- ID:
- ivo://CDS.VizieR/J/MNRAS/400/299
- Title:
- Chandra deep protocluster survey
- Short Name:
- J/MNRAS/400/299
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present X-ray point-source catalogues for a deep ~400ks Chandra ACIS-I (Advanced CCD Imaging Spectrometer) exposure of the SSA22 field. The observations are centred on a z=3.09 protocluster, which is populated by Lyman break galaxies (LBGs), Ly{alpha} emitters (LAEs) and extended Ly{alpha}-emitting blobs (LABs). The survey reaches ultimate (3 count) sensitivity limits of ~5.7x10^-17^ and ~3.0x10^-16^erg/cm^2^/s for the 0.5-2 and 2-8keV bands, respectively (corresponding to L_2-10keV_~5.7x10^42^erg/s and L_10-30keV_~2.0x10^43^erg/s at z=3.09, respectively, for an assumed photon index of {GAMMA}=1.4). These limits make SSA22 the fourth deepest extragalactic Chandra survey yet conducted, and the only one focused on a known high-redshift structure. In total, we detect 297 X-ray point sources and identify one obvious bright extended X-ray source over a ~330arcmin^2^ region. In addition to our X-ray catalogues, we provide all available optical spectroscopic redshifts and near-infrared and mid-infrared photometry available for our sources.
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Search Results
- ID:
- ivo://CDS.VizieR/J/MNRAS/458/4530
- Title:
- Chandra Galactic Bulge Survey
- Short Name:
- J/MNRAS/458/4530
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- As part of the Chandra Galactic Bulge Survey (GBS), we present a catalogue of optical sources in the GBS footprint. This consists of two regions centered at Galactic latitude b=1.5{deg} above and below the Galactic Centre, spanning (lxb)=(6{deg}x1{deg}). The catalogue consists of 2 or more epochs of observations for each line of sight in r', i' and H{alpha} filters. The catalogue is complete down to r'=20.2 and i'=19.2mag; the mean 5{sigma} depth is r'=22.5 and i'=21.1mag. The mean root-mean-square residuals of the astrometric solutions is 0.04-arcsec. We cross-correlate this optical catalogue with the 1640 unique X-ray sources detected in Chandra observations of the GBS area, and nd candidate optical counterparts to 1480 X-ray sources. We use a false alarm probability analysis to estimate the contamination by interlopers, and expect ~10 0 per cent of optical counterparts to be chance alignments. To determine the most likely counterpart for each X-ray source, we compute the likelihood ratio for all optical sources within the 4{sigma} X-ray error circle. This analysis yields 1480 potential counterparts (~90 per cent of the sample). 584 counterparts have saturated photometry (r'<=17, i'<=16), indicating these objects are likely foreground sources and the real counterparts. 171 candidate counterparts are detected only in the i' -band. These sources are good qLMXB and CV candidates as they are X-ray bright and likely located in the Bulge.
- ID:
- ivo://CDS.VizieR/J/ApJ/763/128
- Title:
- Chandra Local Volume Survey: NGC 404 sources
- Short Name:
- J/ApJ/763/128
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a comprehensive X-ray point-source catalog of NGC 404 obtained as part of the Chandra Local Volume Survey. A new 97ks Chandra ACIS-S observation of NGC 404 was combined with archival observations for a total exposure of ~123ks. Our survey yields 74 highly significant X-ray point sources and is sensitive to a limiting unabsorbed luminosity of ~6x10^35^erg/s in the 0.35-8keV band. To constrain the nature of each X-ray source, cross-correlations with multi-wavelength data were generated. We searched overlapping Hubble Space Telescope observations for optical counterparts to our X-ray detections, but find only two X-ray sources with candidate optical counterparts. We find 21 likely low-mass X-ray binaries (LMXBs), although this number is a lower limit due to the difficulties in separating LMXBs from background active galactic nuclei. The X-ray luminosity functions (XLFs) in both the soft and hard energy bands are presented. The XLFs in the soft band (0.5-2keV) and the hard band (2-8keV) have a limiting luminosity at the 90% completeness limit of 10^35^erg/s and 10^36^erg/s, respectively, significantly lower than previous X-ray studies of NGC 404. We find the XLFs to be consistent with those of other X-ray populations dominated by LMXBs. However, the number of luminous (>10^37^erg/s) X-ray sources per unit stellar mass in NGC 404 is lower than is observed for other galaxies. The relative lack of luminous XRBs may be due to a population of LMXBs with main-sequence companions formed during an epoch of elevated star formation ~0.5Gyr ago.
