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<jats:title>Abstract</jats:title> <jats:p>Large Sky Area Multi-Object Fiber Spectroscopic Telescope (LAMOST) low- and medium-resolution spectroscopic surveys are important for determination of the orbital parameters and chromospheric activity of extrasolar planet systems. We crossmatched the exoplanet catalog confirmed before 2021 March 11 with the LAMOST DR7 survey to study their properties. There are 1026 targets with exoplanets observed in the LAMOST DR7 low-resolution spectroscopic survey and 158 targets in the medium-resolution spectroscopic survey. We have calculated the equivalent width of the H<jats:italic>α</jats:italic> line and determined their stellar activity. The H<jats:italic>α</jats:italic> and flare intensities are almost constant for the Rossby number Ro ≤ 0.12 in the saturated regime and decrease with increasing Ro in the unsaturated regime. In addition, we searched the flare events of all stars with exoplanets in the Transiting Exoplanet Survey Satellite (TESS), Kepler, and K2 surveys. Among the 733 extrasolar planetary systems observed by TESS, we found 481 flares from 57 stars. For Kepler data, we obtained the light curve of 1699 stars and found 1886 flares from 417 stars. For K2 data, we obtained the light curves of 347 stars and found 467 flares from 89 stars. There were light curves of 361 objects with obvious eclipse observed from the TESS survey. We have fitted their light curves with a high signal-to-noise ratio using the JKTEBOP program, and we reobtained the orbital parameters, such as inclination, radius, and period. In the end, we made a judgment on the habitability of exoplanets of stars with flares.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Energetic neutral atom (ENA) measurements by IBEX reveal that the heliotail comprises an energy-dependent multilobe structure. We examine the heliotail evolution over 11 yr of IBEX observations covering a full solar cycle (SC). We find the following: (1) The heliotail structure persists over the entire SC, comprising three ENA-enhanced and two ENA-suppressed lobes. (2) Lobe sizes and locations are generally stable but exhibit variations in ENA fluxes driven by the SC. (3) Lobe centers follow a cyclic behavior over multiple SC phases, indicating direct signatures of slow and fast solar wind (SW) interactions in the inner heliosheath (IHS). (4) The tilted plane passing through the port–starboard lobes’ centers oscillates in latitude but maintains its tilt from the ecliptic plane, likely a consequence of the interstellar magnetic field draping around the heliosphere. (5) The transition of the central heliotail from a single lobe at ∼1.1 keV to two lobes above ∼2 keV is SC-dependent and directly reflects the IHS plasma properties, i.e., when ENA fluxes from fast SW from the polar coronal holes change over time. (6) The central lobe exhibits a substructure that is enhanced and offset from the downwind direction, possibly indicating an asymmetric ENA emission or an asymmetry in the parent plasma distribution. These results reveal the general stability of the heliotail structure over time and distinct variations in individual lobes’ properties in relation to the SC phases. Furthermore, results show the effects of multiple SC phases in the tail, reflecting different ENA travel times and source histories.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>In a galaxy cluster, the relative spatial distributions of dark matter, member galaxies, gas, and intracluster light (ICL) may connote their mutual interactions over the cluster’s evolution. However, it is a challenging problem to provide a quantitative measure for matching the shapes between two multidimensional scalar distributions. We present a novel methodology, named the weighted overlap coefficient (WOC), to quantify the similarity of two-dimensional spatial distributions. We compare the WOC with a standard method known as the modified Hausdorff distance (MHD) method. We find that our method is robust, and performs well even with the existence of multiple substructures. We apply