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Título de Acceso Abierto
The Astrophysical Journal Supplement (ApJS)
Resumen/Descripción – provisto por la editorial en inglés
The Astrophysical Journal Supplement is an open access journal publishing significant articles containing extensive data or calculations. ApJS also supports Special Issues, collections of thematically related papers published simultaneously in a single volume.Palabras clave – provistas por la editorial
astronomy; astrophysics
Disponibilidad
Institución detectada | Período | Navegá | Descargá | Solicitá |
---|---|---|---|---|
No detectada | desde dic. 1996 / hasta dic. 2023 | IOPScience |
Información
Tipo de recurso:
revistas
ISSN impreso
0067-0049
ISSN electrónico
1538-4365
Editor responsable
American Astronomical Society (AAS)
Idiomas de la publicación
- inglés
País de edición
Reino Unido
Información sobre licencias CC
Cobertura temática
Tabla de contenidos
The GBT Diffuse Ionized Gas Survey (GDIGS): Survey Overview and First Data Release
L. D. Anderson; Matteo Luisi; Bin Liu; Trey V. Wenger; Dana. S. Balser; T. M. Bania; L. M. Haffner; Dylan J. Linville; J. L. Mascoop
<jats:title>Abstract</jats:title> <jats:p>The Green Bank Telescope (GBT) Diffuse Ionized Gas Survey (GDIGS) traces ionized gas in the Galactic midplane by measuring 4–8 GHz radio recombination line (RRL) emission. The nominal survey zone is 32.°3 > <jats:italic>ℓ</jats:italic> > − 5°, ∣<jats:italic>b</jats:italic>∣ < 0.°5, but coverage extends above and below the plane in select fields and additionally includes the areas around W47 (<jats:italic>ℓ</jats:italic> ≃ 37.°5) and W49 (<jats:italic>ℓ</jats:italic> ≃ 43°). GDIGS simultaneously observes 22 Hn<jats:italic>α</jats:italic> (15 usable), 25 Hn<jats:italic>β</jats:italic> (18 usable), and 8 Hn<jats:italic>γ</jats:italic> RRLs (all usable), as well as multiple molecular line transitions (including those of <jats:inline-formula> <jats:tex-math> <?CDATA ${{\rm{H}}}_{2}^{13}\mathrm{CO}$?> </jats:tex-math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjsabef65ieqn1.gif" xlink:type="simple" /> </jats:inline-formula>, H<jats:sub>2</jats:sub>CO, and CH<jats:sub>3</jats:sub>OH). Here, we describe the GDIGS survey parameters and characterize the RRL data, focusing primarily on the Hn<jats:italic>α</jats:italic> data. We produce sensitive data cubes by averaging the usable RRLs, after first smoothing to a common spectral resolution of 0.5 km s<jats:sup>−1</jats:sup> and a spatial resolution of 2.′65 for Hn<jats:italic>α</jats:italic>, 2.′62 for Hn<jats:italic>β</jats:italic>, and 2.′09 for Hn<jats:italic>γ</jats:italic>. The average spectral noise per spaxel in the Hn<jats:italic>α</jats:italic> data cubes is ∼10 mK (∼5 mJy beam<jats:sup>−1</jats:sup>). This sensitivity allows GDIGS to detect RRLs from plasma throughout the inner Galaxy. The GDIGS Hn<jats:italic>α</jats:italic> data are sensitive to emission measures EM ≳ 1100 cm<jats:sup>−6</jats:sup> pc, which corresponds to a mean electron density 〈<jats:italic>n</jats:italic> <jats:sub> <jats:italic>e</jats:italic> </jats:sub>〉 ≳ 30 cm<jats:sup>−3</jats:sup> for a 1 pc path length or 〈<jats:italic>n</jats:italic> <jats:sub> <jats:italic>e</jats:italic> </jats:sub>〉 ≳ 1 cm<jats:sup>−3</jats:sup> for a 1 kpc path length.</jats:p>
Palabras clave: Space and Planetary Science; Astronomy and Astrophysics.
