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<jats:title>Abstract</jats:title> <jats:p>The most intense solar energetic particle events are produced by coronal mass ejections (CMEs) accompanied by intense type II radio bursts below 15 MHz. Understanding where these type II bursts are generated relative to an erupting CME would reveal important details of particle acceleration near the Sun, but the emission cannot be imaged on Earth due to distortion from its ionosphere. Here, a technique is introduced to identify the likely source location of the emission by comparing the dynamic spectrum observed from a single spacecraft against synthetic spectra made from hypothesized emitting regions within a magnetohydrodynamic (MHD) numerical simulation of the recreated CME. The radio-loud 2005 May 13 CME was chosen as a test case, with Wind/WAVES radio data being used to frame the inverse problem of finding the most likely progression of burst locations. An MHD recreation is used to create synthetic spectra for various hypothesized burst locations. A framework is developed to score these synthetic spectra by their similarity to the type II frequency profile derived from the Wind/WAVES data. Simulated areas with 4× enhanced entropy and elevated de Hoffmann–Teller velocities are found to produce synthetic spectra similar to spacecraft observations. A geometrical analysis suggests the eastern edge of the entropy-derived shock around (−30°, 0°) was emitting in the first hour of the event before falling off, and the western/southwestern edge of the shock centered around (6°, −12°) was a dominant area of radio emission for the 2 hr of simulation data out to 20 solar radii.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>We report on the gas-phase metallicity gradients of a sample of 238 star-forming galaxies at 0.6 &lt; <jats:italic>z</jats:italic> &lt; 2.6, measured through deep near-infrared Hubble Space Telescope slitless spectroscopy. The observations include 12 orbit depth Hubble/WFC3 G102 grism spectra taken as a part of the CANDELS Ly<jats:italic>α</jats:italic> Emission at Reionization (CLEAR) survey, and archival WFC3 G102+G141 grism spectra overlapping the CLEAR footprint. The majority of galaxies in this sample are consistent with having a zero or slightly positive metallicity gradient (<jats:italic>dZ</jats:italic>/<jats:italic>dR</jats:italic> ≥ 0, i.e., increasing with radius) across the full mass range probed (8.5 &lt; log <jats:italic>M</jats:italic> <jats:sub>*</jats:sub>/<jats:italic>M</jats:italic> <jats:sub>⊙</jats:sub> &lt; 10.5). We measure the intrinsic population scatter of the metallicity gradients, and show that it increases with decreasing stellar mass—consistent with previous reports in the literature, but confirmed here with a much larger sample. To understand the physical mechanisms governing this scatter, we search for correlations between the observed gradient and various stellar population properties at fixed mass. However, we find no evidence for a correlation with the galaxy properties we consider—including star formation rates, sizes, star formation rate surface densities, and star formation rates per gravitational potential energy. We use the observed weakness of these correlations to provide material constraints for predicted intrinsic correlations from theoretical models.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Precise cosmic web classification of observed galaxies in massive spectroscopic surveys can be either highly uncertain or computationally expensive. As an alternative, we explore a fast Machine Learning-based approach to infer the underlying dark matter tidal cosmic web environment of a galaxy distribution from its <jats:italic>β</jats:italic>-skeleton graph. We develop and test our methodology using the cosmological magnetohydrodynamic simulation Illustris-TNG at <jats:italic>z</jats:italic> = 0. We explore three different tree-based machine-learning algorithms to find that a random forest classifier can best use graph-based features to classify a galaxy as belonging to a peak, filament, or sheet as defined by the T-Web classification algorithm. The