Catálogo de publicaciones - revistas

<jats:title>Abstract</jats:title> <jats:p>This work proposes a residual recurrent neural network (RRNet) for synthetically extracting spectral information and estimating stellar atmospheric parameters together with 15 chemical element abundances for medium-resolution spectra from the Large Sky Area Multi-Object Fiber Spectroscopic Telescope (LAMOST). The RRNet consists of two fundamental modules: a residual module and a recurrent module. The residual module extracts spectral features based on the longitudinally driving power from parameters, while the recurrent module recovers spectral information and restrains the negative influences from noises based on Cross-band Belief Enhancement. RRNet is trained by the spectra from common stars between LAMOST DR7 and the APOGEE-Payne catalog. The 17 stellar parameters and their uncertainties for 2.37 million medium-resolution spectra from LAMOST DR7 are predicted. For spectra with a signal-to-noise ratio ≥ 10, the precision of estimations (<jats:italic>T</jats:italic> <jats:sub>eff</jats:sub> and log <jats:italic>g</jats:italic>) are 88 K and 0.13 dex, respectively, elements C, Mg, Al, Si, Ca, Fe, and Ni are 0.05–0.08 dex, and N, O, S, K, Ti, Cr, and Mn are 0.09–0.14 dex, while that of Cu is 0.19 dex. Compared with StarNet and SPCANet, RRNet shows higher accuracy and robustness. In comparison to Apache Point Observatory Galactic Evolution Experiment and Galactic Archaeology with HERMES surveys, RRNet manifests good consistency within a reasonable range of bias. Finally, this work releases a catalog of 2.37 million medium-resolution spectra from the LAMOST DR7, the source code, the trained model, and the experimental data, respectively, for astronomical science exploration and data-processing algorithm research reference.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>After morphological classification of 18,190 <jats:sup>12</jats:sup>CO molecular clouds, we further investigate the properties of their internal molecular gas structures traced by the <jats:sup>13</jats:sup>CO (<jats:italic>J</jats:italic> = 1−0) line emissions. Using three different methods to extract the <jats:sup>13</jats:sup>CO gas structures within each <jats:sup>12</jats:sup>CO cloud, we find that ∼15% of the <jats:sup>12</jats:sup>CO clouds (2851) have <jats:sup>13</jats:sup>CO gas structures and these <jats:sup>12</jats:sup>CO clouds contribute about 93% of the total integrated flux of <jats:sup>12</jats:sup>CO emission. In each of the 2851 <jats:sup>12</jats:sup>CO clouds with <jats:sup>13</jats:sup>CO gas structures, the <jats:sup>13</jats:sup>CO emission area generally does not exceed 70% of the <jats:sup>12</jats:sup>CO emission area, and the <jats:sup>13</jats:sup>CO integrated flux does not exceed 20% of the <jats:sup>12</jats:sup>CO integrated flux. We reveal a strong correlation between the velocity-integrated intensities of <jats:sup>12</jats:sup>CO lines and those of <jats:sup>13</jats:sup>CO lines in both <jats:sup>12</jats:sup>CO and <jats:sup>13</jats:sup>CO emission regions. This indicates the H<jats:sub>2</jats:sub> column densities of molecular clouds are crucial for the <jats:sup>13</jats:sup>CO line emission. After linking the <jats:sup>13</jats:sup>CO structure detection rates of the 18,190 <jats:sup>12</jats:sup>CO molecular clouds to their morphologies, i.e., nonfilaments and filaments, we find that the <jats:sup>13</jats:sup>CO gas structures are primarily detected in <jats:sup>12</jats:sup>CO clouds with filamentary morphologies. Moreover, these filaments tend to harbor more than one <jats:sup>13</jats:sup>CO structure. That demonstrates filaments not only have larger spatial scales, but also have more molecular gas structures traced by <jats:sup>13</jats:sup>CO lines, i.e., local gas density enhancements. Our results favor the turbulent compression scenario for filament formation, in which dynamical compression of turbulent flows induces local density enhancements. The nonfilaments tend to be in the low-pressure and quiescent turbulent environments of the diffuse interstellar medium.