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15371. The CGS. IX. R-band single-Sersic fits to ellipticals
ID:
ivo://CDS.VizieR/J/ApJS/247/20
Title:
The CGS. IX. R-band single-Sersic fits to ellipticals
Short Name:
J/ApJS/247/20
Date:
21 Oct 2021
Publisher:
CDS
Description:
We study the statistical properties of 320 bulges of disk galaxies in the Carnegie-Irvine Galaxy Survey, using robust structural parameters of galaxies derived from image fitting. We apply the Kormendy relation to classify classical and pseudo bulges and characterize the bulge dichotomy with respect to the structural properties of the bulges and the physical properties of the host galaxies. We confirm previous findings that pseudo bulges on average have smaller Sersic indices, lower bulge-to-total ratios, and fainter surface brightnesses than classical bulges. Our sizable sample statistically shows that pseudo bulges are more intrinsically flattened than classical bulges. Pseudo bulges are most frequent (incidence >~80%) in late-type spirals (later than Sc). Our measurements support the picture in which pseudo bulges arose from star formation induced by inflowing gas, while classical bulges were born out of violent processes such as mergers and coalescence of clumps. We reveal differences with the literature that warrant attention: (1) the bimodal distribution of Sersic indices presented by previous studies is not reproduced in our study; (2) classical and pseudo bulges have similar relative bulge sizes; and (3) the pseudo bulge fraction is considerably smaller in early-type disks than reported in previous studies based on one-dimensional surface brightness profile fitting. We attribute these differences to our improved image quality, more robust bulge-to-disk decomposition technique, and to the different classification criteria that we applied. Moreover, we find that barred galaxies do not host more pseudo bulges or more prominent pseudo bulges than unbarred galaxies. Various implications of these findings are discussed.
15372. The CGS. VIII. R-band images of disk galaxies
ID:
ivo://CDS.VizieR/J/ApJS/244/34
Title:
The CGS. VIII. R-band images of disk galaxies
Short Name:
J/ApJS/244/34
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present multicomponent decomposition of high-quality R-band images of 320 disk galaxies from the Carnegie-Irvine Galaxy Survey. In addition to bulges and disks, we successfully model nuclei, bars, disk breaks, nuclear/inner lenses, and inner rings. Our modeling strategy treats nuclear rings and nuclear bars as part of the bulge component, while other features such as spiral arms, outer lenses, and outer rings are omitted from the fits because they are not crucial for accurate bulge measurements. The error budget of bulge parameters includes the uncertainties from sky-level measurements and model assumptions. Comparison with multicomponent decomposition from the Spitzer Survey of Stellar Structure in Galaxies reveals broad agreement for the majority of the overlapping galaxies, but for a considerable fraction of galaxies there are significant differences in bulge parameters caused by different strategies in model construction. We confirm that on average bulge prominence decreases from early- to late-type disk galaxies, although the large scatter of bulge-to-total ratios in each morphological bin limits the application of Hubble type as an accurate predictor of bulge-to-total ratio. In contrast with previous studies claiming that barred galaxies host weaker bulges, we find that barred and unbarred spiral galaxies have similar bulge prominence.
15373. The Chandra Archive Log
ID:
ivo://CDS.VizieR/B/chandra
Title:
The Chandra Archive Log
Short Name:
B/chandra
Date:
07 Mar 2022 06:17:49
Publisher:
CDS
Description:
The Chandra X-Ray Observatory (CXO) is a high-resolution (< 0.5 arcsecond) X-ray telescope with a suite of advanced imaging and spectroscopic instruments. The Observatory was successfully launched by NASA's Space Shuttle Columbia on July 23, 1999. Chandra was designed to provide order-of-magnitude advances over previous X-ray astronomy missions with regards to spatial and spectral resolution. The High Resolution Mirror Assembly (HRMA) produces images with a half-power diameter (HPD) of the point spread function (PSF) of < 0.5 arcsec. Chandra has two focal plane science instruments, i) The Advanced CCD Imaging Spectrometer (ACIS), and ii) The High Resolution Camera (HRC). ACIS is comprised of two CCD arrays, a 4-chip array, ACIS-I ; and a 6-chip array, ACIS-S . ACIS-I was designed for CCD imaging and spectrometry; ACIS-S can be used both for CCD imaging spectrometry and also for high-resolution spectroscopy in conjunction with the HETG grating. A mix of ACIS-S and ACIS-I chips (up to six) may be used for imaging observations. The HRC is comprised of two microchannel plate (MCP ) imaging detectors: the HRC-I designed for wide-field imaging; and, HRC-S designed to serve as a readout for the LETG . The grating systems consist of the Low Energy Transmission Grating (LETG) and the High Energy Transmission Grating (HETG). The HETG , when operated with the HRMA and the ACIS-S , forms the High-Energy Transmission Grating Spectrometer (HETGS ) for high resolution spectroscopy . The HETGS achieves resolving power up to 1000 in the band between 0.4 keV and 10.0 keV. The LETG when operated with the HRC-S , forms the Low Energy Transmission Grating Spectrometer (LETGS ). The LETGS provides the highest spectral resolution on Chandra at low (0.08 - 0.2 keV) energies. This catalogue is a copy of the Chandra Observation Catalog from the Chandra Data Archive (CDA) which is part of the Chandra X-Ray Observatory Science Center (CXC) which is operated for NASA by the Smithsonian Astrophysical Observatory.