best match between the galaxies and the dark matter T-Web corresponds to a density field smoothed over scales of 2 Mpc, a threshold over the eigenvalues of the dimensionless tidal tensor of <jats:italic>λ</jats:italic> <jats:sub>th</jats:sub> = 0.0, and galaxy number densities around 8 × 10<jats:sup>−3</jats:sup> Mpc<jats:sup>−3</jats:sup>. This methodology results on a weighted F1 score of 0.728 and a global accuracy of 74%. More extensive tests that take into account light-cone effects and redshift space distortions are left for future work. We make one of our highest ranking random forest models available on a public repository for future reference and reuse.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Here, we report ALMA detections of polarized emission from dust, CS(<jats:italic>J</jats:italic> = 5 → 4), and C<jats:sup>33</jats:sup>S(<jats:italic>J</jats:italic> = 5 → 4) toward the high-mass star-forming region NGC 6334I(N). A clear “hourglass” magnetic field morphology was inferred from the polarized dust emission, which is also directly seen from the polarized CS emission across velocity, where the polarization appears to be parallel to the field. By considering previous findings, the field retains a pinched shape that can be traced to clump length scales from the envelope scales traced by ALMA, suggesting that the field is dynamically important across multiple length scales in this region. The CS total intensity emission is found to be optically thick (<jats:italic>τ</jats:italic> <jats:sub>CS</jats:sub> = 32 ± 12) while the C<jats:sup>33</jats:sup>S emission appears to be optically thin (<jats:inline-formula> <jats:tex-math> <?CDATA ${\tau }_{{{\rm{C}}}^{33}{\rm{S}}}=0.1\pm 0.01$?> </jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msub> <mml:mrow> <mml:mi>τ</mml:mi> </mml:mrow> <mml:mrow> <mml:msup> <mml:mrow> <mml:mi mathvariant="normal">C</mml:mi> </mml:mrow> <mml:mrow> <mml:mn>33</mml:mn> </mml:mrow> </mml:msup> <mml:mi mathvariant="normal">S</mml:mi> </mml:mrow> </mml:msub> <mml:mo>=</mml:mo> <mml:mn>0.1</mml:mn> <mml:mo>±</mml:mo> <mml:mn>0.01</mml:mn> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjac28a1ieqn1.gif" xlink:type="simple" /> </jats:inline-formula>). This suggests that sources of anisotropy other than large velocity gradients, i.e., anisotropies in the radiation field, are required to explain the polarized emission from CS seen by ALMA. By using four variants of the Davis–Chandrasekhar–Fermi technique and the angle dispersion function methods (ADF), we obtain an average of the estimates for the magnetic field strength on the plane of the sky of <jats:inline-formula> <jats:tex-math> <?CDATA $\left\langle {B}_{\mathrm{pos}}\right\rangle =16$?> </jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mfenced close="〉" open="〈"> <mml:mrow> <mml:msub> <mml:mrow> <mml:mi>B</mml:mi> </mml:mrow> <mml:mrow> <mml:mi>pos</mml:mi> </mml:mrow> </mml:msub> </mml:mrow> </mml:mfenced> <mml:mo>=</mml:mo> <mml:mn>16</mml:mn> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjac28a1ieqn2.gif" xlink:type="simple" /> </jats:inline-formula> mG from the dust and <jats:inline-formula> <jats:tex-math> <?CDATA $\left\langle {B}_{\mathrm{pos}}\right\rangle \sim 2$?> </jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mfenced close="〉" open="〈"> <mml:mrow> <mml:msub> <mml:mrow> <mml:mi>B</mml:mi> </mml:mrow> <mml:mrow> <mml:mi>pos</mml:mi> </mml:mrow> </mml:msub> </mml:mrow> </mml:mfenced> <mml:mo>∼</mml:mo> <mml:mn>2</mml:mn> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjac28a1ieqn3.gif" xlink:type="simple" /> </jats:inline-formula> mG from the CS emission, where each emission traces different molecular hydrogen number densities. This effectively enables a tomographic view of the magnetic field within a single ALMA observation.