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>We present the second public data release (DR2) from the DECam Local Volume Exploration survey (DELVE). DELVE DR2 combines new DECam observations with archival DECam data from the Dark Energy Survey, the DECam Legacy Survey, and other DECam community programs. DELVE DR2 consists of ∼160,000 exposures that cover &gt;21,000 deg<jats:sup>2</jats:sup> of the high-Galactic-latitude (∣<jats:italic>b</jats:italic>∣ &gt; 10°) sky in four broadband optical/near-infrared filters (<jats:italic>g</jats:italic>, <jats:italic>r</jats:italic>, <jats:italic>i</jats:italic>, <jats:italic>z</jats:italic>). DELVE DR2 provides point-source and automatic aperture photometry for ∼2.5 billion astronomical sources with a median 5<jats:italic>σ</jats:italic> point-source depth of <jats:italic>g</jats:italic> = 24.3, <jats:italic>r</jats:italic> = 23.9, <jats:italic>i</jats:italic> = 23.5, and <jats:italic>z</jats:italic> = 22.8 mag. A region of ∼17,000 deg<jats:sup>2</jats:sup> has been imaged in all four filters, providing four-band photometric measurements for ∼618 million astronomical sources. DELVE DR2 covers more than 4 times the area of the previous DELVE data release and contains roughly 5 times as many astronomical objects. DELVE DR2 is publicly available via the NOIRLab Astro Data Lab science platform.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>We use a high-precision radial velocity survey of FGKM stars to study the conditional occurrence of two classes of planets: close-in small planets (0.023–1 au, 2–30 <jats:italic>M</jats:italic> <jats:sub>⊕</jats:sub>) and distant giant planets (0.23–10 au, 30–6000 <jats:italic>M</jats:italic> <jats:sub>⊕</jats:sub>). We find that <jats:inline-formula> <jats:tex-math> <?CDATA ${41}_{-13}^{+15} \% $?> </jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msubsup> <mml:mrow> <mml:mn>41</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>−</mml:mo> <mml:mn>13</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>+</mml:mo> <mml:mn>15</mml:mn> </mml:mrow> </mml:msubsup> <mml:mo>%</mml:mo> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjsac7230ieqn1.gif" xlink:type="simple" /> </jats:inline-formula> of systems with a close-in, small planet also host an outer giant, compared to <jats:inline-formula> <jats:tex-math> <?CDATA ${17.6}_{-1.9}^{+2.4} \% $?> </jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msubsup> <mml:mrow> <mml:mn>17.6</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>−</mml:mo> <mml:mn>1.9</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>+</mml:mo> <mml:mn>2.4</mml:mn> </mml:mrow> </mml:msubsup> <mml:mo>%</mml:mo> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjsac7230ieqn2.gif" xlink:type="simple" /> </jats:inline-formula> for stars irrespective of small planet presence. This implies that small planet hosts may be enhanced in outer giant occurrences compared to all stars with 1.7<jats:italic>σ</jats:italic> significance. Conversely, we estimate that <jats:inline-formula> <jats:tex-math> <?CDATA ${42}_{-13}^{+17} \% $?> </jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msubsup> <mml:mrow> <mml:mn>42</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>−</mml:mo> <mml:mn>13</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>+</mml:mo> <mml:mn>17</mml:mn> </mml:mrow> </mml:msubsup> <mml:mo>%</mml:mo> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjsac7230ieqn3.gif" xlink:type="simple" /> </jats:inline-formula> of cold giant hosts also host an inner small planet, compared to <jats:inline-formula> <jats:tex-math> <?CDATA ${27.6}_{-4.8}^{+5.8} \% $?> </jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msubsup> <mml:mrow> <mml:mn>27.6</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>−</mml:mo> <mml:mn>4.8</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>+</mml:mo> <mml:mn>5.8</mml:mn> </mml:mrow> </mml:msubsup> <mml:mo>%</mml:mo> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjsac7230ieqn4.gif" xlink:type="simple" /> </jats:inline-formula> of stars irrespective of cold giant presence. We also find that more massive and close-in giant planets are not associated with small inner planets. Specifically, our sample indicates that small planets are less likely to have outer giant companions more massive than approximately 120 <jats:italic>M</jats:italic> <jats:sub>⊕</jats:sub> and within 0.3–3 au, than to have less massive or more distant giant companions, with ∼2.2<jats:italic>σ</jats:italic> confidence. This implies that massive gas giants within 0.3–3 au may suppress inner small planet formation. Additionally, we compare the host-star metallicity distributions for systems with only small planets and those with both small planets and cold giants. In agreement with previous studies, we find that stars in our survey that only host small planets have a metallicity distribution that is consistent with the broader solar-metallicity-median sample, while stars that host both small planets and gas giants are distinctly metal rich with ∼2.3<jats:italic>σ</jats:italic> confidence.