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<jats:title>Abstract</jats:title> <jats:p>The decay of sunspot groups is a relatively unknown field since most studies have focused mainly on the decay of sunspots or sunspot groups, but only on small samples. As an extension of the recent work of Muraközy (2020), which is based on a large verified sample, this study investigates not only the long-term behavior of the decay of sunspot groups but also the dynamics of their parts. The aim of the present work is to search for dependencies of the decay process in order to find physical conditions that modify or contribute to the decay. The investigations are based on the catalog of the SoHO Debrecen Sunspot Database (SDD) and the Greenwich Photoheliographic Results as well as the Debrecen Photoheliographic Data. Altogether more than 750 sunspot groups were considered. The decay rates have been calculated for the total, umbral, and penumbral area of the groups and in the case of the SDD’s groups they have been calculated for both the leading and the following parts. The decay rates depend linearly on the maximum areas and ranged from 30 to 50 millionths of the solar hemisphere (MSH) day<jats:sup>−1</jats:sup> for the sunspot groups and penumbrae and 5–10 MSH day<jats:sup>−1</jats:sup> for the umbrae throughout the cycle. The decay rates fall significantly during the Gnevyshev gap and show 4 + 4 Schwabe cyclical variations in the ascending/descending phases, but it is always higher in the northern hemisphere. There is a slight decrease in the decay rates in the activity range toward higher latitudes.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>We investigate the nature of the relations between black hole (BH) mass (<jats:italic>M</jats:italic> <jats:sub>BH</jats:sub>) and the central velocity dispersion (<jats:italic>σ</jats:italic>) and, for core-Sérsic galaxies, the size of the depleted core (<jats:italic>R</jats:italic> <jats:sub>b</jats:sub>). Our sample of 144 galaxies with dynamically determined <jats:italic>M</jats:italic> <jats:sub>BH</jats:sub> encompasses 24 core-Sérsic galaxies, thought to be products of gas-poor mergers, and reliably identified based on high-resolution Hubble Space Telescope imaging. For core-Sérsic galaxies, i.e., combining normal-core (<jats:italic>R</jats:italic> <jats:sub>b</jats:sub> &lt; 0.5 kpc) and large-core galaxies (<jats:italic>R</jats:italic> <jats:sub>b</jats:sub> ≳ 0.5 kpc), we find that <jats:italic>M</jats:italic> <jats:sub>BH</jats:sub> correlates remarkably well with <jats:italic>R</jats:italic> <jats:sub>b</jats:sub> such that <jats:inline-formula> <jats:tex-math> <?CDATA ${M}_{\mathrm{BH}}\propto {R}_{{\rm{b}}}^{1.20\pm 0.14}$?> </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>BH</mml:mi> </mml:mrow> </mml:msub> <mml:mo>∝</mml:mo> <mml:msubsup> <mml:mrow> <mml:mi>R</mml:mi> </mml:mrow> <mml:mrow> <mml:mi mathvariant="normal">b</mml:mi> </mml:mrow> <mml:mrow> <mml:mn>1.20</mml:mn> <mml:mo>±</mml:mo> <mml:mn>0.14</mml:mn> </mml:mrow> </mml:msubsup> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjabceaeieqn1.gif" xlink:type="simple" /> </jats:inline-formula> (rms scatter in log <jats:italic>M</jats:italic> <jats:sub>BH</jats:sub> of Δ<jats:sub>rms</jats:sub> ∼ 0.29 dex), confirming previous works on the same galaxies apart from three new ones. Separating the sample into Sérsic, normal-core and large-core galaxies, we find that Sérsic and normal-core galaxies jointly define a single log-linear <jats:italic>M</jats:italic> <jats:sub>BH</jats:sub>–<jats:italic>σ</jats:italic> relation <jats:italic>M</jats:italic> <jats:sub>BH</jats:sub> ∝ <jats:italic>σ</jats:italic> <jats:sup>4.88±0.29</jats:sup> with Δ<jats:sub>rms</jats:sub> ∼ 0.47 dex; however, at the high-mass end, large-core galaxies (four with measured <jats:italic>M</jats:italic> <jats:sub>BH</jats:sub>) are offset upward from this relation by (2.5–4) × <jats:italic>σ</jats:italic> <jats:sub>s</jats:sub>, explaining the previously reported steepening of the <jats:italic>M</jats:italic> <jats:sub>BH</jats:sub>–<jats:italic>σ</jats:italic> relation for massive galaxies. Large-core spheroids have magnitudes <jats:italic>M</jats:italic> <jats:sub> <jats:italic>V</jats:italic> </jats:sub> ≲ −23.50 mag, half-light radii <jats:italic>R</jats:italic> <jats:sub>e</jats:sub> ≳ 10 kpc, and are extremely massive, <jats:italic>M</jats:italic> <jats:sub>*</jats:sub> ≳ 10<jats:sup>12</jats:sup> <jats:italic>M</jats:italic> <jats:sub>☉</jats:sub>. Furthermore, these spheroids tend to host ultramassive