our methodology to search for a visible component whose spatial distribution resembles that of dark matter. If such a component could be found to trace the dark-matter distribution with high fidelity for more relaxed galaxy clusters, then the similarity of the distributions could also be used as a dynamical stage estimator of the cluster. We apply the method to six galaxy clusters at different dynamical stages, simulated within a GRT simulation, which is an <jats:italic>N</jats:italic>-body simulation using the galaxy replacement technique. Among the various components (stellar particles, galaxies, ICL), the ICL+brightest cluster galaxy (BCG) component most faithfully traced the dark-matter distribution. Among the sample galaxy clusters, the relaxed clusters show stronger similarity in the spatial distribution of the dark matter and ICL+BCG than the dynamically young clusters, while the results of the MHD method show a weaker trend with the dynamical stages.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>The Canadian Hydrogen Intensity Mapping Experiment (CHIME) is a drift scan radio telescope operating across the 400–800 MHz band. CHIME is located at the Dominion Radio Astrophysical Observatory near Penticton, BC, Canada. The instrument is designed to map neutral hydrogen over the redshift range 0.8–2.5 to constrain the expansion history of the universe. This goal drives the design features of the instrument. CHIME consists of four parallel cylindrical reflectors, oriented north–south, each 100 m × 20 m and outfitted with a 256-element dual-polarization linear feed array. CHIME observes a two-degree-wide stripe covering the entire meridian at any given moment, observing three-quarters of the sky every day owing to Earth’s rotation. An FX correlator utilizes field-programmable gate arrays and graphics processing units to digitize and correlate the signals, with different correlation products generated for cosmological, fast radio burst, pulsar, very long baseline interferometry, and 21 cm absorber back ends. For the cosmology back end, the <jats:inline-formula> <jats:tex-math> <?CDATA ${N}_{\mathrm{feed}}^{2}$?> </jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msubsup> <mml:mrow> <mml:mi>N</mml:mi> </mml:mrow> <mml:mrow> <mml:mi>feed</mml:mi> </mml:mrow> <mml:mrow> <mml:mn>2</mml:mn> </mml:mrow> </mml:msubsup> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjsac6fd9ieqn1.gif" xlink:type="simple" /> </jats:inline-formula> correlation matrix is formed for 1024 frequency channels across the band every 31 ms. A data receiver system applies calibration and flagging and, for our primary cosmological data product, stacks redundant baselines and integrates for 10 s. We present an overview of the instrument, its performance metrics based on the first 3 yr of science data, and we describe the current progress in characterizing CHIME’s primary beam response. We also present maps of the sky derived from CHIME data; we are using versions of these maps for a cosmological stacking analysis, as well as for investigation of Galactic foregrounds.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>The identification of a virial broadening estimator in the quasar UV rest frame suitable for black hole mass computation at high redshift has become an important issue. We compare the H <jats:sc>i</jats:sc> Balmer <jats:sc>H</jats:sc> <jats:italic>β</jats:italic> line width to the ones of two intermediate-ionization lines: the Al <jats:sc>iii</jats:sc> <jats:italic> λ</jats:italic>1860 doublet and the C <jats:sc>iii]</jats:sc> <jats:italic> λ</jats:italic>1909 line, over a wide interval of redshift and luminosity (0 ≲ <jats:italic>z</jats:italic> ≲ 3.5; <jats:inline-formula> <jats:tex-math> <?CDATA $43\lesssim \mathrm{log}L\lesssim 48.5$?