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- ID:
- ivo://CDS.VizieR/J/ApJ/761/125
- Title:
- X and {gamma} spectral indexes of Fermi blazars
- Short Name:
- J/ApJ/761/125
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- In this paper, a sample of 451 blazars (193 flat spectrum radio quasars (FSRQs), 258 BL Lacertae objects) with corresponding X-ray and Fermi {gamma}-ray data is compiled to investigate the correlation both between the X-ray spectral index and the {gamma}-ray spectral index and between the spectral index and the luminosity, and to compare the spectral indexes {alpha}_X_, {alpha}_{gamma}_, {alpha}_X{gamma}_, and {alpha}_{gamma}X{gamma}_ for different subclasses. We also investigated the correlation between the X-ray and the {gamma}-ray luminosity.
- ID:
- ivo://CDS.VizieR/J/A+A/608/A39
- Title:
- X-ATLAS X-ray sources photometric redshifts
- Short Name:
- J/A+A/608/A39
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present photometric redshifts for 1,031 X-ray sources in the X-ATLAS field using the machine-learning technique TPZ. X-ATLAS covers 7.1 deg2 observed with XMM-Newton within the Science Demonstration Phase (SDP) of the H-ATLAS field, making it one of the largest contiguous areas of the sky with both XMM-Newton and Herschel coverage. All of the sources have available SDSS photometry, while 810 additionally have mid-IR and/or near-IR photometry. A spectroscopic sample of 5,157 sources primarily in the XMM/XXL field, but also from several X-ray surveys and the SDSS DR13 redshift catalogue, was used to train the algorithm. Our analysis reveals that the algorithm performs best when the sources are split, based on their optical morphology, into point-like and extended sources. Optical photometry alone is not enough to estimate accurate photometric redshifts, but the results greatly improve when at least mid-IR photometry is added in the training process. In particular, our measurements show that the estimated photometric redshifts for the X-ray sources of the training sample have a normalized absolute median deviation, nmadh0.06, and a percentage of outliers, {eta}=10-14%, depending upon whether the sources are extended or point like. Our final catalogue contains photometric redshifts for 933 out of the 1,031 X-ray sources with a median redshift of 0.9.
24174. XBACs, the sample
- ID:
- ivo://CDS.VizieR/J/MNRAS/281/799
- Title:
- XBACs, the sample
- Short Name:
- J/MNRAS/281/799
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present an essentially complete, all-sky, X-ray flux-limited sample of 242 Abell clusters of galaxies (six of which are double) compiled from ROSAT All-Sky Survey data. Our sample is uncontaminated in the sense that systems featuring prominent X-ray point sources such as AGN or foreground stars have been removed. The sample is limited to high Galactic latitudes (|b|>=20{deg}), the nominal redshift range of the ACO catalogue of z<=0.2, and X-ray fluxes above 5.0x10^-12^erg/cm^2^/s in the 0.1-2.4keV band. Owing to the X-ray flux limit, our sample consists, at intermediate and high redshifts, exclusively of very X-ray-luminous clusters. Since the latter tend to be also optically rich, the sample is not affected by the optical selection effects and, in particular, not by the volume incompleteness known to be present in the Abell and ACO catalogues for richness class 0 and 1 clusters. Our sample is the largest X-ray flux-limited sample of galaxy clusters compiled to date and will allow investigations of unprecedented statistical quality into the properties and distribution of rich clusters in the local Universe.
- ID:
- ivo://CDS.VizieR/J/ApJ/900/L10
- Title:
- X-band data of the GOTHAM Large Project for TMC-1
- Short Name:
- J/ApJ/900/L10
- Date:
- 15 Feb 2022 11:45:23
- Publisher:
- CDS
- Description:
- We present an overview of the GBT Observations of TMC-1: Hunting Aromatic Molecules Large Program on the Green Bank Telescope. This and a related program were launched to explore the depth and breadth of aromatic chemistry in the interstellar medium at the earliest stages of star formation, following our earlier detection of benzonitrile (c-C6H5CN) in TMC-1. In this work, details of the observations, use of archival data, and data reduction strategies are provided. Using these observations, the interstellar detection of propargyl cyanide (HCCCH2CN) is described, as well as the accompanying laboratory spectroscopy. We discuss these results, and the survey project as a whole, in the context of investigating a previously unexplored reservoir of complex, gas-phase molecules in pre-stellar sources. A series of companion papers describe other new astronomical detections and analyses.
