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<jats:title>Abstract</jats:title> <jats:p>We present [C <jats:sc>ii</jats:sc>] 158 <jats:italic>μ</jats:italic>m and [O <jats:sc>i</jats:sc>] 63 <jats:italic>μ</jats:italic>m observations of the bipolar H <jats:sc>ii</jats:sc> region RCW 36 in the Vela C molecular cloud, obtained within the SOFIA legacy project FEEDBACK, which is complemented with APEX <jats:sup>12/13</jats:sup>CO (3–2) and Chandra X-ray (0.5–7 keV) data. This shows that the molecular ring, forming the waist of the bipolar nebula, expands with a velocity of 1–1.9 km s<jats:sup>−1</jats:sup>. We also observe an increased line width in the ring, indicating that turbulence is driven by energy injection from the stellar feedback. The bipolar cavity hosts blueshifted expanding [C <jats:sc>ii</jats:sc>] shells at 5.2 ± 0.5 ± 0.5 km s<jats:sup>−1</jats:sup> (statistical and systematic uncertainty), which indicates that expansion out of the dense gas happens nonuniformly and that the observed bipolar phase might be relatively short (∼0.2 Myr). The X-ray observations show diffuse emission that traces a hot plasma, created by stellar winds, in and around RCW 36. At least 50% of the stellar wind energy is missing in RCW 36. This is likely due to leakage that is clearing even larger cavities around the bipolar RCW 36 region. Lastly, the cavities host high-velocity wings in [C <jats:sc>ii</jats:sc>], which indicates relatively high mass ejection rates (∼5 × 10<jats:sup>−4</jats:sup> <jats:italic>M</jats:italic> <jats:sub>⊙</jats:sub> yr<jats:sup>−1</jats:sup>). This could be driven by stellar winds and/or radiation but remains difficult to constrain. This local mass ejection, which can remove all mass within 1 pc of RCW 36 in 1–2 Myr, and the large-scale clearing of ambient gas in the Vela C cloud indicate that stellar feedback plays a significant role in suppressing the star formation efficiency.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Arcus is a proposed Explorer Class soft X-ray grating spectrometer. It aims to explore cosmic feedback by mapping hot gases within and between galaxies and galaxy clusters and characterizing jets and winds from supermassive black holes and to investigate the dynamics of protoplanetary disks and stellar accretion. Arcus features 12 m focal-length grazing-incidence silicon pore optics (SPO) developed for the Athena mission. Critical-angle transmission (CAT) gratings efficiently disperse high diffraction orders onto CCDs. We report new and improved X-ray performance results for Arcus-like CAT gratings, including a record resolving power for two coaligned CAT gratings. Multiple Arcus prototype grating facets were illuminated by an SPO at the PANTER facility. The facets consist of 32 × 32.5 mm<jats:sup>2</jats:sup> patterned silicon membranes, bonded to metal frames. The bonding angle is adjusted according to the measured average tilt angle of the grating bars in the membrane. Two simultaneously illuminated facets show a minor broadening of the Al-K<jats:sub> <jats:italic>α</jats:italic> </jats:sub> doublet in the 18th and 21st orders with the best-fit record effective resolving power of <jats:inline-formula> <jats:tex-math> <?CDATA ${R}_{G}\approx {1.3}_{-0.5}^{+\infty }\times {10}^{4}$?> </jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msub> <mml:mrow> <mml:mi>R</mml:mi> </mml:mrow> <mml:mrow> <mml:mi>G</mml:mi> </mml:mrow> </mml:msub> <mml:mo>≈</mml:mo> <mml:msubsup> <mml:mrow> <mml:mn>1.3</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>−</mml:mo> <mml:mn>0.5</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>+</mml:mo> <mml:mo>∞</mml:mo> </mml:mrow> </mml:msubsup> <mml:mo>×</mml:mo> <mml:msup> <mml:mrow> <mml:mn>10</mml:mn> </mml:mrow> <mml:mrow> <mml:mn>4</mml:mn> </mml:mrow> </mml:msup> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjac7a3aieqn1.gif" xlink:type="simple" /> </jats:inline-formula> (3<jats:italic>σ</jats:italic>), about three to four times the Arcus requirement. We measured the diffraction efficiency of quasi-fully illuminated gratings at O-K wavelengths in orders 4–7 in an Arcus-like configuration and compare results with synchrotron spot measurements. After corrections for geometrical effects and bremsstrahlung continuum, we find agreement between full and spot illumination at the two different facilities, as well as with the models used for Arcus effective area predictions. We find that these flight-like gratings meet the diffraction efficiency and greatly exceed the resolving power Arcus requires.