15374. The Chandra COSMOS survey. III.
ID:
ivo://CDS.VizieR/J/ApJS/201/30
Title:
The Chandra COSMOS survey. III.
Short Name:
J/ApJS/201/30
Date:
21 Oct 2021
Publisher:
CDS
Description:
The Chandra COSMOS Survey (C-COSMOS) is a large, 1.8Ms, Chandra program that has imaged the central 0.9deg^2^ of the COSMOS field down to limiting depths of 1.9x10^-16^erg/cm^2^/s in the soft (0.5-2keV) band, 7.3x10^-16^erg/cm^2^/s in the hard (2-10keV) band, and 5.7x10^-16^erg/cm^2^/s in the full (0.5-10keV) band. In this paper we report the i, K, and 3.6um identifications of the 1761 X-ray point sources. We use the likelihood ratio technique to derive the association of optical/infrared counterparts for 97% of the X-ray sources. For most of the remaining 3%, the presence of multiple counterparts or the faintness of the possible counterpart prevented a unique association. For only 10 X-ray sources we were not able to associate a counterpart, mostly due to the presence of a very bright field source close by. Only two sources are truly empty fields. The full catalog, including spectroscopic and photometric redshifts and classification described here in detail, is available online.
15375. The Chandra Deep Fields North and South
ID:
ivo://CDS.VizieR/J/AJ/126/539
Title:
The Chandra Deep Fields North and South
Short Name:
J/AJ/126/539
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present point-source catalogs for the ~2Ms exposure of the Chandra Deep Field North, currently the deepest X-ray observation of the universe in the 0.5-8.0keV band. Five hundred and three (503) X-ray sources are detected over an ~448arcmin^2^ area in up to seven X-ray bands. Twenty (20) of these X-ray sources lie in the central 5.3 arcmin^2^ Hubble Deep Field North (13600^+3800^_-3000_sources/deg^2^). The on-axis sensitivity limits are 2.5x10^-17^ergs/cm^2^/s (0.5-2.0keV) and 1.4x10^-16^ergs/cm^2^/s (2-8keV). Source positions are determined using matched-filter and centroiding techniques; the median positional uncertainty is ~0.3". To allow consistent comparisons, the point-source catalogs for the 1Ms Chandra Deep Field South (CDF-S; see Cat. J/ApJS/139/369) have also been produced. Three hundred and twenty-six (326) X-ray sources are included in the main Chandra South catalog, and an additional 42 optically bright X-ray sources are included in a lower significance Chandra catalog. We find good agreement with the photometry of the previously published CDF-S catalogs; however, we provide significantly improved positional accuracy.
15376. The Chandra Source Catalog (CSC), Release 2.0
ID:
ivo://CDS.VizieR/IX/57
Title:
The Chandra Source Catalog (CSC), Release 2.0
Short Name:
IX/57
Date:
21 Oct 2021
Publisher:
CDS
Description:
The Chandra Source Catalog (CSC) is the definitive catalog of X-ray sources detected by the Chandra X-ray Observatory. By combining Chandra's sub-arcsecond on-axis spatial resolution and low instrumental background with consistent data processing, the CSC delivers a wide variety of uniformly calibrated properties and science ready data products for detected sources over four decades of flux. The second major release of the catalog, CSC 2.0, includes measured properties for 317,167 unique compact and extended X-ray sources in the sky, allowing statistical analysis of large samples, as well as individual source studies. The sensitivity limit for compact sources in CSC 2.0 is ~5 net counts (a factor of >~2 better than the previous catalog release). This improvement is achieved by using a two-stage approach that involves co-adding multiple observations of the same field prior to source detection, and then using an optimized source detection method.
