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<jats:title>Abstract</jats:title> <jats:p>The Davis–Chandrasekhar–Fermi (DCF) method provides an indirect way to estimate the magnetic field strength from statistics of magnetic field orientations. We compile all the previous DCF estimations from polarized dust emission observations and recalculate the magnetic field strength of the selected samples with the new DCF correction factors in Liu et al. We find the magnetic field scales with the volume density as <jats:italic>B</jats:italic> ∝ <jats:italic>n</jats:italic> <jats:sup>0.57</jats:sup>. However, the estimated power-law index of the observed <jats:italic>B</jats:italic>–<jats:italic>n</jats:italic> relation has large uncertainties and may not be comparable to the <jats:italic>B</jats:italic>–<jats:italic>n</jats:italic> relation of theoretical models. A clear trend of decreasing magnetic viral parameter (i.e., increasing mass-to-flux ratio in units of critical value) with increasing column density is found in the sample, which suggests the magnetic field dominates the gravity at lower densities but cannot compete with the gravity at higher densities. This finding also indicates that the magnetic flux is dissipated at higher column densities due to ambipolar diffusion or magnetic reconnection, and the accumulation of mass at higher densities may be by mass flows along the magnetic field lines. Both sub-Alfvénic and super-Alfvénic states are found in the sample, with the average state being approximately trans-Alfvénic.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>V606 Centauri (V606 Cen) is an early B-type close binary with an orbital period of 1.4950935 days, and its complete light curves are very difficult to observe on the ground. By analyzing the continuous light curve obtained by TESS, we found that it is a marginal contact binary with a very low fill-out factor of about 2%. The <jats:italic>O</jats:italic> − <jats:italic>C</jats:italic> diagram of V606 Cen is constructed for the first time based on 118.8 yr of eclipse times. The <jats:italic>O</jats:italic> − <jats:italic>C</jats:italic> diagram has been found to show a downward parabolic change together with a cyclic oscillation with a semiamplitude of 0.0545 days and a period of 88.3 yr. The downward parabolic variation reveals a linear period decrease at a rate of <jats:italic>dP</jats:italic>/<jats:italic>dt</jats:italic> = −2.08 × 10<jats:sup>−7</jats:sup> days yr<jats:sup>−1</jats:sup> that can be explained by the mass transfer from the more massive component to the less massive one. Both the marginal contact configuration and the continuous period decrease suggest that V606 Cen is a newly formed contact binary via Case A mass transfer. The cyclic change in the <jats:italic>O</jats:italic> − <jats:italic>C</jats:italic> diagram can be explained by the light-travel time effect via the presence of a third body. The lowest mass of the tertiary companion is determined to be <jats:italic>M</jats:italic> <jats:sub>3</jats:sub> = 4.51 (±0.43) <jats:italic>M</jats:italic> <jats:sub>⊙</jats:sub> and the tertiary is orbiting around the central eclipsing binary in a nearly circular orbit (<jats:italic>e</jats:italic> = 0.33). All of the results indicate that V606 Cen is a newly formed massive contact binary in a hierarchical triple system.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>We provide a method for estimating the projected density distribution <jats:inline-formula> <jats:tex-math> <?CDATA ${\bar{n}}_{2}{w}_{p}({r}_{p})$?> </jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msub> <mml:mrow> <mml:mover accent="true"> <mml:mrow> <mml:mi>n</mml:mi> </mml:mrow> <mml:mrow> <mml:mo>¯</mml:mo> </mml:mrow> </mml:mover> </mml:mrow> <mml:mrow> <mml:mn>2</mml:mn> </mml:mrow> </mml:msub> <mml:msub> <mml:mrow> <mml:mi>w</mml:mi> </mml:mrow> <mml:mrow> <mml:mi>p</mml:mi> </mml:mrow> </mml:msub> <mml:mo stretchy="false">(</mml:mo> <mml:msub> <mml:mrow> <mml:mi>r</mml:mi> </mml:mrow> <mml:mrow> <mml:mi>p</mml:mi> </mml:mrow> </mml:msub> <mml:mo stretchy="false">)</mml:mo> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjac38a2ieqn1.gif" xlink:type="simple" /> </jats:inline-formula> of photometric objects around spectroscopic objects in a spectroscopic survey. This quantity describes