:italic> <jats:sub>⊙</jats:sub>, equivalent to obscured SFRs of 25 to 101 <jats:italic>M</jats:italic> <jats:sub>⊙</jats:sub> yr<jats:sup>−1</jats:sup>. We use our results to quantify the correlation of the infrared excess (IRX) on the UV-continuum slope <jats:italic>β</jats:italic> <jats:sub>UV</jats:sub> and stellar mass. Our results are most consistent with a Small Magellanic Cloud (SMC) attenuation curve for intrinsic UV-slopes <jats:inline-formula> <jats:tex-math> <?CDATA ${\beta }_{\mathrm{UV},\mathrm{intr}}$?> </jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msub> <mml:mrow> <mml:mi>β</mml:mi> </mml:mrow> <mml:mrow> <mml:mi>UV</mml:mi> <mml:mo>,</mml:mo> <mml:mi>intr</mml:mi> </mml:mrow> </mml:msub> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjac4605ieqn1.gif" xlink:type="simple" /> </jats:inline-formula> of −2.63 and most consistent with an attenuation curve in between SMC and Calzetti for <jats:inline-formula> <jats:tex-math> <?CDATA ${\beta }_{\mathrm{UV},\mathrm{intr}}$?> </jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msub> <mml:mrow> <mml:mi>β</mml:mi> </mml:mrow> <mml:mrow> <mml:mi>UV</mml:mi> <mml:mo>,</mml:mo> <mml:mi>intr</mml:mi> </mml:mrow> </mml:msub> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjac4605ieqn2.gif" xlink:type="simple" /> </jats:inline-formula> slopes of −2.23, assuming a dust temperature <jats:italic>T</jats:italic> <jats:sub> <jats:italic>d</jats:italic> </jats:sub> of 50 K. Our fiducial IRX–stellar mass results at <jats:italic>z</jats:italic> ∼ 7–8 are consistent with marginal evolution from <jats:italic>z</jats:italic> ∼ 0. We then show how both results depend on <jats:italic>T</jats:italic> <jats:sub> <jats:italic>d</jats:italic> </jats:sub>. For our six dust-detected sources, we estimate their dust masses and find that they are consistent with dust production from supernovae if the dust destruction is low (&lt;90%). Finally we determine the contribution of dust-obscured star formation to the SFR density for UV luminous (<jats:italic>H</jats:italic>&lt;−21.5 mag: ≳1.7 <jats:italic>L</jats:italic> <jats:sup>*</jats:sup> <jats:sub>UV</jats:sub>) <jats:italic>z</jats:italic> ∼ 7–8 galaxies, finding that the total SFR density at <jats:italic>z</jats:italic> ∼ 7 and <jats:italic>z</jats:italic> ∼ 8 from bright galaxies is <jats:inline-formula> <jats:tex-math> <?CDATA ${0.20}_{-0.10}^{+0.10}$?> </jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msubsup> <mml:mrow> <mml:mn>0.20</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>−</mml:mo> <mml:mn>0.10</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>+</mml:mo> <mml:mn>0.10</mml:mn> </mml:mrow> </mml:msubsup> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjac4605ieqn3.gif" xlink:type="simple" /> </jats:inline-formula> dex and <jats:inline-formula> <jats:tex-math> <?CDATA ${0.23}_{-0.09}^{+0.06}$?> </jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msubsup> <mml:mrow> <mml:mn>0.23</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>−</mml:mo> <mml:mn>0.09</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>+</mml:mo> <mml:mn>0.06</mml:mn> </mml:mrow> </mml:msubsup> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjac4605ieqn4.gif" xlink:type="simple" /> </jats:inline-formula> dex higher, respectively; i.e., ∼<jats:inline-formula> <jats:tex-math> <?CDATA $\tfrac{1}{3}$?> </jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mstyle displaystyle="false"> <mml:mfrac> <mml:mrow> <mml:mn>1</mml:mn> </mml:mrow> <mml:mrow> <mml:mn>3</mml:mn> </mml:mrow> </mml:mfrac> </mml:mstyle> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjac4605ieqn5.gif" xlink:type="simple" /> </jats:inline-formula> of the star formation in ≳1.7 <jats:italic>L</jats:italic> <jats:sup>*</jats:sup> <jats:sub>UV</jats:sub> galaxies at <jats:italic>z</jats:italic> ∼ 7–8 is obscured by dust.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Our understanding of the properties and demographics of exoplanets critically relies on our ability to determine the fundamental properties of their host stars. The advent of Gaia and large spectroscopic surveys has now made it possible, in principle, to infer the properties of individual stars, including most exoplanet hosts, to very high precision. However, we show that, in practice, such analyses are limited by uncertainties in both the fundamental scale and our models of stellar evolution, even for stars similar to the Sun. For example, we show that current uncertainties on measured interferometric angular diameters and bolometric fluxes set a systematic uncertainty floor of ≈2.4% in temperature, ≈2.0% in luminosity, and ≈4.2% in radius. Comparisons between widely available model grids suggest uncertainties of order ≈5% in mass and ≈20% in age for main-sequence and subgiant stars. While the radius uncertainties are roughly constant over this range of stars, the model-dependent uncertainties are a complex function of luminosity, temperature, and metallicity. We provide open-source software for approximating these uncertainties for individual targets and discuss strategies for reducing these uncertainties in the future.