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>We searched for diffuse interstellar bands (DIBs) in the 0.91 &lt; <jats:italic>λ</jats:italic> &lt; 1.33 <jats:italic>μ</jats:italic>m region by analyzing the near-infrared (NIR) high-resolution (<jats:italic>R</jats:italic> = 20,000 and 28,000) spectra of 31 reddened early-type stars (0.04 &lt; <jats:italic>E</jats:italic>(<jats:italic>B</jats:italic> − <jats:italic>V</jats:italic>) &lt; 4.58) and an unreddened reference star. The spectra were collected using the WINERED spectrograph, which was mounted on the 1.3 m Araki telescope at Koyama Astronomical Observatory, Japan, in 2012–2016, and on the 3.58 m New Technology Telescope at La Silla Observatory, Chile, in 2017–2018. We detected 54 DIBs—25 of which are newly detected by this study—and eight DIB candidates. Using this updated list, the DIB distributions over a wide wavelength range, from optical to NIR, are investigated. The FWHM values of the NIR DIBs are found to be narrower than those of the optical DIBs, on average, which suggests that the DIBs at longer wavelengths tend to be caused by larger molecules. Assuming that the larger carriers are responsible for the DIBs at longer wavelengths, and have larger oscillator strengths, we found that the total column densities of the DIB carriers tend to decrease with increasing DIB wavelength. The candidate molecules and ions for the NIR DIBs are also discussed.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>We present optical-line gas metallicity diagnostics established by the combination of local SDSS galaxies and the largest compilation of extremely metal-poor galaxies (EMPGs) including new EMPGs identified by the Subaru EMPRESS survey. A total of 103 EMPGs are included, covering a large parameter space of magnitude (<jats:italic>M</jats:italic> <jats:sub> <jats:italic>i</jats:italic> </jats:sub> = −19 to −7) and H<jats:italic>β</jats:italic> equivalent width (10–600 Å), i.e., wide ranges of stellar mass and star formation rate. Using reliable metallicity measurements from the direct method for these galaxies, we derive the relationships between strong optical-line ratios and gas-phase metallicity over the range of <jats:inline-formula> <jats:tex-math> <?CDATA $12+\mathrm{log}({\rm{O}}/{\rm{H}})$?> </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:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjsac7710ieqn1.gif" xlink:type="simple" /> </jats:inline-formula> ≃ 6.9–8.9, corresponding to 0.02–2 solar metallicity <jats:italic>Z</jats:italic> <jats:sub>⊙</jats:sub>. We confirm that the R23 index, ([O <jats:sc>iii</jats:sc>]+[O <jats:sc>ii</jats:sc>])/H<jats:italic>β</jats:italic>, is the most accurate metallicity indicator with a metallicity uncertainty of 0.14 dex over the range among various popular metallicity indicators. The other metallicity indicators show large scatters in the metal-poor range (≲0.1 <jats:italic>Z</jats:italic> <jats:sub>⊙</jats:sub>). It is explained by our <jats:monospace>CLOUDY</jats:monospace> photoionization modeling that, unlike the R23 index, the other metallicity indicators do not use a sum of singly and doubly ionized lines and cannot trace both low- and high-ionization gas. We find that the accuracy of the metallicity indicators is significantly improved if one uses H<jats:italic>β</jats:italic> equivalent width measurements that tightly correlate with ionization states. In this work, we also present the relation of physical properties with the UV-continuum slope <jats:italic>β</jats:italic> and ionization production rate <jats:italic>ξ</jats:italic> <jats:sub>ion</jats:sub> derived with GALEX data for the EMPGs and provide local anchors of galaxy properties together with the optical-line metallicity indicators that are available in the form of a machine-readable table and useful for forthcoming JWST spectroscopic studies.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Highly variable Markarian 421 is a bright high–synchrotron energy peaked blazar showing a wide featureless nonthermal spectrum, making it a good candidate for our study of intraday flux and spectral variations over time. We analyze its X-ray observations over 17 yr, taken with the EPIC-pn instrument, to probe into the intraday variability properties, focusing on the photon energy band of 0.3–10.0 keV, and its soft (0.3–2.0 keV) and hard (2.0–10.0 keV) subbands. To examine the flux variability, fractional variability amplitudes and minimum variability timescales have been calculated. We also probed into the spectral variability by studying the hardness ratio for each observation, the correlation between the two energy bands, using the discrete correlation function, and inspecting the normalized light curves. The parameters obtained from these methods were studied for any correlations or nonrandom trends. From this work, we speculate on the constraints on the possible particle acceleration and emission processes in the jet, for a better understanding of the processes involving turbulent behavior, except for shocks. A positive discrete correlation function between the two subbands indicates the role of the same electron population in the emission of photons in the two bands. A correlation between the parameter of flux variability and the parameters of spectral variation and lags in the subenergy bands provides the constraints to be considered for any modeling of emission processes.