15377. The Chandra Source Catalog, Release 1.1
ID:
ivo://CDS.VizieR/IX/45
Title:
The Chandra Source Catalog, Release 1.1
Short Name:
IX/45
Date:
21 Oct 2021
Publisher:
CDS
Description:
The Chandra Source Catalog (CSC) is a general purpose virtual X-ray astrophysics facility that provides access to a carefully selected set of generally useful quantities for individual X-ray sources, and is designed to satisfy the needs of a broad-based group of scientists, including those who may be less familiar with astronomical data analysis in the X-ray regime. The first release of the CSC includes information about 94,676 distinct X-ray sources detected in a subset of public Advanced CCD Imaging Spectrometer imaging observations from roughly the first eight years of the Chandra mission. This release of the catalog includes point and compact sources with observed spatial extents <~30''. The catalog (1) provides access to the best estimates of the X-ray source properties for detected sources, with good scientific fidelity, and directly supports scientific analysis using the individual source data; (2) facilitates analysis of a wide range of statistical properties for classes of X-ray sources; and (3) provides efficient access to calibrated observational data and ancillary data products for individual X-ray sources, so that users can perform detailed further analysis using existing tools. The catalog includes real X-ray sources detected with flux estimates that are at least 3 times their estimated 1-{sigma} uncertainties in at least one energy band, while maintaining the number of spurious sources at a level of <~1 false source per field for a 100ks observation. For each detected source, the CSC provides commonly tabulated quantities, including source position, extent, multi-band fluxes, hardness ratios, and variability statistics, derived from the observations in which the source is detected. In addition to these traditional catalog elements, for each X-ray source the CSC includes an extensive set of file-based data products that can be manipulated interactively, including source images, event lists, light curves, and spectra from each observation in which a source is detected.
15378. The Chandra survey of the SMC "Bar". II.
ID:
ivo://CDS.VizieR/J/ApJ/697/1695
Title:
The Chandra survey of the SMC "Bar". II.
Short Name:
J/ApJ/697/1695
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present the most likely optical counterparts of 113 X-ray sources detected in our Chandra survey of the central region of the Small Magellanic Cloud (SMC) based on the OGLE-II and Magellanic Clouds Photometric Survey catalogs. We estimate that the foreground contamination and chance coincidence probability are minimal for the bright optical counterparts (corresponding to OB type stars; 35 in total). We propose here for the first time 13 high-mass X-ray binaries, of which four are Be/X-ray binaries (Be-XRBs), and we confirm the previous classification of 18 Be-XRBs. We estimate that the new candidate Be-XRBs have an age of ~15-85Myr, consistent with the age of Be stars.
15379. The Chandra UDS survey (X-UDS)
ID:
ivo://CDS.VizieR/J/ApJS/236/48
Title:
The Chandra UDS survey (X-UDS)
Short Name:
J/ApJS/236/48
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present the X-UDS survey, a set of wide and deep Chandra observations of the Subaru-XMM Deep/UKIDSS Ultra Deep Survey (SXDS/UDS) field. The survey consists of 25 observations that cover a total area of 0.33deg^2^. The observations are combined to provide a nominal depth of ~600ks in the central 100arcmin^2^ region of the field that has been imaged with Hubble/WFC3 by the CANDELS survey and ~200ks in the remainder of the field. In this paper, we outline the survey's scientific goals, describe our observing strategy, and detail our data reduction and point source detection algorithms. Our analysis has resulted in a total of 868 band-merged point sources detected with a false-positive Poisson probability of <1x10^-4^. In addition, we present the results of an X-ray spectral analysis and provide best-fitting neutral hydrogen column densities, N_H_, as well as a sample of 51 Compton-thick active galactic nucleus candidates. Using this sample, we find the intrinsic Compton-thick fraction to be 30%-35% over a wide range in redshift (z=0.1-3), suggesting the obscured fraction does not evolve very strongly with epoch. However, if we assume that the Compton-thick fraction is dependent on luminosity, as is seen for Compton-thin sources, then our results are consistent with a rise in the obscured fraction out to z~3. Finally, an examination of the host morphologies of our Compton-thick candidates shows a high fraction of morphological disturbances, in agreement with our previous results.
15380. The CIDA Variability Survey of Orion OB1. II.
ID:
ivo://CDS.VizieR/J/AJ/157/85
Title:
The CIDA Variability Survey of Orion OB1. II.
Short Name:
J/AJ/157/85
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present results of our large-scale, optical, multi-epoch photometric survey across ~180 square degrees in the Orion OB1 association, complemented with extensive follow-up spectroscopy. Our focus is mapping and characterizing the off-cloud, low-mass, pre-main-sequence (PMS) populations. We report 2062 K- and M-type confirmed T Tauri members; 59% are located in the OB1a subassociation, 27% in the OB1b subassociation, and the remaining 14% in the A and B molecular clouds. We characterize two new clusterings of T Tauri stars, the HD 35762 and HR 1833 groups, both located in OB1a not far from the 25 Ori cluster. We also identify two stellar overdensities in OB1b, containing 231 PMS stars, and find that the OB1b region is composed of two populations at different distances, possibly due to the OB1a subassociation overlapping with the front of OB1b. A ~2 deg wide halo of young stars surrounds the Orion Nebula Cluster, corresponding in part to the low-mass populations of NGC 1977 and NGC 1980. We use the strength of H{alpha} in emission, combined with the IR excess and optical variability, to define a new type of T Tauri star, the C/W class, stars we propose may be nearing the end of their accretion phase, in an evolutionary state between classical and weak-lined T Tauri stars. The evolution of the ensemble-wide equivalent width of Li I{lambda}6707 indicates a Li depletion timescale of ~8.5 Myr. Disk accretion declines with an e-folding timescale of ~2 Myr, consistent with previous studies.

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