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>The Carrington storm in 1859 September has been arguably identified as the greatest geomagnetic storm ever recorded. However, its exact magnitude and chronology remain controversial, while their source data have been derived from the Colaba <jats:italic>H</jats:italic> magnetometer in India. Here, we have located the Colaba 1859 yearbook, containing hourly measurements and spot measurements. We have reconstructed the Colaba geomagnetic disturbances in the horizontal component (Δ<jats:italic>H</jats:italic>), the eastward component (Δ<jats:italic>Y</jats:italic>), and the vertical component (Δ<jats:italic>Z</jats:italic>) around the time of the Carrington storm. On their basis, we have chronologically revised the interplanetary coronal mass ejection transit time as ≤17.1 hr and located the Δ<jats:italic>H</jats:italic> peak at 06:20—06:25 UT, revealing a magnitude discrepancy between the hourly and spot measurements (−1691 nT versus −1263 nT). Furthermore, we have newly derived the time series of Δ<jats:italic>Y</jats:italic> and Δ<jats:italic>Z</jats:italic>, which peaked at Δ<jats:italic>Y</jats:italic> ≈ 378 nT (05:50 UT) and 377 nT (06:25 UT), and Δ<jats:italic>Z</jats:italic> ≈ −173 nT (06:40 UT). We have also computed their hourly averages and removed their solar quiet field variations in each geomagnetic component to derive their hourly disturbance variations (Dist) with latitudinal weighting. Our calculations have resulted in disturbance variations with latitudinal weighting of Dist <jats:italic>Y</jats:italic> ≈ 328 nT and Dist <jats:italic>Z</jats:italic> ≈ −36 nT, and three scenarios of Dist <jats:italic>H</jats:italic> ≈ −918, −979, and −949 nT, which also approximate the minimum Dst. These data may suggest preconditioning of the geomagnetic field after the August storm (Δ<jats:italic>H</jats:italic> ≤ −570 nT), which made the September storm even more geoeffective.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Spatial inhomogeneity is one of the important features for understanding the reionization process; however, it has not yet been fully quantified. To map this inhomogeneous distribution, we simultaneously detect Ly<jats:italic>α</jats:italic> emitters (LAEs) and Lyman-break galaxies (LBGs) at <jats:italic>z</jats:italic> ∼ 6.6 from the Subaru/Hyper Suprime-Cam large-area (∼1.5 deg<jats:sup>2</jats:sup> = 34,000 cMpc<jats:sup>2</jats:sup>) deep survey. We estimate the neutral fraction, <jats:italic>x</jats:italic> <jats:sub>HI</jats:sub>, from the observed number density ratio of LAEs to LBGs, <jats:italic>n</jats:italic>(LAE)/<jats:italic>n</jats:italic>(LBG), using numerical radiative transfer simulations, in which model galaxies are selected to satisfy the observed selection function. While the average <jats:italic>x</jats:italic> <jats:sub>HI</jats:sub> within the field of view is found to be <jats:italic>x</jats:italic> <jats:sub>HI</jats:sub> &lt; 0.4, which is consistent with previous studies, the variation of <jats:italic>n</jats:italic>(LAE)/<jats:italic>n</jats:italic>(LBG) within the field of view for every 140 pMpc<jats:sup>2</jats:sup> area is found to be as large as a factor of 3. This may suggest a spatially inhomogeneous topology of reionization, but it also leaves open the possibility that the variation is based on the inherent large-scale structure of the galaxy distribution. Based on the simulations, it may be difficult to distinguish between the two from the current survey. We also find that LAEs in the high-LAE-density region are more numerous at high EW<jats:sub>0</jats:sub>, supporting the fact that the observed <jats:italic>n</jats:italic>(LAE)/<jats:italic>n</jats:italic>(LBG) is more or less driven by the neutral fraction, though the statistical significance is not high.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Working in pressureless magnetohydrodynamics, we examine the consequences of some peculiar dispersive properties of linear fast sausage modes (FSMs) in one-dimensional cylindrical equilibria with a continuous radial density profile (<jats:italic>ρ</jats:italic> <jats:sub>0</jats:sub>(<jats:italic>r</jats:italic>)). As recognized recently on solid mathematical grounds, cutoff axial wavenumbers may be absent for FSMs when <jats:italic>ρ</jats:italic> <jats:sub>0</jats:sub>(<jats:italic>r</jats:italic>) varies sufficiently slowly outside the nominal cylinder. Trapped modes may therefore exist for arbitrary axial wavenumbers and density contrasts, their axial phase speeds in the long-wavelength regime differing little from the external Alfvén speed. If these trapped modes indeed show up in the solutions to the associated initial value problem (IVP), then FSMs have a much better chance to be observed than expected with classical theory and can be invoked to account for a considerably broader range of periodicities than practiced. However, with axial fundamentals in active region loops as an example, we show that this long-wavelength expectation is not seen in our finite-difference solutions to the IVP, the reason for which is then explored by superposing the necessary eigenmodes to construct solutions to the same IVP. At least for the parameters we examine, the eigenfunctions of trapped modes are characterized by a spatial extent well exceeding the observationally reasonable range of the spatial extent of initial perturbations, meaning a negligible fraction of energy that a trapped mode can receive. We conclude that the absence of cutoff wavenumbers for FSMs in the examined equilibrium does not guarantee a distinct temporal behavior.