the distribution of photometric sources with certain physical properties (e.g., luminosity, mass, and color) around cosmic webs (PAC) traced by the spectroscopic objects. The method can make full use of current and future deep and wide photometric surveys to explore the formation of galaxies up to medium redshift (<jats:italic>z</jats:italic> <jats:sub> <jats:italic>s</jats:italic> </jats:sub> &lt; 2)<jats:xref ref-type="fn" rid="apjac38a2fn1"> <jats:sup>3</jats:sup> </jats:xref> <jats:fn id="apjac38a2fn1"> <jats:label> <jats:sup>3</jats:sup> </jats:label> <jats:p>Throughout the paper, we use <jats:italic>z</jats:italic> <jats:sub> <jats:italic>s</jats:italic> </jats:sub> for redshift, <jats:italic>z</jats:italic> for the <jats:italic>z</jats:italic>-band magnitude, <jats:italic>z</jats:italic> <jats:sub> <jats:italic>p</jats:italic> </jats:sub> for the photometric redshift.</jats:p> </jats:fn> with the aid of cosmological spectroscopic surveys that sample only a fairly limited species of objects (e.g., emission line galaxies). As an example, we apply the PAC method to the CMASS spectroscopic and HSC-SSP PDR2 photometric samples to explore the distribution of galaxies for a wide range of stellar masses from 10<jats:sup>9.0</jats:sup> to 10<jats:sup>12.0</jats:sup> <jats:italic>M</jats:italic> <jats:sub>⊙</jats:sub> around massive galaxies at <jats:italic>z</jats:italic> <jats:sub> <jats:italic>s</jats:italic> </jats:sub> ≈ 0.6. Using the abundance-matching method, we model <jats:inline-formula> <jats:tex-math> <?CDATA ${\bar{n}}_{2}{w}_{p}({r}_{p})$?> </jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msub> <mml:mrow> <mml:mover accent="true"> <mml:mrow> <mml:mi>n</mml:mi> </mml:mrow> <mml:mrow> <mml:mo>¯</mml:mo> </mml:mrow> </mml:mover> </mml:mrow> <mml:mrow> <mml:mn>2</mml:mn> </mml:mrow> </mml:msub> <mml:msub> <mml:mrow> <mml:mi>w</mml:mi> </mml:mrow> <mml:mrow> <mml:mi>p</mml:mi> </mml:mrow> </mml:msub> <mml:mo stretchy="false">(</mml:mo> <mml:msub> <mml:mrow> <mml:mi>r</mml:mi> </mml:mrow> <mml:mrow> <mml:mi>p</mml:mi> </mml:mrow> </mml:msub> <mml:mo stretchy="false">)</mml:mo> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjac38a2ieqn2.gif" xlink:type="simple" /> </jats:inline-formula> in <jats:italic>N</jats:italic>-body simulation using Markov chain Monte Carlo sampling, and we accurately measure the stellar–halo mass relation and stellar mass function for the whole mass range. We can also measure the conditional stellar mass function of satellites for central galaxies of different mass. The PAC method has many potential applications for studying the evolution of galaxies.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>We present a method that utilizes autocorrelation functions from long-term precision broadband differential light curves to estimate the average lifetimes of starspot groups for two large samples of Kepler stars: stars with and without previously known rotation periods. Our method is calibrated by comparing the strengths of the first few normalized autocorrelation peaks using ensembles of models that have various starspot lifetimes. We find that we must mix models of short and long lifetimes together (in heuristically determined ratios) to align the models with the Kepler data. Our fundamental result is that short starspot-group lifetimes (one to four rotations) are implied when the first normalized peak is weaker than about 0.4, long lifetimes (15 or greater) are implied when it is greater than about 0.7, and in between are the intermediate cases. Rotational lifetimes can be converted to physical lifetimes if the rotation period is known. Stars with shorter rotation periods tend to have longer rotational (but not physical) spot lifetimes, and cooler stars tend to have longer physical spot lifetimes than warmer stars with the same rotation period. The distributions of the physical lifetimes are log-normal for both samples and generally longer in the first sample. The shorter lifetimes in the stars without known periods probably explain why their periods are difficult to measure. Some stars exhibit longer than average physical starspot lifetimes; their percentage drops with increasing temperature from nearly half at 3000 K to nearly zero for hotter than 6000 K.