Pp. 28
A New Fast Monte Carlo Code for Solving Radiative Transfer Equations Based on the Neumann Solution
Yang Xiao-lin; Wang Jian-cheng; Yang Chu-yuan; Yuan Zun-li
<jats:title>Abstract</jats:title> <jats:p>In this paper, we propose a new Monte Carlo radiative transport (MCRT) scheme, which is based completely on the Neumann series solution of the Fredholm integral equation. This scheme indicates that the essence of MCRT is the calculation of infinite terms of multiple integrals in the Neumann solution simultaneously. Under this perspective, we redescribe the MCRT procedure systematically, in which the main work amounts to choosing an associated probability distribution function for a set of random variables and the corresponding unbiased estimation functions. We select a relatively optimal estimation procedure that has a lower variance from an infinite number of possible choices, such as term-by-term estimation. In this scheme, MCRT can be regarded as a pure problem of integral evaluation, rather than as the tracing of random-walking photons. Keeping this in mind, one can avert some subtle intuitive mistakes. In addition, the <jats:italic>δ</jats:italic> functions in these integrals can be eliminated in advance by integrating them out directly. This fact, together with the optimal chosen random variables, can remarkably improve the Monte Carlo (MC) computational efficiency and accuracy, especially in systems with axial or spherical symmetry. An MCRT code, Lemon (Linear integral Equations’ Monte carlo solver based On the Neumann solution; the code is available on the GitHub codebase at <jats:ext-link xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="uri" xlink:href="https://github.com/yangxiaolinyn/Lemon" xlink:type="simple">https://github.com/yangxiaolinyn/Lemon</jats:ext-link>, and version 2.0 is archived on Zenodo at <jats:ext-link xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="uri" xlink:href="https://doi.org/10.5281/zenodo.4686355" xlink:type="simple">https://doi.org/10.5281/zenodo.4686355</jats:ext-link>), has been developed completely based on this scheme. Finally, we intend to verify the validation of Lemon; a suite of test problems mainly restricted to a flat spacetime has been reproduced, and the corresponding results are illustrated in detail.</jats:p>
Palabras clave: Space and Planetary Science; Astronomy and Astrophysics.
Pp. 29
Catalog of One-side Head–Tail Galaxies in the FIRST Survey
Tong Pan; Heng Yu; Reinout J. van Weeren; Shumei Jia; Chengkui Li; Yipeng Lyu
<jats:title>Abstract</jats:title> <jats:p>One-side head–tail (OHT) galaxies are radio galaxies with a peculiar shape. They usually appear in galaxy clusters, but they have never been cataloged systematically. We design an automatic procedure to search for them in the Faint Images of the Radio Sky at Twenty-Centimeters source catalog and compile a sample with 115 HT candidates. After cross-checking with the Sloan Digital Sky Survey photometric data and catalogs of galaxy clusters, we find that 69 of them are possible OHT galaxies. Most of them are close to the center of galaxy clusters. The lengths of their tails do not correlate with the projection distance to the center of the nearest galaxy clusters, but show weak anticorrelation with the cluster richness, and are inversely proportional to the radial velocity differences between clusters and host galaxies. Our catalog provides a unique sample to study this special type of radio galaxies.</jats:p>
Palabras clave: Space and Planetary Science; Astronomy and Astrophysics.
