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ELAISCXO - ELAIS N1 and N2 Fields Chandra X-Ray Point Source Catalog

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Overview

This table contains the results of an analysis of two deep (75 ks) Chandra observations of the European Large Area Infrared Space Observatory (ISO) Survey (ELAIS) fields N1 and N2 as the first results from the ELAIS deep X-ray survey. This survey is being conducted in well-studied regions with extensive multiwavelength coverage. This table contains the Chandra source catalogs along with an analysis of source counts and hardness ratios. A total of 233 X-ray point sources were detected in addition to two soft extended sources (not included in this table of point sources), which are found to be associated with galaxy clusters. An overdensity of sources is found in N1 with 30 per cent more sources than N2, which the authors attribute to large-scale structure. A similar variance is seen between other deep Chandra surveys. The source count statistics reveal an increasing fraction of hard sources at fainter fluxes. The number of galaxy-like counterparts also increases dramatically towards fainter fluxes, consistent with the emergence of a large population of obscured sources.

The ELAIS Deep X-ray Survey (EDXS) is being conducted in the northern ELAIS regions N1 and N2. The Chandra data consist of approximately 75 ks exposures in each field. Region N1 was observed on 2000 August 3-4 (Obs_ID 888) and N2 on 2000 August 2-3 (Obs_ID 887). The nominal aimpoints were 16:10:20.11 +54:33:22.3 for N1, and 16:36:46.99 +41:01:33.7 for N2 in J2000.0 coordinates. The ACIS-I chips were used with the addition of the ACIS-S2 and ACIS-S4 chips.


Catalog Bibcode

2003MNRAS.343..293M

References

The ELAIS deep X-ray survey. I. Chandra source catalogue and first results.
    Manners J.C., Johnson O., Almaini O., Willott C.J., Gonzalez-Solares E.,
    Lawrence A., Mann R.G., Perez-Fournon I., Dunlop J.S., Mcmahon R.G.,
    Oliver S.J., Rowan-Robinson M., Serjeant S.
   <Mon. Not. R. Astron. Soc., 343, 293-305 (2003)>
   =2003MNRAS.343..293M

Provenance

This table was created by the HEASARC in February 2007 based on the CDS catalog J/MNRAS/343/293 files table1.dat and table2.dat.

Parameters

Source_Number
This X-ray source identifier consists of the field identifier (N1 or N2) and a running source number NNN in order of increasing J2000.0 Right Ascension within the field, viz., N1-NNN or N2-NNN.

Alt_Name
An alternative name for the X-ray source using the '[MJA2003]' prefix (for Manners, Johnson and Almaini 2003) and the source number value, as recommended by the CDS Dictionary of Nomenclature of Celestial Objects.

Name
The X-ray source designation using the 'CXOEN1' prefix for sources in the N1 field and 'CXOEN2' prefix for those in the N2 field and the truncated J2000.0 equatorial coordinates (JHHMMSS.s+DDMMSS), as registered with the CDS Dictionary of Nomenclature of Celestial Objects.

RA
The Right Ascension of the X-ray source in the selected equinox. This was given in J2000.0 coordinates to a precision of 0.01 seconds of time in the original tables. Source coordinates were astrometrically corrected using calibrated r'-band images to a depth of r' ~ 26. High S/N Chandra sources were matched with stellar r'-band counterparts (16 in N1 and 11 in N2, with a good spread across the fields). The rms residuals were all less than 1", randomly distributed with a mean of ~0.4".

Dec
The Declination of the X-ray source in the selected equinox. This was given in J2000.0 coordinates to a precision of 0.1 arcseconds in the original tables. Source coordinates were astrometrically corrected using calibrated r'-band images to a depth of r' ~ 26. High S/N Chandra sources were matched with stellar r'-band counterparts (16 in N1 and 11 in N2, with a good spread across the fields). The rms residuals were all less than 1", randomly distributed with a mean of ~0.4".