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Understanding how material accretes onto the rotationally supported disk from the surrounding envelope of gas and dust in the youngest protostellar systems is important for describing how disks are formed. Magnetohydrodynamic simulations of magnetized, turbulent disk formation usually show spiral-like streams of material (accretion flows) connecting the envelope to the disk. However, accretion flows in these early stages of protostellar formation still remain poorly characterized, due to their low intensity, and possibly some extended structures are disregarded as being part of the outflow cavity. We use ALMA archival data of a young Class 0 protostar, Lupus 3-MMS, to uncover four extended accretion flow–like structures in C<jats:sup>18</jats:sup>O that follow the edges of the outflows. We make various types of position–velocity cuts to compare with the outflows and find the extended structures are not consistent with the outflow emission, but rather more consistent with a simple infall model. We then use a dendrogram algorithm to isolate five substructures in position–position–velocity space. Four out of the five substructures fit well (&gt;95%) with our simple infall model, with specific angular momenta between 2.7–6.9 × 10<jats:sup>−4</jats:sup> km s<jats:sup>−1</jats:sup> pc and mass-infall rates of 0.5–1.1 × 10<jats:sup>−6</jats:sup> <jats:italic>M</jats:italic> <jats:sub>⊙</jats:sub> yr<jats:sup>−1</jats:sup>. Better characterization of the physical structure in the supposed “outflow cavities” is important to disentangle the true outflow cavities and accretion flows.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>We use the Keck Cosmic Web Imager integral field unit spectrograph to (1) measure the global stellar population parameters for the ultra-diffuse galaxy (UDG) Dragonfly 44 (DF44) to much higher precision than previously possible for any UDG and (2) for the first time measure spatially resolved stellar population parameters of a UDG. We find that DF44 falls below the mass–metallicity relation established by canonical dwarf galaxies both in and beyond the Local Group. We measure a flat radial age gradient (<jats:inline-formula> <jats:tex-math> <?CDATA ${m}_{\mathrm{logage}}=+{0.01}_{-0.08}^{+0.08}$?> </jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msub> <mml:mrow> <mml:mi>m</mml:mi> </mml:mrow> <mml:mrow> <mml:mi>logage</mml:mi> </mml:mrow> </mml:msub> <mml:mo>=</mml:mo> <mml:mo>+</mml:mo> <mml:msubsup> <mml:mrow> <mml:mn>0.01</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>−</mml:mo> <mml:mn>0.08</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>+</mml:mo> <mml:mn>0.08</mml:mn> </mml:mrow> </mml:msubsup> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjac341eieqn1.gif" xlink:type="simple" /> </jats:inline-formula> log Gyr kpc<jats:sup>−1</jats:sup>) and a flat to positive metallicity gradient (<jats:inline-formula> <jats:tex-math> <?CDATA ${m}_{[\mathrm{Fe}/{\rm{H}}]}=+{0.09}_{-0.12}^{+0.11}$?> </jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msub> <mml:mrow> <mml:mi>m</mml:mi> </mml:mrow> <mml:mrow> <mml:mo stretchy="false">[</mml:mo> <mml:mi>Fe</mml:mi> <mml:mrow> <mml:mo stretchy="true">/</mml:mo> </mml:mrow> <mml:mi mathvariant="normal">H</mml:mi> <mml:mo stretchy="false">]</mml:mo> </mml:mrow> </mml:msub> <mml:mo>=</mml:mo> <mml:mo>+</mml:mo> <mml:msubsup> <mml:mrow> <mml:mn>0.09</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>−</mml:mo> <mml:mn>0.12</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>+</mml:mo> <mml:mn>0.11</mml:mn> </mml:mrow> </mml:msubsup> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjac341eieqn2.gif" xlink:type="simple" /> </jats:inline-formula> dex kpc<jats:sup>−1</jats:sup>), which are inconsistent with the gradients measured in similarly pressure-supported dwarf galaxies. We also measure a negative [Mg/Fe] gradient (<jats:inline-formula> <jats:tex-math> <?CDATA ${m}_{[\mathrm{Mg}/\mathrm{Fe}]}=-{0.20}_{-0.18}^{+0.18}$?