Pp. 30
Stellar Metallicities from SkyMapper Photometry. II. Precise Photometric Metallicities of ∼280,000 Giant Stars with [Fe/H] < −0.75 in the Milky Way
Anirudh Chiti; Anna Frebel; Mohammad K. Mardini; Tatsuya W. Daniel; Xiaowei Ou; Anastasiia V. Uvarova
<jats:title>Abstract</jats:title> <jats:p>The Milky Way’s metal-poor stars are nearby ancient objects that are used to study early chemical evolution and the assembly and structure of the Milky Way. Here we present reliable metallicities of ∼280,000 stars with −3.75 ≲ [Fe/H] ≲ −0.75 down to <jats:italic>g</jats:italic> = 17 derived using metallicity-sensitive photometry from the second data release of the SkyMapper Southern Survey. We use the dependency of the flux through the SkyMapper <jats:italic>v</jats:italic> filter on the strength of the Ca <jats:sc>ii</jats:sc> K absorption features, in tandem with SkyMapper <jats:italic>u</jats:italic>, <jats:italic>g</jats:italic>, <jats:italic>i</jats:italic> photometry, to derive photometric metallicities for these stars. We find that metallicities derived in this way compare well to metallicities derived in large-scale spectroscopic surveys, and we use such comparisons to calibrate and quantify systematics as a function of location, reddening, and color. We find good agreement with metallicities from the APOGEE, LAMOST, and GALAH surveys, based on a standard deviation of <jats:italic>σ</jats:italic> ∼ 0.25 dex of the residuals of our photometric metallicities with respect to metallicities from those surveys. We also compare our derived photometric metallicities to metallicities presented in a number of high-resolution spectroscopic studies to validate the low-metallicity end ([Fe/H] < −2.5) of our photometric metallicity determinations. In such comparisons, we find the metallicities of stars with photometric [Fe/H] < −2.5 in our catalog show no significant offset and a scatter of <jats:italic>σ</jats:italic> ∼ 0.31 dex level relative to those in high-resolution work when considering the cooler stars (<jats:italic>g</jats:italic> − <jats:italic>i</jats:italic> > 0.65) in our sample. We also present an expanded catalog containing photometric metallicities of ∼720,000 stars as a data table for further exploration of the metal-poor Milky Way.</jats:p>
Palabras clave: Space and Planetary Science; Astronomy and Astrophysics.
Pp. 31
Strength of the Termination Shock Inferred from the Globally Distributed Energetic Neutral Atom Flux from IBEX
Bishwas L. Shrestha; Eric J. Zirnstein; Jacob Heerikhuisen; Gary P. Zank
<jats:title>Abstract</jats:title> <jats:p>In this study, we estimate the heliospheric termination shock (HTS) compression ratio at multiple directions in the sky from a quantitative comparison of the observed and simulated inner heliosheath (IHS) energetic neutral atom (ENA) fluxes. We use a 3D steady-state simulation of the heliosphere to simulate the ENA fluxes by postprocessing the MHD plasma using a multi-Maxwellian distribution for protons in the IHS. The simulated ENA fluxes are compared with time exposure–averaged IBEX-Hi data for the first 3 yr of the mission. The quantitative comparison is performed by calculating the fractional difference in the spectral slope between the observed and simulated ENA fluxes for a range of compression ratios, where the simulated ENA spectrum is varied as a function of downstream pickup ion temperature as a function of compression ratio. The estimated compression ratio in a particular direction is determined by the minimum value of the fractional difference in spectral slope. Our study shows that the compression ratio estimated by this method is in close agreement with the large-scale compression ratio observed by Voyager 2 in its travel direction. Also, the compression ratio in other directions near the ecliptic plane is similar to the compression ratio at the Voyager 2 direction. The weakest shock compression is found to be on the port side of the heliosphere at direction (27°, 15°). This is the first study to estimate the HTS compression ratio at multiple directions in the sky from IBEX data.</jats:p>
Palabras clave: Space and Planetary Science; Astronomy and Astrophysics.