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>We present a very large extension of the Galactic plane CO survey of Dame et al. to the entire northern sky (<jats:italic>δ</jats:italic> &gt; −17°). The extension was carried out with the same telescope as was used for the plane survey, the CfA 1.2 m, and perfectly meshes with its irregular boundaries in latitude. A total of 382,202 CO(1–0) spectra uniformly sample the high-latitude sky with a true-angle spacing of 0.°25 or better. The final reduced and folded spectra have a uniform sensitivity of 0.18 K in 0.65 km s<jats:sup>−1</jats:sup> channels and provide a velocity coverage of ±47.1 km s<jats:sup>−1</jats:sup>. We describe the observational techniques and the data reduction and provide various summary maps of the spatial and velocity distributions of CO emission over the northern sky, and a catalog of the molecular clouds we found there. We also describe the CO spectral line data cubes that we have made available online.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>The SDSS-IV MaNGA survey has measured two-dimensional maps of emission-line velocities for a statistically powerful sample of nearby galaxies. The asymmetric features of these kinematics maps reflect the nonrotational component of a galaxy’s internal motion of ionized gas. In this study, we present a catalog of kinematic asymmetry measurements of the H<jats:italic>α</jats:italic> velocity map of a sample of 5353 MaNGA galaxies. Based on this catalog, we find that “special” galaxies (e.g., merging galaxies, barred galaxies, and active galactic nucleus host galaxies) contain more galaxies with highly asymmetric velocity maps. However, we notice that more than half of galaxies with high kinematic asymmetry in our sample are quite “regular.” For those “regular” galaxies, kinematic asymmetry shows a significant anticorrelation with stellar mass at <jats:inline-formula> <jats:tex-math> <?CDATA $\mathrm{log}{M}_{\star }\lt 9.7$?> </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:mo>⋆</mml:mo> </mml:mrow> </mml:msub> <mml:mo>&lt;</mml:mo> <mml:mn>9.7</mml:mn> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjsac80f2ieqn1.gif" xlink:type="simple" /> </jats:inline-formula>, while such a trend becomes very weak at <jats:inline-formula> <jats:tex-math> <?CDATA $\mathrm{log}{M}_{\star }\gt 9.7$?> </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:mo>⋆</mml:mo> </mml:mrow> </mml:msub> <mml:mo>&gt;</mml:mo> <mml:mn>9.7</mml:mn> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjsac80f2ieqn2.gif" xlink:type="simple" /> </jats:inline-formula>. Moreover, at a given stellar mass, the kinematic asymmetry shows weak correlations with photometric morphology, star formation rate, and environment, while it is independent of H <jats:sc>i</jats:sc> gas content. We also have quantified the observational effects in the kinematic asymmetry measurement. We find that both the signal-to-noise ratio of H<jats:italic>α</jats:italic> flux and disk inclination angle contribute to the measures of kinematic asymmetry, while the physical spatial resolution is an irrelevant factor inside the MaNGA redshift coverage.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Although previous searches for star clusters have been very successful, many clusters are likely still omitted, especially at high-Galactic-latitude regions. In this work, based on the astrometry of Gaia EDR3, we searched nearby (<jats:italic>ϖ</jats:italic> &gt; 0.8 mas) all-sky regions, obtaining 886 star clusters, of which 270 candidates have not been cataloged before. At the same time, we have presented the physical parameters of the clusters by fitting theoretical isochrones to their optical magnitudes. More halo members and expanding structures in many star clusters were also found. Most of the new objects are young clusters that are less than 100 million years old. Our work greatly increased the sample size and physical parameters of star clusters in the solar neighborhood, in particular, 46 clusters are newly found with ∣<jats:italic>b</jats:italic>∣ &gt; 20°, which represents a nearly threefold increase in the number of clusters at high-Galactic-latitude regions.</jats:p>