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>We present a multiwavelength photometric and spectroscopic analysis of 13 super-Chandrasekhar-mass/2003fg-like Type Ia supernovae (SNe Ia). Nine of these objects were observed by the Carnegie Supernova Project. The 2003fg-like SNe have slowly declining light curves (Δ<jats:italic>m</jats:italic> <jats:sub>15</jats:sub>(<jats:italic>B</jats:italic>) &lt; 1.3 mag), and peak absolute <jats:italic>B</jats:italic>-band magnitudes of −19 &lt; <jats:italic>M</jats:italic> <jats:sub> <jats:italic>B</jats:italic> </jats:sub> &lt; −21 mag. Many of the 2003fg-like SNe are located in the same part of the luminosity–width relation as normal SNe Ia. In the optical <jats:italic>B</jats:italic> and <jats:italic>V</jats:italic> bands, the 2003fg-like SNe look like normal SNe Ia, but at redder wavelengths they diverge. Unlike other luminous SNe Ia, the 2003fg-like SNe generally have only one <jats:italic>i</jats:italic>-band maximum, which peaks after the epoch of the <jats:italic>B</jats:italic>-band maximum, while their near-IR (NIR) light-curve rise times can be ≳40 days longer than those of normal SNe Ia. They are also at least 1 mag brighter in the NIR bands than normal SNe Ia, peaking above <jats:italic>M</jats:italic> <jats:sub> <jats:italic>H</jats:italic> </jats:sub> = −19 mag, and generally have negative Hubble residuals, which may be the cause of some systematics in dark-energy experiments. Spectroscopically, the 2003fg-like SNe exhibit peculiarities such as unburnt carbon well past maximum light, a large spread (8000–12,000 km s<jats:sup>−1</jats:sup>) in Si <jats:sc>ii</jats:sc> <jats:italic>λ</jats:italic>6355 velocities at maximum light with no rapid early velocity decline, and no clear <jats:italic>H</jats:italic>-band break at +10 days. We find that SNe with a larger pseudo-equivalent width of C <jats:sc>ii</jats:sc> at maximum light have lower Si <jats:sc>ii</jats:sc> <jats:italic>λ</jats:italic>6355 velocities and more slowly declining light curves. There are also multiple factors that contribute to the peak luminosity of 2003fg-like SNe. The explosion of a C–O degenerate core inside a carbon-rich envelope is consistent with these observations. Such a configuration may come from the core-degenerate scenario.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>The morphology and structure of galaxies reflect their star formation and assembly histories. We use the framework of mutual information (MI) to quantify the interdependence among several structural variables and to rank them according to their relevance for predicting the specific star formation rate (SSFR) by comparing the MI of the predictor variables with the SSFR and penalizing variables that are redundant. We apply this framework to study ∼3700 face-on star-forming galaxies (SFGs) with varying degrees of bulge dominance and central concentration and with stellar mass <jats:italic>M</jats:italic> <jats:sub>⋆</jats:sub> ≈ 10<jats:sup>9</jats:sup> <jats:italic>M</jats:italic> <jats:sub>⊙</jats:sub>−5 × 10<jats:sup>11</jats:sup> <jats:italic>M</jats:italic> <jats:sub>⊙</jats:sub> at redshift <jats:italic>z</jats:italic> = 0.02–0.12. We use the Sloan Digital Sky Survey (SDSS) Stripe 82 deep <jats:italic>i</jats:italic>-band imaging data, which improve measurements of asymmetry and bulge dominance indicators. We find that star-forming galaxies are a multiparameter family. In addition to <jats:italic>M</jats:italic> <jats:sub>⋆</jats:sub>, asymmetry emerges as the most powerful predictor of SSFR residuals of SFGs, followed by bulge prominence/concentration. Star-forming galaxies with higher asymmetry and stronger bulges have higher SSFR at a given <jats:italic>M</jats:italic> <jats:sub>⋆</jats:sub>. The asymmetry reflects both irregular spiral arms and lopsidedness in seemingly isolated SFGs and structural perturbations by galaxy interactions or mergers.