- ID:
- ivo://CDS.VizieR/J/ApJ/644/829
- Title:
- Chandra normal galaxies at intermediate redshift
- Short Name:
- J/ApJ/644/829
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have investigated 136 Chandra extragalactic sources, including 93 galaxies with narrow emission lines (NELGs) and 43 with only absorption lines (ALGs). Based on fX/fO, LX, X-ray spectral hardness, and optical emission-line diagnostics, we have conservatively classified 36 normal galaxies and 71 AGNs. Their redshift ranges from 0.01 to 1.2, with normal galaxies in the range z=0.01-0.3. Our normal galaxies appear to share characteristics with local galaxies, as expected from the X-ray binary populations and the hot interstellar matter (ISM). In conjunction with normal galaxies found in other surveys, we found no statistically significant evolution in LX/LB, within the limited z range (<~0.1).
- ID:
- ivo://CDS.VizieR/J/ApJ/774/23
- Title:
- Chandra observations of SPT-SZ clusters
- Short Name:
- J/ApJ/774/23
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present first results on the cooling properties derived from Chandra X-ray observations of 83 high-redshift (0.3<z<1.2) massive galaxy clusters selected by their Sunyaev-Zel'dovich signature in the South Pole Telescope data. We measure each cluster's central cooling time, central entropy, and mass deposition rate, and compare these properties to those for local cluster samples. We find no significant evolution from z~0 to z~1 in the distribution of these properties, suggesting that cooling in cluster cores is stable over long periods of time. We also find that the average cool core entropy profile in the inner ~100kpc has not changed dramatically since z~1, implying that feedback must be providing nearly constant energy injection to maintain the observed "entropy floor" at ~10keV cm^2^.
- ID:
- ivo://CDS.VizieR/J/ApJ/900/79
- Title:
- Chandra obs. of SDSS AGN pairs at z_med_~0.1
- Short Name:
- J/ApJ/900/79
- Date:
- 21 Mar 2022 09:29:38
- Publisher:
- CDS
- Description:
- We present a Chandra archival study of optically selected active galactic nucleus (AGN) pairs at a median redshift z~0.1. Out of 1286 AGN pairs (with projected separations rp<100kpc and velocity offsets {Delta}v<600km/s) optically identified from the Sloan Digital Sky Survey Seventh Data Release, we find 67 systems with archival Chandra observations, which represents the largest sample of optically selected AGN pairs studied in the X-ray. Among the 67 AGN pairs, 21 systems have both nuclei detected in the X-ray, 36 have one nucleus detected in the X-ray, and 10 have no X-ray detection. The X-ray detection rate, 78/134=58% (+/-7% 1{sigma} Poisson errors), is significantly higher than that (23/134=17%+/-4%) of a comparison sample of star-forming galaxy pairs, lending support to the optical AGN classification. In the conservative case where X-ray contamination from star formation is removed, the X-ray detection rate becomes 27%+/-4%, consistent with predictions from the latest galaxy merger simulations. The 2-10keV X-ray luminosity L2-10keV increases with decreasing projected separation in AGN pairs for rp>~15kpc, suggesting an enhancement of black hole accretion even in early-stage mergers. On the other hand, L2-10keV appears to decrease with decreasing projected separation at rp<~15kpc, which is contradictory to predictions from merger simulations. The apparent decrease in L2-10 keV of AGN pairs at rp<~15kpc may be caused by (i) enhanced absorbing columns from merger-induced gas inflows, (ii) feedback effects from early-stage mergers, and/or (iii) small number statistics. Future X-ray studies with larger samples are needed to put our results on firmer statistical ground.
- ID:
- ivo://CDS.VizieR/J/MNRAS/342/802
- Title:
- Chandra survey of 13-h XMM/ROSAT survey
- Short Name:
- J/MNRAS/342/802
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the results of a Chandra ACIS-I survey of a high-latitude region at 13h +38{deg} which was earlier observed with ROSAT and which has recently been observed by XMM-Newton for 200ks. XMM-Newton will provide good-quality X-ray spectra for over 200 sources with fluxes around the knee of the logN/logS, which are responsible for the bulk of the X-ray background. The main aim of the Chandra observations is to provide arcsecond, or better, positions, and hence reliable identifications, for the XMM-Newton sources. The ACIS-I observations were arranged in a mosaic of four 30-ks pointings, covering almost all of the 15-arcmin radius XMM-Newton/ROSAT field. We detect 214 Chandra sources above a Cash likelihood statistic of 25, which approximates to 5{sigma} significance, to a limiting flux of ~1.3x10^-15^erg/cm^2^/s (0.5-7keV). Optical counterparts are derived from a Subaru SuprimeCam image reaching to R~27. The very large majority of the Chandra sources have an optical counterpart, with the distribution peaking at 23<R<24, although 14 have no counterpart to R=27. The fraction of X-ray sources with no identification brighter than R=27 is similar to that found in deeper Chandra surveys.