> </jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mn>43</mml:mn> <mml:mo>≲</mml:mo> <mml:mi>log</mml:mi> <mml:mi>L</mml:mi> <mml:mo>≲</mml:mo> <mml:mn>48.5</mml:mn> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjsac6fd6ieqn1.gif" xlink:type="simple" /> </jats:inline-formula> [erg s<jats:sup>−1</jats:sup>]), for 48 sources belonging to the quasar population characterized by intermediate to high values of the Eddington ratio (Population A). The present analysis indicates that the line widths of Al <jats:sc>iii</jats:sc> <jats:italic> λ</jats:italic>1860 and <jats:sc>H</jats:sc> <jats:italic>β</jats:italic> are highly correlated and can be considered equivalent for most Population A quasars over five orders of magnitude in luminosity; for C <jats:sc>iii]</jats:sc> <jats:italic> λ</jats:italic>1909, multiplication by a constant correction factor <jats:italic>ξ</jats:italic> ≈ 1.25 is sufficient to bring the FWHM of C <jats:sc>iii]</jats:sc> in agreement with that of <jats:sc>H</jats:sc> <jats:italic>β</jats:italic>. The statistical concordance between low-ionization and intermediate-ionization lines suggests that they predominantly arise from the same virialized part of the broad-line region. However, blueshifts of modest amplitude (few hundred kilometers per second) with respect to the quasar rest frame and an excess (≲1.1) Al <jats:sc>iii</jats:sc> broadening with respect to <jats:sc>H</jats:sc> <jats:italic>β</jats:italic> are found in a fraction of our sample. Scaling laws to estimate <jats:italic>M</jats:italic> <jats:sub>BH</jats:sub> of high-redshift quasars using the Al <jats:sc>iii</jats:sc> and C <jats:sc>iii]</jats:sc> line widths have rms scatter ≈0.3 dex. The Al <jats:sc>iii</jats:sc> scaling law takes the form <jats:inline-formula> <jats:tex-math> <?CDATA $\mathrm{log}{M}_{\mathrm{BH}}\approx 0.58\mathrm{log}{L}_{\mathrm{1700,44}}+2\mathrm{logFWHM}+0.49$?> </jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mi>log</mml:mi> <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:mn>0.58</mml:mn> <mml:mi>log</mml:mi> <mml:msub> <mml:mrow> <mml:mi>L</mml:mi> </mml:mrow> <mml:mrow> <mml:mn>1700,44</mml:mn> </mml:mrow> </mml:msub> <mml:mo>+</mml:mo> <mml:mn>2</mml:mn> <mml:mi>logFWHM</mml:mi> <mml:mo>+</mml:mo> <mml:mn>0.49</mml:mn> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjsac6fd6ieqn2.gif" xlink:type="simple" /> </jats:inline-formula> [<jats:italic>M</jats:italic> <jats:sub>⊙</jats:sub>].</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Far-ultraviolet (FUV; ∼1200–2000 Å) spectra are fundamental to our understanding of star-forming galaxies, providing a unique window on massive stellar populations, chemical evolution, feedback processes, and reionization. The launch of the James Webb Space Telescope will soon usher in a new era, pushing the UV spectroscopic frontier to higher redshifts than ever before; however, its success hinges on a comprehensive understanding of the massive star populations and gas conditions that power the observed UV spectral features. This requires a level of detail that is only possible with a combination of ample wavelength coverage, signal-to-noise, spectral-resolution, and sample diversity that has not yet been achieved by any FUV spectral database. We present the Cosmic Origins Spectrograph Legacy Spectroscopic Survey (CLASSY) treasury and its first high-level science product, the CLASSY atlas. CLASSY builds on the Hubble Space Telescope (HST) archive to construct the first high-quality (S/N<jats:sub>1500 Å</jats:sub> ≳ 5/resel), high-resolution (<jats:italic>R</jats:italic> ∼ 15,000) FUV spectral database of 45 nearby (0.002 &lt; <jats:italic>z</jats:italic> &lt; 0.182) star-forming galaxies. The CLASSY atlas, available to the public via the CLASSY website, is the result of optimally extracting and coadding 170 archival+new spectra from 312 orbits of HST observations. The CLASSY sample covers a broad range of properties including stellar mass (6.2 &lt; log <jats:italic>M</jats:italic> <jats:sub>⋆</jats:sub>(<jats:italic>M</jats:italic> <jats:sub>⊙</jats:sub>) &lt; 10.1), star formation rate (−2.0 &lt; log SFR (<jats:italic>M</jats:italic> <jats:sub>⊙</jats:sub> yr<jats:sup>−1</jats:sup>) &lt; +1.6), direct gas-phase metallicity (7.0 &lt; 12+log(O/H) &lt; 8.8), ionization (0.5 &lt; O<jats:sub>32</jats:sub> &lt; 38.0), reddening (0.02 &lt; <jats:italic>E</jats:italic>(<jats:italic>B</jats:italic> − <jats:italic>V</jats:italic>) &lt; 0.67), and nebular density (10 &lt; <jats:italic>n</jats:italic> <jats:sub> <jats:italic>e</jats:italic> </jats:sub> (cm<jats:sup>−3</jats:sup>) &lt; 1120). CLASSY is biased to UV-bright star-forming galaxies, resulting in a sample that is consistent with the <jats:italic>z</jats:italic> ∼ 0 mass–metallicity relationship, but is offset to higher star formation rates by roughly 2 dex, similar to <jats:italic>z</jats:italic> ≳ 2 galaxies. This unique set of properties makes the CLASSY atlas the benchmark training set for star-forming galaxies across cosmic time.