> </jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msub> <mml:mrow> <mml:mi>m</mml:mi> </mml:mrow> <mml:mrow> <mml:mo stretchy="false">[</mml:mo> <mml:mi>Mg</mml:mi> <mml:mrow> <mml:mo stretchy="true">/</mml:mo> </mml:mrow> <mml:mi>Fe</mml:mi> <mml:mo stretchy="false">]</mml:mo> </mml:mrow> </mml:msub> <mml:mo>=</mml:mo> <mml:mo>−</mml:mo> <mml:msubsup> <mml:mrow> <mml:mn>0.20</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>−</mml:mo> <mml:mn>0.18</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>+</mml:mo> <mml:mn>0.18</mml:mn> </mml:mrow> </mml:msubsup> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjac341eieqn3.gif" xlink:type="simple" /> </jats:inline-formula> ) dex kpc<jats:sup>−1</jats:sup> such that the central 1.5 kpc of DF44 has stellar population parameters comparable to metal-poor globular clusters. Overall, DF44 does not have internal properties similar to other dwarf galaxies and is inconsistent with it having been puffed up through a prolonged, bursty star formation history, as suggested by some simulations. Rather, the evidence indicates that DF44 experienced an intense epoch of “inside-out” star formation and then quenched early and catastrophically, such that star formation was cut off more quickly than in canonical dwarf galaxies.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>The observed atmospheric spectrum of exoplanets and brown dwarfs depends critically on the presence and distribution of atmospheric condensates. The Ackerman and Marley methodology for predicting the vertical distribution of condensate particles is widely used to study cloudy atmospheres and has recently been implemented in an open-source python package, Virga. The model relies upon input parameter <jats:italic>f</jats:italic> <jats:sub>sed</jats:sub>, the sedimentation efficiency, which until now has been held constant. The relative simplicity of this model renders it useful for retrieval studies due to its rapidly attainable solutions. However, comparisons with more complex microphysical models such as CARMA have highlighted inconsistencies between the two approaches, namely that the cloud parameters needed for radiative transfer produced by Virga are dissimilar to those produced by CARMA. To address these discrepancies, we have extended the original Ackerman and Marley methodology in Virga to allow for non-constant <jats:italic>f</jats:italic> <jats:sub>sed</jats:sub> values, in particular, those that vary with altitude. We discuss one such parameterization and compare the cloud mass mixing ratio produced by Virga with constant and variable <jats:italic>f</jats:italic> <jats:sub>sed</jats:sub> profiles to that produced by CARMA. We find that the variable <jats:italic>f</jats:italic> <jats:sub>sed</jats:sub> formulation better captures the profile produced by CARMA with heterogeneous nucleation, yet performs comparatively to constant <jats:italic>f</jats:italic> <jats:sub>sed</jats:sub> for homogeneous nucleation. In general, Virga has the capacity to handle any <jats:italic>f</jats:italic> <jats:sub>sed</jats:sub> with an explicit anti-derivative, permitting a plethora of alternative cloud profiles that are otherwise unattainable by constant <jats:italic>f</jats:italic> <jats:sub>sed</jats:sub> values. The ensuing flexibility has the potential to better agree with increasingly complex models and observed data.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>The parametric decay of finite-size Alfvén waves in nonperiodic low-beta plasmas is investigated using one-dimensional (1D) hybrid simulations. Compared with the usual small periodic system, a wave packet in a large system under the absorption boundary condition shows different decay dynamics, including reduced energy transfer, localized density cavitation, and ion heating. The resulting Alfvén wave dynamics are influenced by several factors relating to this instability, including the growth rate, central wave frequency, and unstable bandwidth. A final steady state of the wave packet may be achieved when the instability does not have enough time to develop within the residual packet, and the packet size shows well-defined scaling dependencies on the growth rate, wave amplitude, and plasma beta. Under the proper conditions, enhanced secondary decay can also be excited in the form of a narrow, amplified wave packet. These results may help to interpret laboratory and spacecraft observations of Alfvén waves, and to refine our understanding of the associated energy transport and ion heating.