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Interstellar chemistry in low-metallicity environments is crucial to understand chemical processes in the past metal-poor universe. Recent studies of interstellar molecules in nearby low-metallicity galaxies have suggested that metallicity has a significant effect on the chemistry of star-forming cores. Here we report the first detection of a hot molecular core in the extreme outer Galaxy, which is an excellent laboratory to study star formation and the interstellar medium in a Galactic low-metallicity environment. The target star-forming region, WB 89–789, is located at a galactocentric distance of 19 kpc. Our Atacama Large Millimeter/submillimeter Array observations in 241–246, 256–261, 337–341, and 349–353 GHz have detected a variety of carbon-, oxygen-, nitrogen-, sulfur-, and silicon-bearing species, including complex organic molecules (COMs) containing up to nine atoms, toward a warm (&gt;100 K) and compact (&lt;0.03 pc) region associated with a protostar (∼8 × 10<jats:sup>3</jats:sup> <jats:italic>L</jats:italic> <jats:sub>☉</jats:sub>). Deuterated species such as HDO, HDCO, D<jats:sub>2</jats:sub>CO, and CH<jats:sub>2</jats:sub>DOH are also detected. A comparison of fractional abundances of COMs relative to CH<jats:sub>3</jats:sub>OH between the outer Galactic hot core and an inner Galactic counterpart shows a remarkable similarity. On the other hand, the molecular abundances in the present source do not resemble those of low-metallicity hot cores in the Large Magellanic Cloud. The results suggest that great molecular complexity exists even in the primordial environment of the extreme outer Galaxy. The detection of another embedded protostar associated with high-velocity SiO outflows is also reported.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>We observed with Atacama Large Millimeter/submillimeter Array three deeply buried nuclei in two galaxies, NGC 4418 and Arp 220, at ∼0.″2 resolution over a total bandwidth of 67 GHz in <jats:italic>f</jats:italic> <jats:sub>rest</jats:sub> = 215–697 GHz. Here we (1) introduce our program, (2) describe our data reduction method for wide-band, high-resolution imaging spectroscopy, (3) analyze in visibilities the compact nuclei with line forests, (4) develop a continuum-based estimation method of dust opacity and gas column density in heavily obscured nuclei, which uses the buried galactic nuclei (BGN) model and is sensitive to <jats:inline-formula> <jats:tex-math> <?CDATA $\mathrm{log}({N}_{{{\rm{H}}}_{2}}/{\mathrm{cm}}^{-2})$?> </jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mi>log</mml:mi> <mml:mo stretchy="false">(</mml:mo> <mml:msub> <mml:mrow> <mml:mi>N</mml:mi> </mml:mrow> <mml:mrow> <mml:msub> <mml:mrow> <mml:mi mathvariant="normal">H</mml:mi> </mml:mrow> <mml:mrow> <mml:mn>2</mml:mn> </mml:mrow> </mml:msub> </mml:mrow> </mml:msub> <mml:mrow> <mml:mo stretchy="true">/</mml:mo> </mml:mrow> <mml:msup> <mml:mrow> <mml:mi>cm</mml:mi> </mml:mrow> <mml:mrow> <mml:mo>−</mml:mo> <mml:mn>2</mml:mn> </mml:mrow> </mml:msup> <mml:mo stretchy="false">)</mml:mo> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjac2746ieqn1.gif" xlink:type="simple" /> </jats:inline-formula> ∼ 25–26 at <jats:italic>λ</jats:italic> ∼ 1 mm, and (5) present the continuum data and diagnosis of our targets. The three continuum nuclei have major-axis FWHMs of ∼0.″1–0.″3 (20–140 pc) aligned to their rotating nuclear disks of molecular gas. However, each nucleus is described better with two or three concentric components than with a single Gaussian. The innermost cores have sizes of 0.″05–0.″10 (8–40 pc), peak brightness temperatures of ∼100–500 K at 350 GHz, and more fractional flux at lower frequencies. The intermediate components correspond to the nuclear disks. They have axial ratios of ≈0.5 and hence inclinations ≳60°. The outermost elements include the bipolar outflow from Arp 220W. We estimate 1 mm dust opacity of <jats:italic>τ</jats:italic> <jats:sub>d,1 mm</jats:sub> ≈ 2.2, 1.2, and ≲0.4, respectively, for NGC 4418, Arp 220W, and Arp 220E. The first two correspond to <jats:inline-formula> <jats:tex-math> <?CDATA $\mathrm{log}({N}_{{\rm{H}}}/{\mathrm{cm}}^{-2})\sim 26$?> </jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mi>log</mml:mi> <mml:mo stretchy="false">(</mml:mo> <mml:msub> <mml:mrow> <mml:mi>N</mml:mi> </mml:mrow> <mml:mrow> <mml:mi mathvariant="normal">H</mml:mi> </mml:mrow> </mml:msub> <mml:mrow> <mml:mo stretchy="true">/</mml:mo> </mml:mrow> <mml:msup> <mml:mrow> <mml:mi>cm</mml:mi> </mml:mrow> <mml:mrow> <mml:mo>−</mml:mo> <mml:mn>2</mml:mn> </mml:mrow> </mml:msup> <mml:mo stretchy="false">)</mml:mo> <mml:mo>∼</mml:mo> <mml:mn>26</mml:mn> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjac2746ieqn2.gif" xlink:type="simple" /> </jats:inline-formula> for conventional dust-opacity laws, and hence the nuclei are highly Compton thick.