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<jats:title>Abstract</jats:title> <jats:p>Radio relics are elongated sources related to shocks driven by galaxy cluster merger events. Although these objects are highly polarized at GHz frequencies (≳20%), high-resolution studies of their polarization properties are still lacking. We present the first high-resolution and high-sensitivity polarimetry study of the merging galaxy cluster CIZA J2242.8+5301 in the 1–4 GHz frequency band. We use the <jats:italic>QU</jats:italic>-fitting approach to model the Stokes <jats:italic>I</jats:italic>, <jats:italic>Q</jats:italic>, and <jats:italic>U</jats:italic> emission, obtaining best-fit intrinsic polarization fraction (<jats:italic>p</jats:italic> <jats:sub>0</jats:sub>), intrinsic polarization angle (<jats:italic>χ</jats:italic> <jats:sub>0</jats:sub>), rotation measure (RM), and wavelength-dependent depolarization (<jats:italic>σ</jats:italic> <jats:sub>RM</jats:sub>) maps of the cluster. Our analysis focuses on the northern relic (RN). For the first time in a radio relic, we observe a decreasing polarization fraction in the downstream region. Our findings are possibly explained by geometrical projections and/or by decreasing of the magnetic field anisotropy toward the cluster center. From the amount of depolarization of the only detected background radio galaxy, we estimate a turbulent magnetic field strength of <jats:italic>B</jats:italic> <jats:sub>turb</jats:sub> ∼ 5.6 <jats:italic>μ</jats:italic>G in the relic. Finally, we observe RM fluctuations of about 30 rad m<jats:sup>−2</jats:sup> around the median value of 140.8 rad m<jats:sup>−2</jats:sup> at the relic position.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Solar flare termination shocks have been suggested as one of the viable mechanisms for accelerating electrons and ions to high energies. Observational evidence of such shocks, however, remains rare. Using radio dynamic spectroscopic imaging of a long-duration C1.9 flare obtained by the Karl G. Jansky Very Large Array (VLA), Chen et al. suggested that a type of coherent radio bursts, referred to as “stochastic spike bursts,” were radio signatures of nonthermal electrons interacting with myriad density fluctuations at the front of a flare termination shock. Here we report another stochastic spike burst event recorded during the extended energy release phase of a long-duration M8.4-class eruptive flare on 2012 March 10. VLA radio spectroscopic imaging of the spikes in 1.0–1.6 GHz shows that, similar to the case of Chen et al., the burst centroids form an extended, ∼10″-long structure in the corona. By combining extreme-ultraviolet imaging observations of the flare from two vantage points with hard X-ray and ultraviolet observations of the flare ribbon brightenings, we reconstruct the flare arcade in three dimensions. The results show that the spike source is located at ∼60 Mm above the flare arcade, where a diffuse supra-arcade fan and multitudes of plasma downflows are present. Although the flare arcade and ribbons seen during the impulsive phase do not allow us to clearly understand how the observed spike source location is connected to the flare geometry, the cooling flare arcade observed 2 hr later suggests that the spikes are located in the above-the-loop-top region, where a termination shock presumably forms.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>We report an analysis of the dust disk around DM Tau, newly observed with the Atacama Large Millimeter/submillimeter Array (ALMA) at 1.3 mm. The ALMA observations with high sensitivity (8.4 <jats:italic>μ</jats:italic>Jy beam<jats:sup>–1</jats:sup>) and high angular resolution (35 mas, 5.1 au) detect two asymmetries on the ring at <jats:italic>r</jats:italic> ∼ 20 au. They could be two vortices in early evolution, the destruction of a large-scale vortex, or double continuum emission peaks with different dust sizes. We also found millimeter emissions with ∼50 <jats:italic>μ</jats:italic>Jy (a lower-limit dust mass of 0.3 <jats:italic>M</jats:italic> <jats:sub>Moon</jats:sub>) inside the 3 au ring. To characterize these emissions, we modeled the spectral energy distribution (SED) of DM Tau using a Monte Carlo radiative transfer code. We found that an additional ring at <jats:italic>r</jats:italic> = 1 au could explain both the DM Tau SED and the central point source. The disk midplane temperature at the 1 au ring calculated in our modeling is less than the typical water sublimation temperature of 150 K, prompting the possibility of forming small icy planets there.