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>We present the <jats:italic>H</jats:italic> <jats:sub>160</jats:sub> morphological catalogs for the COSMOS-DASH survey, the largest area near-IR survey using HST-WFC3 to date. Utilizing the “Drift And SHift” observing technique for HST-WFC3 imaging, the COSMOS-DASH survey imaged approximately 0.5 deg<jats:sup>2</jats:sup> of the UltraVISTA deep stripes (0.7 deg<jats:sup>2</jats:sup>, when combined with archival data). Global structural parameters are measured for 51,586 galaxies within COSMOS-DASH using GALFIT (excluding the CANDELS area) with detection using a deep multi-band HST image. We recover consistent results with those from the deeper 3D-HST morphological catalogs, finding that, in general, sizes and Sérsic indices of typical galaxies are accurate to limiting magnitudes of <jats:italic>H</jats:italic> <jats:sub>160</jats:sub> &lt; 23 and <jats:italic>H</jats:italic> <jats:sub>160</jats:sub> &lt; 22 ABmag, respectively. In size-mass parameter space, galaxies in COSMOS-DASH demonstrate robust morphological measurements out to <jats:italic>z</jats:italic> ∼ 2 and down to <jats:inline-formula> <jats:tex-math> <?CDATA $\mathrm{log}({M}_{\star }/{M}_{\odot })\sim 9$?> </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>M</mml:mi> </mml:mrow> <mml:mrow> <mml:mo>⋆</mml:mo> </mml:mrow> </mml:msub> <mml:mrow> <mml:mo stretchy="true">/</mml:mo> </mml:mrow> <mml:msub> <mml:mrow> <mml:mi>M</mml:mi> </mml:mrow> <mml:mrow> <mml:mo>⊙</mml:mo> </mml:mrow> </mml:msub> <mml:mo stretchy="false">)</mml:mo> <mml:mo>∼</mml:mo> <mml:mn>9</mml:mn> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjac341cieqn1.gif" xlink:type="simple" /> </jats:inline-formula>. With the advantage of the larger area of COSMOS-DASH, we measure a flattening of the quiescent size-mass relation below <jats:inline-formula> <jats:tex-math> <?CDATA $\mathrm{log}({M}_{\star }/{M}_{\odot })\sim 10.5$?> </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>M</mml:mi> </mml:mrow> <mml:mrow> <mml:mo>⋆</mml:mo> </mml:mrow> </mml:msub> <mml:mrow> <mml:mo stretchy="true">/</mml:mo> </mml:mrow> <mml:msub> <mml:mrow> <mml:mi>M</mml:mi> </mml:mrow> <mml:mrow> <mml:mo>⊙</mml:mo> </mml:mrow> </mml:msub> <mml:mo stretchy="false">)</mml:mo> <mml:mo>∼</mml:mo> <mml:mn>10.5</mml:mn> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjac341cieqn2.gif" xlink:type="simple" /> </jats:inline-formula> that persists out to <jats:italic>z</jats:italic> ∼ 2. We show that environment is not the primary driver of this flattening, at least out to <jats:italic>z</jats:italic> = 1.2, whereas internal physical processes may instead govern the structural evolution.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Upon entering the tidal sphere of a supermassive black hole, a star is ripped apart by tides and transformed into a stream of debris. The ultimate fate of that debris, and the properties of the bright flare that is produced and observed, depends on a number of parameters, including the energy of the center of mass of the original star. Here we present the results of a set of smoothed particle hydrodynamics simulations in which a 1<jats:italic>M</jats:italic> <jats:sub>⊙</jats:sub>, <jats:italic>γ</jats:italic> = 5/3 polytrope is disrupted by a 10<jats:sup>6</jats:sup> <jats:italic>M</jats:italic> <jats:sub>⊙</jats:sub> supermassive black hole. Each simulation has a pericenter distance of <jats:italic>r</jats:italic> <jats:sub>p</jats:sub> = <jats:italic>r</jats:italic> <jats:sub>t</jats:sub> (i.e., <jats:italic>β</jats:italic> ≡ <jats:italic>r</jats:italic> <jats:sub>t</jats:sub>/<jats:italic>r</jats:italic> <jats:sub>p</jats:sub> = 1 with <jats:italic>r</jats:italic> <jats:sub>t</jats:sub> the tidal radius), and we vary the eccentricity <jats:italic>e</jats:italic> of the stellar orbit from <jats:italic>e</jats:italic> = 0.8 up to <jats:italic>e</jats:italic> = 1.20 and study the nature of the fallback of debris onto the black hole and the long-term fate of the unbound material. For simulations with eccentricities <jats:italic>e</jats:italic> ≲ 0.98, the fallback curve has a distinct, three-peak structure that is induced by self-gravity. For simulations with eccentricities <jats:italic>e</jats:italic> ≳ 1.06, the core of the disrupted star reforms following its initial disruption. Our results have implications for, e.g., tidal disruption events produced by supermassive black hole binaries.</jats:p>