LII
The Galactic Longitude of the X-ray source.

BII
The Galactic Latitude of the X-ray source.

Error_Radius
The positional uncertainty of the X-ray source location, in arcseconds. This is the error in the centroid position from the source detection algorithm, with 0.4" added in quadrature to represent the astrometroc error.

Counts
The net counts C in the X-ray source, being the background-subtracted net source counts in the full energy band (0.5-8 keV). Where sources were only detected in the soft or hard bands, the net counts represent the counts in the corresponding band rather than in the full band.

SNR
The signal-to-noise ratio S/N of the X-ray source. A S/N threshold of 3 was used for source detection, where S/N is defined as C/(1+sqrt(0.75 +B)), where C are the net source counts, and B are the background counts within the source cell, the region defined by WAVDETECT which is assumed to effectively contain all the source counts. (This equation comes from Gehrels (1986, ApJ, 303, 336) equation 7 in which the upper confidence level equivalent to a 1-sigma Gaussian is given).

FB_Flux_Limit
This parameter is set to '<' if the quoted full-band (0.5 - 8 keV) flux is an upper limit.

FB_Flux
The full-band (0.5 - 8 keV) flux of the X-ray source, in erg/cm^2/s. Flux values were calculated assuming a power-law source spectrum of the form F(nu) ~ nu^-alpha, where alpha = 0.7. For sources that do not reach the S/N threshold in a certain band, an upper limit to the flux in that band was calculated using equation (5) in the reference paper. (For more details see Section 5 of the reference paper).

FB_Flux_Error
The RMS uncertainty in the full-band (0.5 - 8 keV) flux of the X-ray source, in erg/cm^2/s.

SB_Flux_Limit
This parameter is set to '<' if the quoted soft-band (0.5 - 2 keV) flux is an upper limit.

SB_Flux
The soft-band (0.5 - 2 keV) flux of the X-ray source, in erg/cm^2/s. Flux values were calculated assuming a power-law source spectrum of the form F(nu) ~ nu^-alpha, where alpha = 0.7. For sources that do not reach the S/N threshold in a certain band, an upper limit to the flux in that band was calculated using equation (5) in the reference paper. (For more details see Section 5 of the reference paper).

SB_Flux_Error
The RMS uncertainty in the soft-band (0.5 - 2 keV) flux of the X-ray source, in erg/cm^2/s.

HB_Flux_Limit
This parameter is set to '<' if the quoted hard-band (2 - 8 keV) flux is an upper limit.

HB_Flux
The hard-band (2 - 8 keV) flux of the X-ray source, in erg/cm^2/s. Flux values were calculated assuming a power-law source spectrum of the form F(nu) ~ nu^-alpha, where alpha = 0.7. For sources that do not reach the S/N threshold in a certain band, an upper limit to the flux in that band was calculated using equation (5) in the reference paper. (For more details see Section 5 of the reference paper).

HB_Flux_Error
The RMS uncertainty in the hard-band (2 - 8 keV) flux of the X-ray source, in erg/cm^2/s.

Hardness_Ratio
The broad-band hardness ratio HR of the X-ray source defined as HR = (H-S)/(H+S), where H and S are the background-subtracted source counts in the hard (2 - 8 keV) and soft (0.5 - 2 keV) bands, respectively. Net source counts were extracted from the exposure-corrected hard- and soft-band images within circular regions centered on the WAVDETECT positions. The apertures were scaled to mimic the degradation of the Chandra PSF with off-axis angle in each band, and had minimum radii of 10 pixels. Background counts were estimated based on extracting form source-free regions in annuli around each source.

Hardness_Ratio_Error
The RMS uncertainty in the hardness ratio HR.


Contact Person

Questions regarding the ELAISCXO database table can be addressed to the HEASARC User Hotline.

Page Author: Browse Software Development Team
Last Modified: 27-Feb-2007