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>We present observations of recurrent active region coronal jets, and derive their thermal and non-thermal properties, by studying the physical properties of the plasma simultaneously at the base footpoint and along the outflow of jets. The sample of analyzed solar jets were observed by SDO-AIA in extreme ultraviolet and by RHESSI in the X-ray domain. The main thermal plasma physical parameters, such as temperature, density, energy flux contributions, etc., are calculated using multiple inversion techniques to obtain the differential emission measure from extreme-ultraviolet filtergrams. The underlying models are assessed, and their limitations and applicability are scrutinized. Complementarily, we perform source reconstruction and spectral analysis of higher energy X-ray observations to further assess the thermal structure and identify non-thermal plasma emission properties. We discuss a peculiar penumbral magnetic reconnection site, which we previously identified as a “Coronal Geyser.” Evidence supporting cool and hot thermal emission, as well as non-thermal emission, is presented for a subset of geyser jets. These active region jets are found to be energetically stronger than their polar counterparts, but we find their potential influence on heliospheric energetics and dynamics to be limited. We scrutinize whether the geyser does fit the non-thermal erupting microflare picture, finding that our observations at peak flaring times can only be explained by a combination of thermal and non-thermal emission models. This analysis of geysers provides new information and observational constraints applicable to theoretical modeling of solar jets.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>In the era of large-scale spectroscopic surveys in the Local Group, we can explore using chemical abundances of halo stars to study the star formation and chemical enrichment histories of the dwarf galaxy progenitors of the Milky Way (MW) and M31 stellar halos. In this paper, we investigate using the chemical abundance ratio distributions (CARDs) of seven stellar halos from the Latte suite of FIRE-2 simulations. We attempt to infer galaxies’ assembly histories by modeling the CARDs of the stellar halos of the Latte galaxies as a linear combination of <jats:italic>template</jats:italic> CARDs from disrupted dwarfs, with different stellar masses <jats:italic>M</jats:italic> <jats:sub>⋆</jats:sub> and quenching times <jats:italic>t</jats:italic> <jats:sub>100</jats:sub>. We present a method for constructing these templates using present-day dwarf galaxies. For four of the seven Latte halos studied in this work, we recover the mass spectrum of accreted dwarfs to a precision of &lt;10%. For the fraction of mass accreted as a function of <jats:italic>t</jats:italic> <jats:sub>100</jats:sub>, we find the residuals of 20%–30% for five of the seven simulations. We discuss the failure modes of this method, which arise from the diversity of star formation and chemical enrichment histories that dwarf galaxies can take. These failure cases can be robustly identified by the high model residuals. Although the CARDs modeling method does not successfully infer the assembly histories in these cases, the CARDs of these disrupted dwarfs contain signatures of their unusual formation histories. Our results are promising for using CARDs to learn more about the histories of the progenitors of the MW and M31 stellar halos.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>We present the spatially resolved absolute brightness of the Fe <jats:sc>x</jats:sc>, Fe <jats:sc>xi</jats:sc>, and Fe <jats:sc>xiv</jats:sc> visible coronal emission lines from 1.08 to 3.4 <jats:italic>R</jats:italic> <jats:sub>⊙</jats:sub>, observed during the 2019 July 2 total solar eclipse (TSE). The morphology of the corona was typical of solar minimum, with a dipole field dominance showcased by large polar coronal holes and a broad equatorial streamer belt. The Fe <jats:sc>xi</jats:sc> line is found to be the brightest, followed by Fe <jats:sc>x</jats:sc> and Fe <jats:sc>xiv</jats:sc> (in disk <jats:italic>B</jats:italic> <jats:sub>⊙</jats:sub> units). All lines had brightness variations between streamers and coronal holes, where Fe <jats:sc>xiv</jats:sc> exhibited the largest variation. However, Fe <jats:sc>x</jats:sc> remained surprisingly uniform with latitude. The Fe line brightnesses are used to infer the relative ionic abundances and line-of-sight-averaged electron temperature (<jats:italic>T</jats:italic> <jats:sub> <jats:italic>e</jats:italic> </jats:sub>) throughout the corona, yielding values from 1.25 to 1.4 MK in coronal holes and up to 1.65 MK in the core of streamers. The line brightnesses and inferred <jats:italic>T</jats:italic> <jats:sub> <jats:italic>e</jats:italic> </jats:sub> values are then quantitatively compared to the Predictive Science Inc. magnetohydrodynamic model prediction for this TSE. The MHD model predicted the Fe lines rather well in general, while the forward-modeled line ratios slightly underestimated the observationally inferred <jats:italic>T</jats:italic> <jats:sub> <jats:italic>e</jats:italic> </jats:sub> within 5%–10% averaged over the entire corona. Larger discrepancies in the polar coronal holes may point to insufficient heating and/or other limitations in the approach. These comparisons highlight the importance of TSE observations for constraining models of the corona and solar wind formation.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>We compare the CO(1–0) and H<jats:italic>α</jats:italic> kinematics in 34 nearby galaxies, selected from the ALMaQUEST and EDGE-CALIFA surveys. We use 3D-Barolo, a 3D tilted-ring model, to derive the CO and H<jats:italic>α</jats:italic> rotation curves. Before comparing rotation curves in the 34 nearby galaxies, we found systematics between the MaNGA and CALIFA data using eight MaNGA-CALIFA overlapping galaxies. We assume the rotation curves based on the MaNGA data are accurate and made the corresponding correction to the CALIFA data. Our result shows that ∼56% (19/34) of our galaxies present slower H<jats:italic>α</jats:italic> rotation curves compared to the CO rotation curves, with a median value of 6.5 km s<jats:sup>−1</jats:sup>. The remaining galaxies (15/34) show consistent CO–H<jats:italic>α</jats:italic> rotation velocity within uncertainties. As a result, the H<jats:italic>α</jats:italic> rotation may underestimate the total dynamical mass by 6% for a circular velocity of 200 km s<jats:sup>−1</jats:sup> (the median value in our sample). Furthermore, the difference in the velocity between the CO and H<jats:italic>α</jats:italic> rotational velocity is found to correlate with the difference in velocity dispersion between CO and H<jats:italic>α</jats:italic>, suggesting that gas pressure plays a role in the discrepancy in velocity. After incorporating the effect of pressure support due to the turbulent gas motion into our sample, the median value of the difference in the velocities decreases to 1.9 km s<jats:sup>−1</jats:sup>, which in turn reduces the underestimation of the dynamical mass to ∼2%. Finally, we also investigate the role that the extraplanar diffuse ionized gas plays in the discrepancy in the velocity of CO–H<jats:italic>α</jats:italic>.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>The recently launched James Webb Space Telescope promises unparalleled advances in our understanding of the first stars and galaxies, but realizing this potential requires cosmological simulations that capture the key physical processes that affected these objects. Here, we show that radiative transfer and subgrid turbulent mixing are two such processes. By comparing simulations with and without radiative transfer but with exactly the same physical parameters and subgrid turbulent mixing model, we show that tracking radiative transfer suppresses the Population III star formation density by a factor ≈4. In both simulations, ≳90% of Population III stars are found in the unresolved pristine regions tracked by our subgrid model, which does a better job at modeling the regions surrounding proto-galaxy cores where metals from supernovae take tens of megayears to mix thoroughly. At the same time, radiative transfer suppresses Population III star formation, via the development of ionized bubbles that slow gas accretion in these regions, and it results in compact high-redshift galaxies that are surrounded by isolated low-mass satellites. Thus, turbulent mixing and radiative transfer are both essential processes that must be included to accurately model the morphology, composition, and growth of primordial galaxies.