- ID:
- ivo://nasa.heasarc/xbootesoid
- Title:
- XBOOTES:NDWFSBootesFieldOptical&NearIRCounterparts
- Short Name:
- XBOOTESOID
- Date:
- 14 Feb 2025
- Publisher:
- NASA/GSFC HEASARC
- Description:
- The XBootes Survey is a 5 ks Chandra survey of the Bootes Field of the NOAO Deep Wide-Field Survey (NDWFS). This survey is unique in that it is the largest (9.3 square degrees) contiguous region imaged in X-ray with complementary deep optical and near-infrared (near-IR) observations. The authors present a catalog of the optical counterparts to the 3213 X-ray point sources detected in the XBootes survey. Using a Bayesian identification scheme, they successfully identified optical counterparts for 98% of the X-ray point sources. The optical colors suggest that the optically detected galaxies are a combination of z < 1 massive early-type galaxies and bluer star-forming galaxies whose optical AGN emission is faint or obscured, whereas the majority of the optically detected point sources are likely quasars over a large redshift range. This large-area, X-ray-bright, optically deep survey enables the authors to select a large subsample of sources (773) with high X-ray to optical flux ratios (f<sub>X</sub>/f<sub>o</sub> > 10). These objects are likely high-redshift and/or dust-obscured AGNs. These sources have generally harder X-ray spectra than sources with 0.1 < f<sub>X</sub>/f<sub>o</sub> < 10. Of the 73 X-ray sources with no optical counterpart in the NDWFS catalog, 47 are truly optically blank down to R ~ 25.5 (the average 50% completeness limit of the NDWFS R-band catalogs). These sources are also likely to be high-redshift and/or dust-obscured AGNs. The 9.3 square degrees region of sky chosen to match the area covered with the NDWFS was observed by ACIS-I on the Chandra X-Ray Observatory over a 2 week time interval in 2003 March and April. The data were taken in 126 separate pointings, each observed for ~ 5 ks. The CIAO 3.0.2 wavelet detection algorithm (wavdetect; Freeman et al. 2002) was used to detect X-ray sources in the total (0.5 - 7.0 keV) band data. A probability threshold of 5 x 10-5 was chosen as the best compromise between maximizing the completeness while minimizing the number of spurious detections. The X-ray catalog comprises 3293 unique X-ray sources with >= 4 counts in the total-band images (Paper II). The authors expect only ~ 35 of these sources to be spurious in the full survey (Paper II). For the matching with cataloged optical counterparts, the authors only considered the 3213 X-ray sources that overlap with the NDWFS area. The authors include all multiply matched sources with >1% probability of being the correct optical counterpart. This table contains the X-ray and optical characteristics of the matched optical/X-ray catalog for the Chandra sources in the XBootes and NDWFS survey, and is Version 1.0, dated 21st June 2005. This table was created in November 2006 by the HEASARC based on the file xbootes_cat_xray_opt_IR_21jun_v1.0.txt obtained from the NOAO ftp area <a href="https://www.noao.edu/noao/noaodeep/XBootesPublic/">https://www.noao.edu/noao/noaodeep/XBootesPublic/</a>. This is a service provided by NASA HEASARC .
- ID:
- ivo://nasa.heasarc/xbootes
- Title:
- XBOOTES: NDWFS Bootes Field X-Ray Point Source Catalog
- Short Name:
- XBootes
- Date:
- 14 Feb 2025
- Publisher:
- NASA/GSFC HEASARC
- Description:
- The XBootes table contains the X-Ray point source catalog from a Chandra survey of the 9 square degrees Bootes field of the NOAO Deep Wide-Field Survey (NDWFS). This XBootes survey consists of 126 separate contiguous ACIS-I observations each of approximately 5000 s in duration. These unique Chandra observations allowed the authors to search for large-scale structure and to calculate X-ray source statistics over a wide, contiguous field of view with arcsecond angular resolution and uniform coverage. Optical spectroscopic follow-up observations and the rich NDWFS data set will allow the authors to identify and classify these X-ray-selected sources. Using wavelet decomposition, they have detected 4642 point sources with n >= 2 counts. In order to keep their detections ~ 99% reliable, they have limited their list to sources with n >= 4 counts. For a 5000 s observation and assuming a canonical unabsorbed active galactic nucleus (AGN) type X-ray spectrum, a 4 count on-axis source corresponds to a flux of 4.7 x 10<sup>-15</sup> ergs cm<sup>-2</sup> s<sup>-1</sup> in the soft (0.5-2 keV) band, 1.5 x 10<sup>-14</sup> ergs cm<sup>-2</sup> s<sup>-1</sup> in the hard (2-7 keV) band, and 7.8 x 10<sup>-15</sup> ergs cm<sup>-2</sup> s<sup>-1</sup> in the full (0.5-7 keV) band. The full 0.5-7 keV band n >= 4 count list contained in this HEASARC table has 3293 point sources. In addition to the point sources, 43 extended sources (not included in this HEASARC table) have been detected, consistent with the depth of these observations and the number counts of clusters. Presented here in the X-ray point source catalog for the XBootes survey are the source positions, X-ray fluxes, hardness ratios, and their uncertainties, for the 3293 sources with >= 4 counts in the full band. This table was created by the HEASARC in February 2006 based on the machine-readable version of Table 3 in the above paper which was obtained from the electronic ApJ website. This is a service provided by NASA HEASARC .