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Quasars behind the Galactic plane (GPQs) are important astrometric references and valuable probes of Galactic gas, yet the search for GPQs is difficult due to severe extinction and source crowding in the Galactic plane. In this paper, we present a sample of 204 spectroscopically confirmed GPQs at ∣<jats:italic>b</jats:italic>∣ &lt; 20°, 191 of which are new discoveries. This GPQ sample covers a wide redshift range from 0.069 to 4.487. For the subset of 230 observed GPQ candidates, the lower limit of the purity of quasars is 85.2%, and the lower limit of the fraction of stellar contaminants is 6.1%. Using a multicomponent spectral fitting, we measure the emission line and continuum flux of the GPQs, and estimate their single-epoch virial black hole masses. Due to selection effects raised from Galactic extinction and target magnitude, these GPQs have higher black hole masses and continuum luminosities in comparison to the SDSS DR7 quasar sample. The spectral-fitting results and black hole mass estimates are compiled into a main spectral catalog, and an extended spectral catalog of GPQs. The successful identifications prove the reliability of both our GPQ selection methods and the GPQ candidate catalog, shedding light on the astrometric and astrophysical programs that make use of a large sample of GPQs in the future.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>RR Lyrae stars are useful chemical tracers thanks to the empirical relationship between their heavy-element abundance and the shape of their light curves. However, the consistent and accurate calibration of this relation across multiple photometric wave bands has been lacking. We have devised a new method for the metallicity estimation of fundamental-mode RR Lyrae stars in the Gaia optical <jats:italic>G</jats:italic> and near-infrared VISTA <jats:italic>K</jats:italic> <jats:sub> <jats:italic>s</jats:italic> </jats:sub> wave bands by deep learning. First, an existing metallicity prediction method is applied to large photometric data sets, which are then used to train long short-term memory recurrent neural networks for the regression of the [Fe/H] to the light curves in other wave bands. This approach allows an unbiased transfer of our accurate, spectroscopically calibrated <jats:italic>I</jats:italic>-band formula to additional bands at the expense of minimal additional noise. We achieve a low mean absolute error of 0.1 dex and high <jats:italic>R</jats:italic> <jats:sup>2</jats:sup> regression performance of 0.84 and 0.93 for the <jats:italic>K</jats:italic> <jats:sub> <jats:italic>s</jats:italic> </jats:sub> and <jats:italic>G</jats:italic> bands, respectively, measured by cross-validation. The resulting predictive models are deployed on the Gaia DR2 and VVV inner bulge RR Lyrae catalogs. We estimate mean metallicities of −1.35 dex for the inner bulge and −1.7 dex for the halo, which are significantly less than the values obtained by earlier photometric prediction methods. Using our results, we establish a public catalog of photometric metallicities of over 60,000 Galactic RR Lyrae stars and provide an all-sky map of the resulting RR Lyrae metallicity distribution. The software code used for training and deploying our recurrent neural networks is made publicly available in the open-source domain.