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<jats:title>Abstract</jats:title> <jats:p>Asymptotic giant branch stars create a rich inventory of molecules in their envelopes as they lose mass during later stages of their evolution. These molecules cannot survive the conditions in interstellar space, where they are exposed to ultraviolet photons of the interstellar radiation field. As a result, daughter molecules are the ones injected into space, and a halo of those molecules is predicted to exist around cool evolved stars. The most abundant molecule in the envelopes other than H<jats:sub>2</jats:sub> is CO, which dissociates into C that is rapidly ionized into C<jats:sup>+</jats:sup> in a halo around the star that is optically thin to the interstellar radiation field. We develop the specific predictions of the ionized carbon halo size and column density for the well-studied, nearby star IRC+10216. We compare those models to observations of the [C <jats:sc>ii</jats:sc>] 157.7 <jats:italic>μ</jats:italic>m far-infrared fine structure line using the Stratospheric Observatory for Infrared Astronomy and Herschel. The combination of bright emission toward the star and upper limits to extended [C <jats:sc>ii</jats:sc>] is inconsistent with any standard model. The presence of [C <jats:sc>ii</jats:sc>] toward the star requires some dissociation and ionization in the inner part of the outflow, possibly due to a hot companion star. The lack of extended [C <jats:sc>ii</jats:sc>] emission requires that daughter products from CO photodissociation in the outer envelope remain cold. The [C <jats:sc>ii</jats:sc>] profile toward the star is asymmetric, with the blueshifted absorption due to the cold outer envelope.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>The MAMMOTH–Grism slitless spectroscopic survey is a Hubble Space Telescope (HST) cycle 28 medium program, which is obtaining 45 orbits of WFC3/IR grism spectroscopy in the density peak regions of three massive galaxy protoclusters at <jats:italic>z</jats:italic> = 2–3 discovered using the MAMMOTH technique. We introduce this survey by presenting the first measurement of the mass–metallicity relation (MZR) at high redshift in overdense environments via grism spectroscopy. From the completed MAMMOTH–Grism observations in the field of the BOSS1244 protocluster at <jats:italic>z</jats:italic> = 2.24 ± 0.02, we secure a sample of 36 protocluster member galaxies at <jats:italic>z</jats:italic> ≈ 2.24, showing strong nebular emission lines ([O <jats:sc>III</jats:sc>], H<jats:italic>β</jats:italic>, and [O <jats:sc>II</jats:sc>]) in their G141 spectra. Using the multi-wavelength broadband deep imaging from HST and ground-based telescopes, we measure their stellar masses in the range of [10<jats:sup>9</jats:sup>, 10<jats:sup>10.4</jats:sup>] <jats:italic>M</jats:italic> <jats:sub>⊙</jats:sub>, instantaneous star formation rates (SFR) from 10 to 240 <jats:italic>M</jats:italic> <jats:sub>⊙</jats:sub> yr<jats:sup>−1</jats:sup>, and global gas-phase metallicities <jats:inline-formula> <jats:tex-math> <?CDATA $[\tfrac{1}{3},1]$?> </jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mo stretchy="false">[</mml:mo> <mml:mstyle displaystyle="false"> <mml:mfrac> <mml:mrow> <mml:mn>1</mml:mn> </mml:mrow> <mml:mrow> <mml:mn>3</mml:mn> </mml:mrow> </mml:mfrac> </mml:mstyle> <mml:mo>,</mml:mo> <mml:mn>1</mml:mn> <mml:mo stretchy="false">]</mml:mo> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjac3974ieqn1.gif" xlink:type="simple" /> </jats:inline-formula> of solar. Compared with similarly selected field-galaxy samples at the same redshift, our galaxies show, on average, increased SFRs by ∼0.06 dex and ∼0.18 dex at ∼10<jats:sup>10.1</jats:sup> <jats:italic>M</jats:italic> <jats:sub>⊙</jats:sub> and ∼10<jats:sup>9.8</jats:sup> <jats:italic>M</jats:italic> <jats:sub>⊙</jats:sub>, respectively. Using the stacked spectra of our sample galaxies, we derive the MZR in the BOSS1244 protocluster core as <jats:inline-formula> <jats:tex-math> <?CDATA $12+\mathrm{log}({\rm{O}}/{\rm{H}})=\left(0.136\pm 0.018\right)$?