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>We report an observational study of the Galactic H <jats:sc>ii</jats:sc> region Sh 2-305/S305 using the [C <jats:sc>ii</jats:sc>] 158 <jats:italic>μ</jats:italic>m line data, which are used to examine the gas dynamics and structure of photodissociation regions. The integrated [C <jats:sc>ii</jats:sc>] emission map at [39.4, 49.5] km s<jats:sup>−1</jats:sup> spatially traces two shell-like structures (i.e., inner and outer neutral shells) having a total mass of ∼565 <jats:italic>M</jats:italic> <jats:sub>⊙</jats:sub>. The inner neutral shell encompasses an O9.5V star at its center and has a compact ring-like appearance. However, the outer shell is seen with more extended and diffuse [C <jats:sc>ii</jats:sc>] emission, hosting an O8.5V star at its center, and surrounds the inner neutral shell. The velocity channel maps and position–velocity diagrams confirm the presence of a compact [C <jats:sc>ii</jats:sc>] shell embedded in the diffuse outer shell, and both the shells seem to expand with <jats:inline-formula> <jats:tex-math> <?CDATA ${v}_{\exp }\sim 1.3$?> </jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msub> <mml:mrow> <mml:mi>v</mml:mi> </mml:mrow> <mml:mrow> <mml:mi>exp</mml:mi> </mml:mrow> </mml:msub> <mml:mo>∼</mml:mo> <mml:mn>1.3</mml:mn> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjac2a44ieqn1.gif" xlink:type="simple" /> </jats:inline-formula> km s<jats:sup>−1</jats:sup>. The outer shell appears to be older than the inner shell, hinting that these shells are formed sequentially. The [C <jats:sc>ii</jats:sc>] profiles are examined toward S305, which are either double peaked or blue skewed and have the brighter redshifted component. The redshifted and blueshifted components spatially trace the inner and outer neutral shell geometry, respectively. The ionized, neutral, and molecular zones in S305 are seen adjacent to one another around the O-type stars. The regularly spaced dense molecular and dust clumps (mass ∼10–10<jats:sup>3</jats:sup> <jats:italic>M</jats:italic> <jats:sub>⊙</jats:sub>) are investigated around the neutral shells, which might have originated as a result of gravitational instability in the shell of collected materials.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>We compare results of simulations of solar facular-like conditions performed using the numerical codes <jats:monospace>MURaM</jats:monospace> and <jats:monospace>STAGGER</jats:monospace>. Both simulation sets have a similar setup, including the initial condition of ≈200 G vertical magnetic flux. After interpolating the output physical quantities to constant optical depth, we compare them and test them against inversion results from solar observations. From the snapshots, we compute the monochromatic continuum in the visible and infrared, and the full Stokes vector of the Fe <jats:sc>i</jats:sc> spectral line pair around 6301–6302 Å. We compare the predicted spectral lines (at the simulation resolution and after smearing to the HINODE SP/SOT resolution) in terms of their main parameters for the Stokes I line profiles, and of their area and amplitude asymmetry for the Stokes V profiles. The codes produce magnetoconvection with similar appearance and distribution in temperature and velocity. The results also closely match the values from recent relevant solar observations. Although the overall distribution of the magnetic field is similar in both radiation-magnetohydrodynamic (RMHD) simulation sets, a detailed analysis reveals substantial disagreement in the field orientation, which we attribute to the differing boundary conditions. The resulting differences in the synthetic spectra disappear after spatial smearing to the resolution of the observations. We conclude that the two sets of simulations provide robust models of solar faculae. Nevertheless, we also find differences that call for caution when using results from RMHD simulations to interpret solar observational data.</jats:p>