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>We investigate the formation of molecular clouds from atomic gas by using three-dimensional magnetohydrodynamical simulations, including nonequilibrium chemical reactions, heating/cooling processes, and self-gravity by changing the collision speed <jats:italic>V</jats:italic> <jats:sub>0</jats:sub> and the angle <jats:italic>θ</jats:italic> between the magnetic field and colliding flow. We found that the efficiency of the dense-gas formation depends on <jats:italic>θ</jats:italic>. For small <jats:italic>θ</jats:italic>, anisotropic super-Alfvénic turbulence delays the formation of gravitationally unstable clumps. An increase in <jats:italic>θ</jats:italic> develops shock-amplified magnetic fields along which the gas accumulates, creating prominent filamentary structures. We further investigate the statistical properties of dense clumps identified with different density thresholds. The statistical properties of the dense clumps with lower densities depend on <jats:italic>V</jats:italic> <jats:sub>0</jats:sub> and <jats:italic>θ</jats:italic> because their properties are inherited from the global turbulence structure of molecular clouds. By contrast, denser clumps appear to have asymptotic universal statistical properties, which do not significantly depend on the properties of the colliding flow. The internal velocity dispersions approach subsonic and plasma <jats:italic>β</jats:italic> becomes order of unity. We develop an analytic formula of the virial parameter that reproduces the simulation results reasonably well. This property may be one of the reasons for the universality of the initial mass function of stars.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>The infrared (IR) excess from OB stars is commonly considered to be a contribution from ionized stellar wind or circumstellar dust. With the newly published Large Sky Area Multi-Object Fiber Spectroscopy Telescope (LAMOST)-OB catalog and Galactic O-Star Spectroscopic Survey data, this work steps further on understanding the IR excess of OB stars. Based on a forward-modeling approach comparing the spectral slope of observational spectral energy distributions and photospheric models, 1147 stars are found to have IR excess out of 7818 stars with good-quality photometric data. After removing the objects in the sightline of dark clouds, 532 (∼7%) B-type stars and 118 (∼23%) O-type stars are identified to be true OB stars with circumstellar IR excess emission. The ionized stellar wind model and the circumstellar dust model are adopted to explain the IR excess, and Bayes factors are computed to quantitatively compare the two. It is shown that the IR excess can be accounted for by the stellar wind for about 65% cases, of which 33% by free–free emission and 32% by synchrotron radiation. Other 30% sources could have and 4% should have a dust component or other mechanisms to explain the sharp increase in flux at <jats:italic>λ</jats:italic> &gt; 10 <jats:italic>μ</jats:italic>m. The parameters of the dust model indicate a large-scale circumstellar halo structure, which implies the origin of the dust from the birthplace of the OB stars. A statistical study suggests that the proportion with IR excess in OB stars increases with the stellar effective temperature and luminosity, and that there is no systematic change in the mechanism for IR emission with stellar parameters.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Recent work has shown that plots of solar flare X-ray peak temperatures, Tm, versus log peak fluxes, Fp, show statistically significant separations of lower Tm flares with fast (Vcme ≥ 1000 km s<jats:sup>−1</jats:sup>) and wide (Wcme = 360°) strong coronal mass ejections (CMEs) from higher Tm flares with no CMEs or slow (Vcme &lt; 1000 km s<jats:sup>−1</jats:sup>) or narrow (&lt;360°) weak CMEs. We extend that statistical separation to CME kinetic energies, Ecme. Flares with long-duration timescales also have well-known associations with fast CMEs and solar energetic (<jats:italic>E</jats:italic> &gt; 10 MeV) particle events. Using a data set of 585 ≥ M3.0 GOES X-ray flares, we ask whether longer flare timescales (rise times, TR; durations from onset to half-power decay, TD; decay times to half power, Td; and decay times to C2, TC2) also statistically discriminate among the three groups of CMEs for speeds, widths, and energies. All log–log plots of flare timescales versus Fp produce significant separations of the three groups of CMEs generally better than those of Tm versus log Fp. We use separations of CME distribution medians to sort the four flare timescales as effective discriminants among the three CME groups. Separations between the confined flares (no-CMEs) and weak CMEs are generally smaller than those between the weak CMEs and strong CMEs. A combination of Tm and TC2 provides optimum group separations, but Tm and log TD or log Td appears best for CME forecasting purposes.</jats:p>