> </jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mn>12</mml:mn> <mml:mo>+</mml:mo> <mml:mi>log</mml:mi> <mml:mo stretchy="false">(</mml:mo> <mml:mi mathvariant="normal">O</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:mo>=</mml:mo> <mml:mfenced close=")" open="("> <mml:mrow> <mml:mn>0.136</mml:mn> <mml:mo>±</mml:mo> <mml:mn>0.018</mml:mn> </mml:mrow> </mml:mfenced> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjac3974ieqn2.gif" xlink:type="simple" /> </jats:inline-formula> × <jats:inline-formula> <jats:tex-math> <?CDATA $\mathrm{log}({M}_{* }/{M}_{\odot })+\left(7.082\pm 0.175\right)$?> </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:mfenced close=")" open="("> <mml:mrow> <mml:mn>7.082</mml:mn> <mml:mo>±</mml:mo> <mml:mn>0.175</mml:mn> </mml:mrow> </mml:mfenced> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjac3974ieqn3.gif" xlink:type="simple" /> </jats:inline-formula>, showing a significantly shallower slope than that in the field. This shallow MZR slope is likely caused by the combined effects of efficient recycling of feedback-driven winds and cold-mode gas accretion in protocluster environments. The former effect helps low-mass galaxies residing in overdensities retain their metal production, whereas the latter effect dilutes the metal content of high-mass galaxies, making them more metal-poor than their coeval field counterparts.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Multiwavelength high-resolution imaging of protoplanetary disks has revealed the presence of multiple, varied substructures in their dust and gas components, which might be signposts of young, forming planetary systems. AB Aurigae bears an emblematic (pre)transitional disk showing spiral structures observed in the inner cavity of the disk in both the submillimeter (Atacama Large Millimeter/submillimeter Array (ALMA); 1.3 mm, <jats:sup>12</jats:sup>CO) and near-infrared (Spectro-polarimetric High-contrast Exoplanet Research; 1.5–2.5 <jats:italic>μ</jats:italic>m) wavelengths, which have been claimed to arise from dynamical interactions with a massive companion. In this work, we present new deep <jats:italic>K</jats:italic> <jats:sub>s</jats:sub> (2.16 <jats:italic>μ</jats:italic>m) and <jats:italic>L</jats:italic>′ (3.7 <jats:italic>μ</jats:italic>m) band images of AB Aurigae obtained with the L/M-band Infrared Camera on the Large Binocular Telescope, aimed for the detection of both planetary companions and extended disk structures. No point source is recovered, in particular at the outer regions of the disk, where a putative candidate (<jats:italic>ρ</jats:italic> = 0.″681, PA = 7.°6) had been previously claimed. The nature of a second innermost planet candidate (<jats:italic>ρ</jats:italic> = 0.″16, PA = 203.°9) cannot be investigated by the new data. We are able to derive 5<jats:italic>σ</jats:italic> detection limits in both magnitude and mass for the system, going from 14 <jats:italic>M</jats:italic> <jats:sub>Jup </jats:sub> at 0.″3 (49 au) down to 3–4 <jats:italic>M</jats:italic> <jats:sub>Jup </jats:sub> at 0.″6 (98 au) and beyond, based on the ATMO 2020 evolutionary models. We detect the inner spiral structures (&lt;0.″5) resolved in both CO and polarimetric <jats:italic>H</jats:italic>-band observations. We also recover the ring structure of the system at larger separation (0.″5–0.″7) showing a clear southeast/northwest asymmetry. This structure, observed for the first time at <jats:italic>L</jats:italic>′ band, remains interior to the dust cavity seen at ALMA, suggesting an efficient dust trapping mechanism at play in the disk.