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>High-energy cosmic rays (CRs) can be accelerated in the relativistic jets of active galactic nuclei (AGNs) powered by supermassive black holes. The baryon loading efficiency onto relativistic CR baryons from the accreting black holes is poorly constrained by observations so far. In this paper, we suggest that the <jats:italic>γ</jats:italic>-ray emission of galaxy clusters can be used to study the baryon loading factor of AGN jets, since CRs injected by AGN jets are completely confined in the galaxy clusters and sufficiently interact with the intracluster medium via a hadronic process, producing diffuse <jats:italic>γ</jats:italic>-rays. We study the propagation of CRs in the galaxy clusters and calculate the radial distribution of the <jats:italic>γ-</jats:italic>rays in the galaxy cluster with different injection rates from AGNs. By comparison with the <jats:italic>γ</jats:italic>-ray flux and upper limits of the Coma cluster measured by Fermi-LAT and VERITAS, we find the upper limit of the average baryon loading factor (defined as the efficiency with which the gravitational energy is converted into relativistic particles) to be <jats:italic>η</jats:italic> <jats:sub> <jats:italic>p</jats:italic>,grav</jats:sub> &lt; 0.1. The upper limit is much lower than that required to account for diffuse neutrino flux in the conventional blazar models.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>For the first time, we simulate the detailed spectral line emission from a solar active region (AR) with the Alfvén Wave Solar Model (AWSoM). We select an AR appearing near disk center on 2018 July 13 and use the National Solar Observatory’s Helioseismic and Magnetic Imager synoptic magnetogram to specify the magnetic field at the model’s inner boundary. To resolve small-scale magnetic features, we apply adaptive mesh refinement with a horizontal spatial resolution of 0°.35 (4.5 Mm), four times higher than the background corona. We then apply the SPECTRUM code, using CHIANTI spectral emissivities, to calculate spectral lines forming at temperatures ranging from 0.5 to 3 MK. Comparisons are made between the simulated line intensities and those observed by Hinode/Extreme-ultraviolet Imaging Spectrometer where we find close agreement across a wide range of loop sizes and temperatures (about 20% relative error for both the loop top and footpoints at a temperature of about 1.5 MK). We also simulate and compare Doppler velocities and find that simulated flow patterns are of comparable magnitude to what is observed. Our results demonstrate the broad applicability of the low-frequency AWSoM for explaining the heating of coronal loops.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Although observations of high-redshift quasars demonstrate that many supermassive black holes (BHs) reached large masses within one billion years after the Big Bang, the origin of the first BHs is still a mystery. A promising way to constrain the origin of the first BHs is to explore the average properties of <jats:italic>z</jats:italic> ≳ 6 BHs. However, typical BHs remain hidden from X-ray surveys, which is due to their relatively faint nature and the limited sensitivity of X-ray telescopes. Gravitational lensing provides an attractive way to study this unique galaxy population as it magnifies the faint light from these high-redshift galaxies. Here, we study the X-ray emission originating from 155 gravitationally lensed <jats:italic>z</jats:italic> ≳ 6 galaxies that were detected in the Reionization Lensing Cluster Survey. We utilize Chandra X-ray observations to search for active galactic nuclei (AGNs) in the individual galaxies and in the stacked galaxy samples. We did not identify an individual X-ray source that was undoubtedly associated with a high-redshift galaxy. We stack the signal from all galaxies and do not find a statistically significant detection. We split our sample based on stellar mass, star formation rate, and lensing magnification and stack these subsamples. We obtain a 2.2<jats:italic>σ</jats:italic> detection for massive galaxies with an X-ray luminosity of (3.7 ± 1.6) × 10<jats:sup>42</jats:sup> erg s<jats:sup>−1</jats:sup>, which corresponds to a (3.0 ± 1.3) × 10<jats:sup>5</jats:sup> <jats:italic>M</jats:italic> <jats:sub>⊙</jats:sub> BH accreting at its Eddington rate. Other stacks remain undetected and we place upper limits on the AGN emission. These limits imply that the bulk of BHs at <jats:italic>z</jats:italic> ≳ 6 either accrete at a few percent of their Eddington rate and/or are 1–2 orders of magnitude less massive than expected based on the stellar mass of their host galaxy.</jats:p>