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>We present a study of the bulge-to-total ratio (B/T) of a <jats:italic>K</jats:italic>s-band-selected sample of 88 close major-merger pairs of galaxies (H-KPAIR), based on two-dimensional decompositions of SDSS <jats:italic>r</jats:italic>-band images with <jats:sc>galfit</jats:sc>. We investigate the dependence of the interaction-induced specific star formation rate enhancement (sSFR<jats:sub>enh</jats:sub>) on the B/T ratio, and the effects of this dependence on the differences between star-forming galaxies (SFGs) in spiral+spiral (S+S) and spiral+elliptical (S+E) pairs. Of all the 132 spiral galaxies in H-KPAIR, the 44 in S+E pairs show higher B/T than those in the 44 S+S pairs, with means of B/T = 0.35 ± 0.05 and B/T = 0.26 ± 0.03, respectively. There is a strong negative dependence of sSFR<jats:sub>enh</jats:sub> on the B/T ratio, and only paired SFGs with B/T &lt; 0.3 show significant (&gt;5<jats:italic>σ</jats:italic>) enhancement. Paired SFGs in S+S pairs show a similar trend, and many disky SFGs (B/T &lt; 0.1) in S+S pairs have strong sSFR enhancements (sSFR<jats:sub>enh</jats:sub> &gt; 0.7 dex). For SFGs in S+E pairs, the sSFR has no clear B/T dependence, nor any significant enhancement in any B/T bin. Disky SFGs in S+S pairs show significant (&gt;4<jats:italic>σ</jats:italic>) enhancement in molecular gas content (<jats:inline-formula> <jats:tex-math> <?CDATA ${M}_{{{\rm{H}}}_{2}}/{M}_{\mathrm{star}}$?> </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: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:msub> <mml:mrow> <mml:mi>M</mml:mi> </mml:mrow> <mml:mrow> <mml:mi>star</mml:mi> </mml:mrow> </mml:msub> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjsac73ecieqn1.gif" xlink:type="simple" /> </jats:inline-formula>), while SFGs in S+E pairs have no such enhancement in any B/T bin. No significant enhancement of the total gas content (<jats:italic>M</jats:italic> <jats:sub>gas</jats:sub>/<jats:italic>M</jats:italic> <jats:sub>star</jats:sub>) is found in any B/T bin for paired galaxies. The star formation efficiency of either the total gas (SFE<jats:sub>gas</jats:sub> = SFR/<jats:italic>M</jats:italic> <jats:sub>gas</jats:sub>) or molecular gas (<jats:inline-formula> <jats:tex-math> <?CDATA ${\mathrm{SFE}}_{{{\rm{H}}}_{2}}=\mathrm{SFR}/{M}_{{{\rm{H}}}_{2}}$?> </jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msub> <mml:mrow> <mml:mi>SFE</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:mo>=</mml:mo> <mml:mi>SFR</mml:mi> <mml:mrow> <mml:mo stretchy="true">/</mml:mo> </mml:mrow> <mml:msub> <mml:mrow> <mml:mi>M</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:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjsac73ecieqn2.gif" xlink:type="simple" /> </jats:inline-formula>) does not depend on the B/T ratio. The only significant (&gt; 4<jats:italic>σ</jats:italic>) SFE enhancement found for paired SFGs is the SFE<jats:sub>gas</jats:sub> for disky SFGs in S+S pairs.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>High-resolution spectra of singly ionized nickel (Ni <jats:sc>ii</jats:sc>) have been recorded using Fourier transform spectroscopy in the region 143–5555 nm (1800–70,000 cm<jats:sup>−1</jats:sup>) with continuous, nickel–helium hollow cathode discharge sources. An extensive analysis of identified Ni <jats:sc>ii</jats:sc> lines resulted in the confirmation and revision of 283 previously reported energy levels, from the ground state up to the 3<jats:italic>d</jats:italic> <jats:sup>8</jats:sup>(<jats:sup> <jats:italic>M</jats:italic> </jats:sup> <jats:italic>L</jats:italic>)6<jats:italic>s</jats:italic> subconfigurations. Typical energy-level uncertainties are a few thousandths of a cm<jats:sup>−1</jats:sup>, representing at least an order-of-magnitude reduction in uncertainty with respect to previous measurements. Twenty-five new energy levels have now been established and are reported here for the first time. Eigenvector compositions of the energy levels have been calculated using the orthogonal operator method. In total, 159 even and 149 odd energy levels and 1424 classified line wavelengths of Ni <jats:sc>ii</jats:sc> are reported and will enable more accurate and reliable analyses of Ni <jats:sc>ii</jats:sc> in astrophysical spectra.</jats:p>