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Planets with a few percent water by mass may have a high-pressure ice mantle separating the rocky interior from both the ocean and atmosphere. Here we examine whether the partitioning of O<jats:sub>2</jats:sub> into high-pressure ice can constrain the atmospheric abundance of O<jats:sub>2</jats:sub> produced by water photolysis in the atmosphere. We find that the partition coefficient of dissolved O<jats:sub>2</jats:sub> between high-pressure ice and liquid water is about unity. We show that the solubility of O<jats:sub>2</jats:sub> in high-pressure water ice yields an upper value for the atmospheric abundance of O<jats:sub>2</jats:sub> that depends on the ocean surface temperature. The atmospheric pressure of O<jats:sub>2</jats:sub> has a maximum of approximately 3000 bars. The latter drops to a few hundred bars as the surface temperature of the ocean approaches supercritical conditions.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>The radio radiation mechanism is one of the open questions in pulsar physics. Multiband observations are very important for constraining the pulsar radiation mechanism. In this paper, we investigate the pulse profiles of PSR B1737+13 and its evolution with the frequency. The integrated pulse profiles are obtained from the European Pulsar Network and the Australia Telescope National Facility data, together with recent observations from the largest dish Five-hundred-meter Aperture Spherical radio Telescope. The radiation components are separated with the squared hyperbolic secant functions, and the radiation altitudes of each radiation component at different frequencies are calculated. It is found that the radio radiation at different frequencies comes from different altitudes. The frequency evolutions of separations for the inner and outer cone components are studied. It is found that the separations of the inner and outer cone components have opposite frequency dependence. We simulate the RFM of PSR B1737+13 with the inverse Compton scattering (ICS) model and find that the RFM can be naturally described by the ICS model. Through the simulation, the radio radiation region of PSR B1737+13 is determined, and the result shows that the radio radiation of this pulsar may be generated in the annular gap region.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>We explore the viable <jats:italic>f</jats:italic>(<jats:italic>R</jats:italic>) gravity models in FLRW backgrounds with a free spatial curvature parameter Ω<jats:sub> <jats:italic>K</jats:italic> </jats:sub>. In our numerical calculation, we concentrate on the exponential <jats:italic>f</jats:italic>(<jats:italic>R</jats:italic>) model of <jats:inline-formula> <jats:tex-math> <?CDATA $f(R)=R-\lambda {R}_{\mathrm{ch}}(1-\exp (-R/{R}_{\mathrm{ch}}))$?> </jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mi>f</mml:mi> <mml:mo stretchy="false">(</mml:mo> <mml:mi>R</mml:mi> <mml:mo stretchy="false">)</mml:mo> <mml:mo>=</mml:mo> <mml:mi>R</mml:mi> <mml:mo>−</mml:mo> <mml:mi>λ</mml:mi> <mml:msub> <mml:mrow> <mml:mi>R</mml:mi> </mml:mrow> <mml:mrow> <mml:mi>ch</mml:mi> </mml:mrow> </mml:msub> <mml:mo stretchy="false">(</mml:mo> <mml:mn>1</mml:mn> <mml:mo>−</mml:mo> <mml:mi>exp</mml:mi> <mml:mo stretchy="false">(</mml:mo> <mml:mo>−</mml:mo> <mml:mi>R</mml:mi> <mml:mrow> <mml:mo stretchy="true">/</mml:mo> </mml:mrow> <mml:msub> <mml:mrow> <mml:mi>R</mml:mi> </mml:mrow> <mml:mrow> <mml:mi>ch</mml:mi> </mml:mrow> </mml:msub> <mml:mo stretchy="false">)</mml:mo> <mml:mo stretchy="false">)</mml:mo> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjac4495ieqn1.gif" xlink:type="simple" /> </jats:inline-formula>, where <jats:italic>R</jats:italic> <jats:sub>ch</jats:sub> is the characteristic curvature scale, which is independent of Ω<jats:sub> <jats:italic>K</jats:italic> </jats:sub>, and <jats:italic>λ</jats:italic> corresponds to the model parameter, while <jats:italic>R</jats:italic> <jats:sub>ch</jats:sub> <jats:italic>λ</jats:italic> = 2Λ with Λ the cosmological constant. In particular, we study the evolutions of the dark energy density and equation of state for exponential <jats:italic>f</jats:italic>(<jats:italic>R</jats:italic>) gravity in open, flat, and closed universes, and compare with those for ΛCDM. From the current observational data, we find that <jats:inline-formula> <jats:tex-math> <?CDATA ${\lambda }^{-1}={0.42927}_{-0.32927}^{+0.39921}$?