- ID:
- ivo://CDS.VizieR/I/302
- Title:
- XC1 catalogue of positions and proper motions
- Short Name:
- I/302
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the astrometric catalogue of faint reference stars in 255deg^2^ sized fields with ICRF objects of northern hemisphere. The XC1 is based on our results of measurements and astrometric reduction of digitized images of Schmidt plates POSS-I and POSS-II sky surveys obtained from USNOFS PMM Image Archive. The Tycho-2 (Cat. <I/259>) catalogue was used as a reference catalogue for astrometric reductions. The mean positions and proper motions of stars were derived from their individual positions at the different epochs. For some stars the 2MASS (Cat. <II/246>) positions were used also. The limiting magnitude is about V=19mag. The estimated external errors are 50-150mas in positions at mean epoch, and 2-5mas/yr in proper motions, depending on magnitude. The catalog is present as a set of individual fields in separate files. The name of each file is the ERS designation of corresponding ICRF radio source.
24179. X-CLASS/GROND catalogue
- ID:
- ivo://CDS.VizieR/J/MNRAS/468/662
- Title:
- X-CLASS/GROND catalogue
- Short Name:
- J/MNRAS/468/662
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The XMM Cluster Archive Super Survey (X-CLASS) is a serendipitously detected X-ray-selected sample of 845 galaxy clusters based on 2774 XMM archival observations and covering an approximately 90deg^2^ spread across the high-Galactic latitude (|b|>20{deg}) sky. The primary goal of this survey is to produce a well-selected sample of galaxy clusters on which cosmological analyses can be performed. This paper presents the photometric redshift follow-up of a high signal-to-noise ratio subset of 265 of these clusters with declination {delta}<+20{deg} with Gamma-Ray Burst Optical and Near-Infrared Detector (GROND), a 7-channel (grizJHK) simultaneous imager on the MPG 2.2-m telescope at the ESO La Silla Observatory. We use a newly developed technique based on the red sequence colour-redshift relation, enhanced with information coming from the X-ray detection to provide photometric redshifts for this sample. We determine photometric redshifts for 232 clusters, finding a median redshift of z=0.39 with an accuracy of {Delta}z=0.02(1+z) when compared to a sample of 76 spectroscopically confirmed clusters. We also compute X-ray luminosities for the entire sample and find a median bolometric luminosity of 7.2x10^43^erg/s and a median temperature of 2.9 keV. We compare our results to those of the XMM-XCS and XMM-XXL surveys, finding good agreement in both samples. The X-CLASS catalogue is available online at http://xmm-lss.in2p3.fr:8080/l4sdb/.
- ID:
- ivo://CDS.VizieR/J/A+A/649/A39
- Title:
- xCOLD GASS and xGASS. Metallicity gradients
- Short Name:
- J/A+A/649/A39
- Date:
- 22 Feb 2022
- Publisher:
- CDS
- Description:
- The xGASS and xCOLD GASS surveys have measured the atomic (HI) and molecular gas (H_2_) content of a large and representative sample of nearby galaxies (redshift range of 0.01<z<0.05). We present optical longslit spectra for a subset of the xGASS and xCOLD GASS galaxies to investigate the correlation between radial metallicity profiles and cold gas content. In addition to data from Moran et al. (2012ApJ...745...66M), this paper presents new optical spectra for 27 galaxies in the stellar mass range of 9.0<=logMstar[Msun]<=10.0. The longslit spectra were taken along the major axis of the galaxies, allowing us to obtain radial profiles of the gas-phase oxygen abundance (12+log(O/H)). The slope of a linear fit to these radial profiles is defined as the metallicity gradient. We investigated correlations between these gradients and global galaxy properties, such as star formation activity and gas content. In addition, we examined the correlation of local metallicity measurements and the global HI mass fraction. We obtained two main results: (i) the local metallicity is correlated with the global HI mass fraction, which is in good agreement with previous results. A simple toy model suggests that this correlation points towards a 'local gas regulator model'; (ii) the primary driver of metallicity gradients appears to be stellar mass surface density (as a proxy for morphology). This work comprises one of the few systematic observational studies of the influence of the cold gas on the chemical evolution of star-forming galaxies, as considered via metallicity gradients and local measurements of the gas-phase oxygen abundance. Our results suggest that local density and local HI mass fraction are drivers of chemical evolution and the gas-phase metallicity.
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