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>A failed core-collapse supernova from a nonrotating progenitor can eject mass due to a weakening of gravity associated with neutrino emission from the protoneutron star. This mechanism yields observable transients and sets an upper limit on the mass of the black hole (BH) remnant. Previous global simulations of this mechanism have included neutrino losses parametrically, however, with direct implications for the ejecta mass and energy. Here we evolve the inner supernova core with a spherically symmetric, general-relativistic neutrino radiation-hydrodynamic code until BH formation. We then use the result in a Newtonian code that follows the response of the outer layers of the star to the change in gravity and resolves the surface pressure scale height. We find that the dense-matter equation of state (EOS) can introduce a factor of ∼2 variation in gravitational mass lost to neutrinos, with a stiff EOS matching previous parametric results and a soft EOS yielding lower ejecta masses and energies by a factor of several. This difference is caused primarily by the longer time to BH formation in stiffer EOSs. With a soft EOS, our red and yellow supergiant progenitors fail to unbind mass if hydrogen recombination energy is not included. Using a linear ramp in time for mass-energy lost to neutrinos (with suitable parameters) yields a stellar response within ∼10% of that obtained using the detailed history of neutrino losses. Our results imply quantitative but not qualitative modifications to previous predictions for shock breakout, plateau emission, and final BH masses from these events.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>We present a search for new planetary-mass members of nearby young moving groups (YMGs) using astrometry for 694 T and Y dwarfs, including 447 objects with parallaxes, mostly produced by recent large parallax programs from UKIRT and Spitzer. Using the BANYAN Σ and LACEwING algorithms, we identify 30 new candidate YMG members, with spectral types of T0–T9 and distances of 10–43 pc. Some candidates have unusually red colors and/or faint absolute magnitudes compared to field dwarfs with similar spectral types, providing supporting evidence for their youth, including four early-T dwarfs. We establish one of these, the variable T1.5 dwarf 2MASS J21392676+0220226, as a new planetary-mass member (<jats:inline-formula> <jats:tex-math> <?CDATA ${14.6}_{-1.6}^{+3.2}$?> </jats:tex-math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjabe3faieqn1.gif" xlink:type="simple" /> </jats:inline-formula> <jats:italic>M</jats:italic> <jats:sub>Jup</jats:sub>) of the Carina-Near group (200 ± 50 Myr) based on its full six-dimensional kinematics, including a new parallax measurement from CFHT. The high-amplitude variability of this object is suggestive of a young age, given the coexistence of variability and youth seen in previously known YMG T dwarfs. Our four latest-type (T8–T9) YMG candidates, WISE J031624.35+430709.1, ULAS J130217.21+130851.2, WISEPC J225540.74–311841.8, and WISE J233226.49–432510.6, if confirmed, will be the first free-floating planets (≈2–6 <jats:italic>M</jats:italic> <jats:sub>Jup</jats:sub>) whose ages and luminosities are compatible with both hot-start and cold-start evolutionary models, and thus overlap with the properties of the directly imaged planet 51 Eri b. Several of our early/mid-T candidates have peculiar near-infrared spectra, indicative of heterogenous photospheres or unresolved binarity. Radial velocity measurements needed for final membership assessment for most of our candidates await upcoming 20–30 m class telescopes. In addition, we compile all 15 known T7–Y1 benchmarks and derive a homogeneous set of their effective temperatures, surface gravities, radii, and masses.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>We derive the mass–radius relation and mass function of molecular clumps in the Large Magellanic Cloud (LMC) and interpret them in terms of the simple feedback model proposed by Fall et al. (FKM). Our work utilizes the dendrogram-based catalog of clumps compiled by Wong et al. from <jats:sup>12</jats:sup>CO and <jats:sup>13</jats:sup>CO maps of six giant molecular clouds in the LMC observed with the Atacama Large Millimeter Array. The Magellanic Clouds are the only external galaxies for which this type of analysis is possible at the necessary spatial resolution (∼1 pc). We find that the mass–radius relation and mass function of LMC clumps have power-law forms, <jats:italic>R</jats:italic> ∝ <jats:italic>M</jats:italic> <jats:sup> <jats:italic>α</jats:italic> </jats:sup> and <jats:inline-formula> <jats:tex-math> <?CDATA ${dN}/{dM}\propto {M}^{\beta }$?> </jats:tex-math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjabe12cieqn1.gif" xlink:type="simple" /> </jats:inline-formula>, with indices <jats:italic>α</jats:italic> = 0.36 ± 0.03 and <jats:italic>β</jats:italic> = −1.8 ± 0.1 over the mass ranges 10<jats:sup>2</jats:sup> <jats:italic>M</jats:italic> <jats:sub>⊙</jats:sub> ≲ <jats:italic>M</jats:italic> ≲ 10<jats:sup>5</jats:sup> <jats:italic>M</jats:italic> <jats:sub>⊙</jats:sub> and 10<jats:sup>2</jats:sup> <jats:italic>M</jats:italic> <jats:sub>⊙</jats:sub> ≲<jats:italic>M</jats:italic> ≲ 10<jats:sup>4</jats:sup> <jats:italic>M</jats:italic> <jats:sub>⊙</jats:sub>, respectively. With these values of <jats:italic>α</jats:italic> and <jats:italic>β</jats:italic> for the clumps (i.e., protoclusters), the predicted index for the mass function of young LMC clusters from the FKM model is <jats:italic>β</jats:italic> ≈ 1.7, in good agreement with the observed index. The situation portrayed here for clumps and clusters in the LMC replicates that in the Milky Way.