> </jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msup> <mml:mrow> <mml:mi>λ</mml:mi> </mml:mrow> <mml:mrow> <mml:mo>−</mml:mo> <mml:mn>1</mml:mn> </mml:mrow> </mml:msup> <mml:mo>=</mml:mo> <mml:msubsup> <mml:mrow> <mml:mn>0.42927</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>−</mml:mo> <mml:mn>0.32927</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>+</mml:mo> <mml:mn>0.39921</mml:mn> </mml:mrow> </mml:msubsup> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjac4495ieqn2.gif" xlink:type="simple" /> </jats:inline-formula> at 68% C.L. and <jats:inline-formula> <jats:tex-math> <?CDATA ${{\rm{\Omega }}}_{K}=-{0.00050}_{-0.00414}^{+0.00420}$?> </jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msub> <mml:mrow> <mml:mi mathvariant="normal">Ω</mml:mi> </mml:mrow> <mml:mrow> <mml:mi>K</mml:mi> </mml:mrow> </mml:msub> <mml:mo>=</mml:mo> <mml:mo>−</mml:mo> <mml:msubsup> <mml:mrow> <mml:mn>0.00050</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>−</mml:mo> <mml:mn>0.00414</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>+</mml:mo> <mml:mn>0.00420</mml:mn> </mml:mrow> </mml:msubsup> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjac4495ieqn3.gif" xlink:type="simple" /> </jats:inline-formula> at 95% C.L. in the exponential <jats:italic>f</jats:italic>(<jats:italic>R</jats:italic>) model. By using the Akaike Information Criterion, Bayesian Information Criterion, and Deviance Information Criterion, we conclude that there is no strong preference between the exponential <jats:italic>f</jats:italic>(<jats:italic>R</jats:italic>) gravity and ΛCDM models in the nonflat universe.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>The measurement of the macroscopic properties of a neutron star, whether in binary or in an isolated system, provides us with a key opportunity to place a stringent constraint on its equation of state. In this paper, we perform Bayesian model selection on a wide variety of neutron star equations of state using multi-messenger observations. In particular, (i) we use the mass and tidal deformability measurements from two binary neutron star merger events, GW170817 and GW190425; and (ii) we use the simultaneous mass–radius measurements of PSR J0030+0451 and PSR J0740+6620 by the NICER collaboration, while the latter has been analyzed by the joint NICER/radio/XMM-Newton collaboration. Among the 31 equations of state considered in this analysis, we are able to rule out different variants of the MS1 family, SKI5, H4, and WFF1 decisively, which are either extremely stiff or soft equations of state. The most preferred equation of state model turns out to be AP3 (or MPA1), which predicts the radius and dimensionless tidal deformability of a 1.4 <jats:italic>M</jats:italic> <jats:sub>⊙</jats:sub> neutron star to be 12.10 (12.50) km and 393 (513), respectively.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>We present the environmental properties around high-<jats:italic>z</jats:italic> radio galaxies (HzRGs) at <jats:italic>z</jats:italic> ∼ 4, which have been poorly investigated because of their rarity. We use the largest samples of HzRGs and <jats:italic>g</jats:italic>-dropout galaxy overdense regions at <jats:italic>z</jats:italic> ∼ 4, which were constructed from the Hyper Suprime-Cam Subaru Strategic Program, to characterize the HzRG environments statistically. We measure the <jats:italic>g</jats:italic>-dropout galaxy overdensities around 21 HzRGs whose rest-frame 1.4 GHz radio luminosities (<jats:italic>L</jats:italic> <jats:sub>1.4 GHz</jats:sub>) are 10<jats:sup>26–27</jats:sup> W Hz<jats:sup>−1</jats:sup>. We find that the overdensities around the faint HzRGs with <jats:italic>L</jats:italic> <jats:sub>1.4 GHz</jats:sub> ∼ 10<jats:sup>26.0–26.5</jats:sup> W Hz<jats:sup>−1</jats:sup> tend to be higher than those of the <jats:italic>g</jats:italic>-dropout