BHs (<jats:italic>M</jats:italic> <jats:sub>BH</jats:sub> ≳ 10<jats:sup>10</jats:sup> <jats:italic>M</jats:italic> <jats:sub>☉</jats:sub>) tightly connected with their <jats:italic>R</jats:italic> <jats:sub>b</jats:sub> rather than <jats:italic>σ</jats:italic>. The less popular <jats:italic>M</jats:italic> <jats:sub>BH</jats:sub>–<jats:italic>R</jats:italic> <jats:sub>b</jats:sub> relation exhibits ∼62% less scatter in log <jats:italic>M</jats:italic> <jats:sub>BH</jats:sub> than the <jats:italic>M</jats:italic> <jats:sub>BH</jats:sub>–<jats:italic>σ</jats:italic> relations. Our findings suggest that large-core spheroids form via multiple major “dry” merger events involving super/ultramassive BHs, consistent with the flattening of the <jats:italic>σ</jats:italic>–<jats:italic>L</jats:italic> <jats:sub> <jats:italic>V</jats:italic> </jats:sub> relation observed at <jats:italic>M</jats:italic> <jats:sub> <jats:italic>V</jats:italic> </jats:sub> ≲ −23.5 mag.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>We examine the Fundamental Plane (FP) and mass-to-light ratio (<jats:italic>M</jats:italic>/<jats:italic>L</jats:italic>) scaling relations using the largest sample of massive quiescent galaxies at 1.5 &lt; <jats:italic>z</jats:italic> &lt; 2.5 to date. The FP (<jats:italic>r</jats:italic> <jats:sub> <jats:italic>e</jats:italic> </jats:sub>, <jats:italic>σ</jats:italic> <jats:sub> <jats:italic>e</jats:italic> </jats:sub>, <jats:italic>I</jats:italic> <jats:sub> <jats:italic>e</jats:italic> </jats:sub>) is established using 19 <jats:italic>UVJ</jats:italic> quiescent galaxies from COSMOS with Hubble Space Telescope <jats:italic>H</jats:italic> <jats:sub> <jats:italic>F</jats:italic>160<jats:italic>W</jats:italic> </jats:sub> rest-frame optical sizes and X-shooter absorption line-measured stellar velocity dispersions. For a very massive, <jats:inline-formula> <jats:tex-math> <?CDATA $\mathrm{log}({M}_{* }/{M}_{\odot })\gt 11.26$?> </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>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>&gt;</mml:mo> <mml:mn>11.26</mml:mn> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjabce66ieqn1.gif" xlink:type="simple" /> </jats:inline-formula>, subset of eight quiescent galaxies at <jats:italic>z</jats:italic> &gt; 2, from Stockmann et al., we show that they cannot passively evolve to the local Coma cluster relation alone and must undergo significant structural evolution to mimic the sizes of local massive galaxies. The evolution of the FP and <jats:italic>M</jats:italic>/<jats:italic>L</jats:italic> scaling relations, from <jats:italic>z</jats:italic> = 2 to present day, for this subset are consistent with passive aging of the stellar population and minor merger structural evolution into the most massive galaxies in the Coma cluster and other massive elliptical galaxies from the MASSIVE Survey. Modeling the luminosity evolution from minor merger-added stellar populations favors a history of merging with “dry” quiescent galaxies.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Low-energy (∼ MeV) cosmic rays (CRs) ionize molecular clouds and create the neutral iron line (Fe <jats:sc>i</jats:sc> K<jats:italic>α</jats:italic>) at 6.4 keV. On the other hand, high-energy (≳GeV) CRs interact with the dense cloud gas and produce gamma rays. Based on a one-dimensional model, we study the spatial correlation among ionization rates of gas, 6.4 keV line fluxes, and gamma-ray emissions from a molecular cloud illuminated by CRs accelerated at an adjacent supernova remnant. We find that the spatial distributions of these three observables depend on how CRs intrude the cloud and on the internal structure of the cloud. If the intrusion is represented by slow diffusion, the 6.4 keV line should be detected around the cloud edge where ionization rates are high. On the other hand, if CRs freely stream in the cloud, the 6.4 keV line should be observed where gamma rays are emitted. In the former, the cooling time of the CRs responsible for the 6.4 keV line is shorter than their cloud crossing time, and it is opposite in the latter. Although we compare the results with observations, we cannot conclude whether the diffusion or the free-streaming is dominantly realized. Our predictions can be checked in more detail with future X-ray missions such as XRISM and Athena and by observations of ionization rates that cover wider fields.