Pp. 32
SPICY: The Spitzer/IRAC Candidate YSO Catalog for the Inner Galactic Midplane
Michael A. Kuhn; Rafael S. de Souza; Alberto Krone-Martins; Alfred Castro-Ginard; Emille E. O. Ishida; Matthew S. Povich; Lynne A. Hillenbrand
<jats:title>Abstract</jats:title> <jats:p>We present ∼120,000 Spitzer/IRAC candidate young stellar objects (YSOs) based on surveys of the Galactic midplane between <jats:italic>ℓ</jats:italic> ∼ 255° and 110°, including the GLIMPSE I, II, and 3D, Vela-Carina, Cygnus X, and SMOG surveys (613 square degrees), augmented by near-infrared catalogs. We employed a classification scheme that uses the flexibility of a tailored statistical learning method and curated YSO data sets to take full advantage of Spitzer’s spatial resolution and sensitivity in the mid-infrared ∼3–9 <jats:italic>μ</jats:italic>m range. Multiwavelength color/magnitude distributions provide intuition about how the classifier separates YSOs from other red IRAC sources and validate that the sample is consistent with expectations for disk/envelope-bearing pre–main-sequence stars. We also identify areas of IRAC color space associated with objects with strong silicate absorption or polycyclic aromatic hydrocarbon emission. Spatial distributions and variability properties help corroborate the youthful nature of our sample. Most of the candidates are in regions with mid-IR nebulosity, associated with star-forming clouds, but others appear distributed in the field. Using Gaia DR2 distance estimates, we find groups of YSO candidates associated with the Local Arm, the Sagittarius–Carina Arm, and the Scutum–Centaurus Arm. Candidate YSOs visible to the Zwicky Transient Facility tend to exhibit higher variability amplitudes than randomly selected field stars of the same magnitude, with many high-amplitude variables having light-curve morphologies characteristic of YSOs. Given that no current or planned instruments will significantly exceed IRAC’s spatial resolution while possessing its wide-area mapping capabilities, Spitzer-based catalogs such as ours will remain the main resources for mid-infrared YSOs in the Galactic midplane for the near future.</jats:p>
Palabras clave: Space and Planetary Science; Astronomy and Astrophysics.
Pp. 33
EXOPLINES: Molecular Absorption Cross-section Database for Brown Dwarf and Giant Exoplanet Atmospheres
Ehsan Gharib-Nezhad; Aishwarya R. Iyer; Michael R. Line; Richard S. Freedman; Mark S. Marley; Natasha E. Batalha
<jats:title>Abstract</jats:title> <jats:p>Stellar, substellar, and planetary atmosphere models are all highly sensitive to the input opacities. Generational differences between various state-of-the-art stellar/planetary models arise primarily because of incomplete and outdated atomic/molecular line lists. Here we present a database of precomputed absorption cross sections for all isotopologues of key atmospheric molecules relevant to late-type stellar, brown dwarf, and planetary atmospheres: MgH, AlH, CaH, TiH, CrH, FeH, SiO, TiO, VO, and H<jats:sub>2</jats:sub>O. The pressure and temperature ranges of the computed opacities are 10<jats:sup>−6</jats:sup>–3000 bar and 75–4000 K, and their spectral ranges are 0.25–330 <jats:italic>μ</jats:italic>m for many cases where possible. For cases with no pressure-broadening data, we use collision theory to bridge the gap. We also probe the effect of absorption cross sections calculated from different line lists in the context of ultrahot Jupiter and M-dwarf atmospheres. Using 1D self-consistent radiative–convective thermochemical equilibrium models, we report significant variations in the theoretical spectra and thermal profiles of substellar atmospheres. With a 2000 K representative ultrahot Jupiter, we report variations of up to 320 and 80 ppm in transmission and thermal emission spectra, respectively. For a 3000 K M-dwarf, we find differences of up to 125% in the spectra. We find that the most significant differences arise as a result of the choice of TiO line lists, primarily below 1 <jats:italic>μ</jats:italic>m. In summary, (1) we present a database of precomputed molecular absorption cross sections, and (2) we quantify biases that arise when characterizing substellar/exoplanet atmospheres as a result of differences in the line lists, therefore highlighting the importance of correct and complete opacities for eventual applications to high-precision spectroscopy and photometry.</jats:p>
Palabras clave: Space and Planetary Science; Astronomy and Astrophysics.