- ID:
- ivo://CDS.VizieR/J/AJ/141/129
- Title:
- Chandra Transmission Grating Data Catalog
- Short Name:
- J/AJ/141/129
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The Chandra Transmission Grating Data Archive and Catalog (TGCat) provides easy access to analysis-ready products, specifically, high-resolution X-ray count spectra and their corresponding calibrations. The web interface makes it easy to find observations of a particular object, type of object, or type of observation; to quickly assess the quality and potential usefulness of the spectra from pre-computed summary plots; or to customize a view with an interactive plotter, optionally combining spectra over multiple orders or observations. Data and responses can be downloaded as a package or as individual files, and the query results themselves can be retrieved as ASCII or Virtual Observatory tables. Portable reprocessing scripts used to create the archive and which use the Chandra X-ray Center's (CXC's) software and other publicly available software are also available, facilitating standard or customized reprocessing from Level 1 CXC archival data to spectra and responses with minimal user interaction.
- ID:
- ivo://CDS.VizieR/J/ApJS/188/473
- Title:
- Chandra variable guide star catalog
- Short Name:
- J/ApJS/188/473
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Variable stars have been identified among the optical-wavelength light curves of guide stars used for pointing control of the Chandra X-ray Observatory. We present a catalog of these variable stars along with their light curves and ancillary data. Variability was detected to a lower limit of 0.02mag amplitude in the 4000-10000{AA} range using the photometrically stable Aspect Camera on board the Chandra spacecraft. The Chandra Variable Guide Star Catalog (VGUIDE) contains 827 stars, of which 586 are classified as definitely variable and 241 are identified as possibly variable. Of the 586 definite variable stars, we believe 319 are new variable star identifications. Types of variables in the catalog include eclipsing binaries, pulsating stars, and rotating stars. The variability was detected during the course of normal verification of each Chandra pointing and results from analysis of over 75000 guide star light curves from the Chandra mission. The VGUIDE catalog represents data from only about 9 years of the Chandra mission. Also, guide stars were often used multiple times for Chandra observations, so many of the stars in the VGUIDE catalog have multiple light curves available from various times in the mission. The catalog is presented as both online data associated with this paper and as a public Web interface. The stars available for use as Chandra guide stars are generally 6-11mag and are commonly spectral types A and later. Statistics of variability compared to spectral type indicate the expected dominance of A-F stars as pulsators. Eclipsing binaries are consistently 20%-30% of the detected variables across all spectral types.
- ID:
- ivo://CDS.VizieR/J/A+A/655/A109
- Title:
- Chandra view of the LX-LUV relation in quasars
- Short Name:
- J/A+A/655/A109
- Date:
- 22 Feb 2022
- Publisher:
- CDS
- Description:
- We present a study of the relation between X-rays and ultraviolet emission in quasars for a sample of broad-line, radio-quiet objects obtained from the cross-match of the Sloan Digital Sky Survey DR14 with the latest Chandra Source Catalog 2.0 (2332 quasars) and the Chandra COSMOS Legacy survey (273 quasars). The non-linear relation between the ultraviolet (at 2500{AA}, LUV) and the X-ray (at 2keV, LX) emission in quasars has been proved to be characterised by a smaller intrinsic dispersion than the observed one, as long as a homogeneous selection, aimed at preventing the inclusion of contaminants in the sample, is fulfilled. By leveraging on the low background of Chandra, we performed a complete spectral analysis of all the data available for the SDSS-CSC2.0 quasar sample (i.e. 3430 X-ray observations), with the main goal of reducing the uncertainties on the source properties (e.g. flux, spectral slope). We analysed whether any evolution of the LX-LUV relation exists by dividing the sample in narrow redshift intervals across the redshift range spanned by our sample, z~=0.5-4. We find that the slope of the relation does not evolve with redshift and it is consistent with the literature value of 0.6 over the explored redshift range, implying that the mechanism underlying the coupling of the accretion disc and hot corona is the same at the different cosmic epochs. We also find that the dispersion decreases when examining the highest redshifts, where only pointed observations are available. These results further confirm that quasars are 'standardisable candles', that is we can reliably measure cosmological distances at high redshifts where very few cosmological probes are available.