galaxies. On the other hand, no significant difference of density environments is found between the luminous HzRGs with <jats:italic>L</jats:italic> <jats:sub>1.4 GHz</jats:sub> ∼ 10<jats:sup>26.5–27.0</jats:sup> W Hz<jats:sup>−1</jats:sup> and the <jats:italic>g</jats:italic>-dropout galaxies. The HzRGs are found to occupy more massive halos than <jats:italic>g</jats:italic>-dropout galaxies through a cross-correlation between the HzRGs and <jats:italic>g</jats:italic>-dropout galaxies. This trend is more pronounced in the faint HzRGs. These results are consistent with a scenario where HzRGs get older and more massive as the radio luminosity decreases. The HzRGs are expected to trace the progenitors of Local Cluster halos from their calculated halo mass. In addition, we find that surrounding galaxies tend to distribute along the radio jet major axis of the HzRGs at angular distances of ≲500 physical kpc. Our findings imply the onset of the filamentary structures around the HzRGs at <jats:italic>z</jats:italic> ∼ 4.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>We present deep Hubble Space Telescope (HST) imaging of five faint dwarf galaxies associated with the nearby spiral NGC 253 (D ≈ 3.5 Mpc). Three of these are newly discovered dwarf galaxies, while all five were found in the Panoramic Imaging Survey of Centaurus and Sculptor, a Magellan+Megacam survey to identify faint dwarfs and other substructures in resolved stellar light around massive galaxies outside of the Local Group. Our HST data reach ≳3 magnitudes below the tip of the red giant branch for each dwarf, allowing us to derive their distances, structural parameters, and luminosities. All five systems contain mostly old, metal-poor stellar populations (age ∼12 Gyr, [M/H] ≲ −1.5) and have sizes (<jats:italic>r</jats:italic> <jats:sub> <jats:italic>h</jats:italic> </jats:sub> ∼ 110–3000 pc) and luminosities (<jats:italic>M</jats:italic> <jats:sub> <jats:italic>V</jats:italic> </jats:sub> ∼ −7 to −12 mag) largely consistent with Local Group dwarfs. The three new NGC 253 satellites are among the faintest systems discovered beyond the Local Group. We also use archival H <jats:sc>i</jats:sc> data to place limits on the gas content of our discoveries. Deep imaging surveys such as our program around NGC 253 promise to elucidate the faint end of the satellite luminosity function and its scatter across a range of galaxy masses, morphologies, and environments in the decade to come.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>We report 350 pulsating variable stars found in four DECam fields (∼12 deg<jats:sup>2</jats:sup>) covering the Antlia 2 satellite galaxy. The sample of variables includes 318 RR Lyrae stars and eight anomalous Cepheids in the galaxy. Reclassification of several objects designated previously to be RR Lyrae as anomalous Cepheids get rid of the satellite’s stars intervening along the line of sight. This in turn removes the need for prolific tidal disruption of the dwarf, in agreement with the recently updated proper motion and pericenter measurements based on Gaia EDR3. There are also several bright foreground RR Lyrae stars in the field, and two distant background variables located ∼45 kpc behind Antlia 2. We found RR Lyrae stars over the full search area, suggesting that the galaxy is very large and likely extends beyond our observed area. The mean period of the RR<jats:italic>ab</jats:italic> in Antlia 2 is 0.599 days, while the RR<jats:italic>c</jats:italic> have a mean period of 0.368 days, indicating the galaxy is an Oosterhoff-intermediate system. The distance to Antlia 2 based on the RR Lyrae stars is 124.1 kpc (<jats:italic>μ</jats:italic> <jats:sub>0</jats:sub> = 20.47) with a dispersion of 5.4 kpc. We measured a clear distance gradient along the semimajor axis of the galaxy, with the southeast side of Antlia 2 being ∼13 kpc farther away from the northwest side. This elongation along the line of sight is likely due to the ongoing tidal disruption of Ant 2.</jats:p>