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>We perform streaming-instability simulations at Hill density and beyond to demonstrate that planetesimal formation is not completed when pebble accumulations exceed the local Hill density. We find that Hill density is not a sufficient criterion for further gravitational collapse of a pebble cloud into a planetesimal, but that additionally the accumulated mass has to be large enough to overcome turbulent diffusion. A Toomre analysis of the system indicates that linear self-gravity modes play no role on the scale of our numerical simulation. We nevertheless find that self-gravity, by vertically contracting the pebble layer, increases the strength of turbulence, which is either an indication of Kelvin–Helmholtz instability or a boost of the streaming instability. We furthermore determine the Bonnor–Ebert central density to which a pebble cloud of a given mass has to be compressed before it would be able to continue contraction against internal diffusion. As the equivalent “solid body” size of the pebble cloud scales with the central density to the power of −1/6, it is much easier to have a pebble cloud of 100 km equivalent size to collapse than one of 10 km for the same level of turbulent diffusion. This can explain the lack of small bodies in the solar system and predicts small objects will form at large pebble-to-gas ratios, so either in the outskirts of the solar nebula or at late times of generally reduced gas mass.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>In image processing, source detections are inevitably affected by the presence of the geometric boundaries in the images, including the physical boundaries of the CCD, and the boundaries of masked regions due to column defects, bright diffraction spikes, etc. These boundary conditions make the source detection process not statistically isotropic and can lead to additive shear bias near the boundaries. We build a phenomenological model to understand the bias, and propose a simple method to effectively eliminate the influence of geometric boundaries on shear measurement. We demonstrate the accuracy and efficiency of this method using both simulations and the <jats:italic>z</jats:italic>-band imaging data from the third data release of the DECam Legacy Survey.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>We generalize the stochastic theory of hierarchical clustering presented in Paper I by Lapi &amp; Danese to derive the (conditional) halo progenitor mass function and the related large-scale bias. Specifically, we present a stochastic differential equation that describes fluctuations in the mass growth of progenitor halos of given descendant mass and redshift, as driven by a multiplicative Gaussian white noise involving the power spectrum and the spherical collapse threshold of density perturbations. We demonstrate that, as cosmic time passes, the noise yields an average drift of the progenitors toward larger masses, which quantitatively renders the expectation from the standard extended Press and Schechter (EPS) theory. We solve the Fokker–Planck equation associated with the stochastic dynamics, and obtain as an exact, stationary solution, the EPS progenitor mass function. Then we introduce a modification of the stochastic equation in terms of a mass-dependent collapse threshold modulating the noise, and solve analytically the associated Fokker–Planck equation for the progenitor mass function. The latter is found to be in excellent agreement with the outcomes of <jats:italic>N</jats:italic>-body simulations; even more remarkably, this is achieved with the same shape of the collapse threshold used in Paper I to reproduce the halo mass function. Finally, we exploit the above results to compute the large-scale halo bias, and find it in pleasing agreement with the <jats:italic>N</jats:italic>-body outcomes. All in all, the present paper illustrates that the stochastic theory of hierarchical clustering introduced in Paper I can describe effectively not only halos’ abundance, but also their progenitor distribution and their correlation with the large-scale environment across cosmic times.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>The current tension between the direct and the early-universe measurements of the Hubble constant, <jats:italic>H</jats:italic> <jats:sub>0</jats:sub>, requires detailed scrutiny of all the data and methods used in the studies on both sides of the debate. The Cepheids in the Type Ia supernova (SN Ia) host galaxy NGC 5584 played a key role in the local measurement of <jats:italic>H</jats:italic> <jats:sub>0</jats:sub>. The SH0ES project used the observations of this galaxy to derive a relation between the Cepheids’ periods and ratios of their amplitudes in different optical bands of the Hubble Space Telescope and used these relations to analyze the light curves of the Cepheids in around half of the current sample of local SN Ia host galaxies. In this work, we present an independent detailed analysis of the Cepheids in NGC 5584. We employ different tools for our photometric analysis and a completely different method for our light-curve analysis, and we do not find a systematic difference between our period and mean magnitude measurements compared to those reported by SH0ES. By adopting a period–luminosity relation calibrated by the Cepheids in the Milky Way, we measure a distance modulus <jats:italic>μ</jats:italic> = 31.810 ± 0.047 (mag), which is in agreement with <jats:italic>μ</jats:italic> = 31.786 ± 0.046 (mag) measured by SH0ES. In addition, the relations we find between the periods and amplitude ratios of the Cepheids in NGC 5584 are significantly tighter than those of SH0ES, and their potential impact on the direct <jats:italic>H</jats:italic> <jats:sub>0</jats:sub> measurement will be investigated in future studies.</jats:p>