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>We present a reanalysis of the Swift Burst Alert Telescope (BAT) data around the radio detection of FRB 131104. Possible evidence of a gamma-ray counterpart was presented by DeLaunay et al. However, based on our analysis using all the available BAT data, no significant emission is found in either the temporal or the image domain. We place a 5<jats:italic>σ</jats:italic> fluence upper limit of 3.3 × 10<jats:sup>−6</jats:sup> erg cm<jats:sup>−2</jats:sup> and 2.7 × 10<jats:sup>−6</jats:sup> erg cm<jats:sup>−2</jats:sup> (15–150 keV) with an integration time of 300 s assuming a simple power-law spectrum with photon index of −1.2 and −2.0, respectively. Our result does not support the association of this FRB with a high-energy counterpart, in agreement with growing observational evidence that most FRBs are not associated with catastrophic events such as gamma-ray bursts.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>The Event Horizon Telescope mass estimate for M87* is consistent with the stellar dynamics mass estimate and inconsistent with the gas-dynamics mass estimates by up to 2<jats:italic>σ</jats:italic>. We have previously explored a new gas-dynamics model that incorporated sub-Keplerian gas velocities and could, in principle, explain the discrepancy in the stellar and gas-dynamics mass estimate. In this paper, we extend this gas-dynamical model to also include non-trivial disk heights, which may also resolve the mass discrepancy independent of sub-Keplerian velocity components. By combining the existing velocity measurements and the Event Horizon Telescope mass estimate, we place constraints on the gas disk inclination and sub-Keplerian fraction. These constraints require the parsec-scale ionized gas disk to be misaligned with the milliarcsecond radio jet by at least 11°, and more typically 27°. Modifications to the gas-dynamics model either by introducing sub-Keplerian velocities or thick disks produce further misalignment with the radio jet. If the jet is produced in a Blandford–Znajek-type process, the angular momentum of the black hole is decoupled with the angular momentum of the large-scale gas feeding M87*.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Time-domain science has undergone a revolution over the past decade, with tens of thousands of new supernovae (SNe) discovered each year. However, several observational domains, including SNe within days or hours of explosion and faint, red transients, are just beginning to be explored. Here we present the Young Supernova Experiment (YSE), a novel optical time-domain survey on the Pan-STARRS telescopes. Our survey is designed to obtain well-sampled <jats:italic>griz</jats:italic> light curves for thousands of transient events up to <jats:italic>z</jats:italic> ≈ 0.2. This large sample of transients with four-band light curves will lay the foundation for the Vera C. Rubin Observatory and the Nancy Grace Roman Space Telescope, providing a critical training set in similar filters and a well-calibrated low-redshift anchor of cosmologically useful SNe Ia to benefit dark energy science. As the name suggests, YSE complements and extends other ongoing time-domain surveys by discovering fast-rising SNe within a few hours to days of explosion. YSE is the only current four-band time-domain survey and is able to discover transients as faint as ∼21.5 mag in <jats:italic>gri</jats:italic> and ∼20.5 mag in <jats:italic>z</jats:italic>, depths that allow us to probe the earliest epochs of stellar explosions. YSE is currently observing approximately 750 deg<jats:sup>2</jats:sup> of sky every 3 days, and we plan to increase the area to 1500 deg<jats:sup>2</jats:sup> in the near future. When operating at full capacity, survey simulations show that YSE will find ∼5000 new SNe per year and at least two SNe within 3 days of explosion per month. To date, YSE has discovered or observed 8.3% of the transient candidates reported to the International Astronomical Union in 2020. We present an overview of YSE, including science goals, survey characteristics, and a summary of our transient discoveries to date.