Pp. 34
Bayesian Time-resolved Spectroscopy of Multipulse GRBs: Variations of Emission Properties among Pulses
Liang Li; Felix Ryde; Asaf Pe’er; Hoi-Fung Yu; Zeynep Acuner
<jats:title>Abstract</jats:title> <jats:p>Gamma-ray bursts (GRBs) are highly variable and exhibit strong spectral evolution. In particular, the emission properties vary from pulse to pulse in multipulse bursts. Here we present a time-resolved Bayesian spectral analysis of a compilation of GRB pulses observed by the Fermi/Gamma-ray Burst Monitor. The pulses are selected to have at least four time bins with a high statistical significance, which ensures that the spectral fits are well determined and spectral correlations can be established. The sample consists of 39 bursts, 117 pulses, and 1228 spectra. We confirm the general trend that pulses become softer over time, with mainly the low-energy power-law index <jats:italic>α</jats:italic> becoming smaller. A few exceptions to this trend exist, with the hardest pulse occurring at late times. The first pulse in a burst is clearly different from the later pulses; three-fourths of them violate the synchrotron line of death, while around half of them significantly prefer photospheric emission. These fractions decrease for subsequent pulses. We also find that in two-thirds of the pulses, the spectral parameters (<jats:italic>α</jats:italic> and peak energy) track the light-curve variations. This is a larger fraction compared to what is found in previous samples. In conclusion, emission compatible with the GRB photosphere is typically found close to the trigger time, while the chance of detecting synchrotron emission is greatest at late times. This allows for the coexistence of emission mechanisms at late times.</jats:p>
Palabras clave: Space and Planetary Science; Astronomy and Astrophysics.
Pp. 35
The Southern H II Region Discovery Survey. II. The Full Catalog
Trey V. Wenger; J. R. Dawson; John M. Dickey; C. H. Jordan; N. M. McClure–Griffiths; L. D. Anderson; W. P. Armentrout; Dana S. Balser; T. M. Bania
<jats:title>Abstract</jats:title> <jats:p>The Southern H <jats:sc>ii</jats:sc> Region Discovery Survey (SHRDS) is a 900 hr Australia Telescope Compact Array 4–10 GHz radio continuum and radio recombination line (RRL) survey of Galactic H <jats:sc>ii</jats:sc> regions and infrared-identified H <jats:sc>ii</jats:sc> region candidates in the southern sky. For this data release, we reprocess all previously published SHRDS data and include an additional ∼450 hr of observations. The search for new H <jats:sc>ii</jats:sc> regions is now complete over the range 259° < <jats:italic>ℓ</jats:italic> < 346°, ∣<jats:italic>b</jats:italic>∣ < 4° for H <jats:sc>ii</jats:sc> region candidates with predicted 6 GHz continuum peak brightnesses ≳30 mJy beam<jats:sup>−1</jats:sup>. We detect radio continuum emission toward 730 targets altogether including previously known nebulae and H <jats:sc>ii</jats:sc> region candidates. By averaging ∼18 RRL transitions, we detect RRL emission toward 206 previously known H <jats:sc>ii</jats:sc> regions and 436 H <jats:sc>ii</jats:sc> region candidates. Including the northern sky surveys, over the last decade the H <jats:sc>ii</jats:sc> Region Discovery Surveys have more than doubled the number of known Galactic H <jats:sc>ii</jats:sc> regions. The census of H <jats:sc>ii</jats:sc> regions in the Wide-field Infrared Survey Explorer (WISE) Catalog of Galactic H <jats:sc>ii</jats:sc> Regions is now complete for nebulae with 9 GHz continuum flux densities ≳250 mJy. We compare the RRL properties of the newly discovered SHRDS nebulae with those of all previously known H <jats:sc>ii</jats:sc> regions. The median RRL FWHM line width of the entire WISE Catalog H <jats:sc>ii</jats:sc> region population is 23.9 km s<jats:sup>−1 </jats:sup>and is consistent between Galactic quadrants. The observed Galactic longitude–velocity asymmetry in the population of H <jats:sc>ii</jats:sc> regions probably reflects underlying spiral structure in the Milky Way.</jats:p>
Palabras clave: Space and Planetary Science; Astronomy and Astrophysics.
Pp. 36