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>An oblique-rotating pulsar generates a relativistic striped wind in a pulsar wind nebula (PWN). The termination shock of the PWN compresses the Poynting-flux-dominated flow and drives magnetic reconnection. By carrying out particle-in-cell simulations of the termination shock of the PWN, we study the shock structure as well as the energy conversion processes and particle acceleration mechanisms. With the recent advances in the numerical methods, we extend the simulations to the ultrarelativistic regime with a bulk Lorentz factor of up to <jats:italic>γ</jats:italic> <jats:sub>0</jats:sub> = 10<jats:sup>6</jats:sup>. Magnetic reconnection at the termination shock is highly efficient at converting magnetic energy to particle kinetic energy and accelerating particles to high energies. Similar to earlier studies, we find that the resulting energy spectra crucially depend on <jats:italic>λ</jats:italic>/<jats:italic>d</jats:italic> <jats:sub> <jats:italic>e</jats:italic> </jats:sub> (<jats:italic>λ</jats:italic> is the wavelength of the striped wind and <jats:italic>d</jats:italic> <jats:sub> <jats:italic>e</jats:italic> </jats:sub> is the relativistic plasma skin depth). When <jats:italic>λ</jats:italic>/<jats:italic>d</jats:italic> <jats:sub> <jats:italic>e</jats:italic> </jats:sub> is large (<jats:italic>λ</jats:italic> ≳ 40<jats:italic>d</jats:italic> <jats:sub> <jats:italic>e</jats:italic> </jats:sub>), the downstream particle spectra form a power-law distribution in the magnetically dominated relativistic wind regime. By analyzing particle trajectories and statistical quantities relevant to particle energization, we find that Fermi-type mechanism dominates the particle acceleration and power-law formation. We find that the results for particle acceleration are scalable as <jats:italic>γ</jats:italic> <jats:sub>0</jats:sub> and <jats:italic>σ</jats:italic> <jats:sub>0</jats:sub> increase to large values. The maximum energy for electrons and positrons can reach hundreds of TeV if the wind has a bulk Lorentz factor of <jats:italic>γ</jats:italic> <jats:sub>0</jats:sub> ≈ 10<jats:sup>6</jats:sup> and a magnetization parameter of <jats:italic>σ</jats:italic> <jats:sub>0</jats:sub> = 10, which can explain the recent observations of high-energy gamma rays from PWNe.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Our understanding of galaxy evolution is derived from large surveys designed to maximize efficiency by only observing the minimum amount needed to infer properties for a typical galaxy. However, for a few percent of galaxies in every survey, these observations are insufficient and derived properties can be catastrophically wrong. Further, it is currently difficult or impossible to determine which objects have failed, so that these contaminate every study of galaxy properties. We develop a novel method to identify these objects by combining the astronomical codes that infer galaxy properties with the dimensionality reduction algorithm t-SNE, which groups similar objects to determine which inferred properties are out of place. This method provides an improvement for the COSMOS catalog, which already uses existing techniques for catastrophic error removal, and therefore should improve the quality of large catalogs and any studies that are sensitive to large redshift errors.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Supernovae (SNe) with photospheric spectra devoid of hydrogen and helium features are generally classified as SNe Ic. However, there is ongoing debate as to whether helium can be hidden in the ejecta of SNe Ic (that is, helium is present in the ejecta, but produces no obvious features in the spectra). We present the first application of the fast, 1D radiative transfer code <jats:sc>tardis</jats:sc> to an SN Ic, and we investigate the question of how much helium can be hidden in the outer layers of the SN Ic ejecta. We generate <jats:sc>tardis</jats:sc> models for the nearby, well-observed, and extensively modeled SN Ic 1994I, and we perform a code comparison to a different, well-established Monte Carlo based radiation transfer code. The code comparison shows that <jats:sc>tardis</jats:sc> produces consistent synthetic spectra for identical ejecta models of SN 1994I. In addition, we perform a systematic experiment of adding outer He shells of varying masses to our SN 1994I models. We find that an outer He shell of only 0.05<jats:italic>M</jats:italic> <jats:sub>⊙</jats:sub> produces strong optical and near-infrared (NIR) He spectral features for SN 1994I which are not present in observations, thus indicating that the SN 1994I ejecta is almost fully He deficient compared to the He masses of typical He-rich SN progenitors. Finally we show that the He <jats:sc>i</jats:sc> <jats:italic>λ</jats:italic>20851 line pseudo-equivalent width of our modeled spectra for SN 1994I could be used to infer the outer He shell mass which suggests that NIR spectral follow-up of SNe Ic will be critical for addressing the hidden helium question for a statistical sample of SNe Ic.</jats:p>