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GWSSTRPCXO - Groth-Westphal Strip Chandra X-Ray Point Source Catalog

HEASARC
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Overview

This table contains the optical and X-ray spectral properties of the sources detected in a 200-ks Chandra observation of part of the Groth-Westphal Strip (GWS) region, using the ACIS-I instrument. The authors present a relatively simple method for the detection of X-ray point sources and the calculation of limiting sensitivities, which they argue is at least as sensitive and more self-consistent than previous methods presented in the literature. A total of 158 distinct X-ray sources are included in this point-source catalogue in the ACIS-I area with a threshold Poisson detection probability of 4 x 10^-6. The number counts show a relative dearth of X-ray sources in this region.

A wealth of optical photometric and spectroscopic data are available in this field providing optical identifications and redshift determinations for the X-ray population. The optical photometry and spectroscopy used here are primarily from the Deep Extragalactic Evolutionary Probe 2 (DEEP2) survey with additional redshifts obtained from the literature. These are complemented with the deeper (r ~ 26 mag) multiwaveband data (ugriz) from the Canada-France-Hawaii Telescope Legacy Survey to estimate photometric redshifts and to optically identify sources fainter than the DEEP2 magnitude limit (R_AB ~ 24.5 mag). The authors focus their study on the 2 - 10 keV selected sample comprising 97 sources to the flux limit ~8 x 10^-16 erg/s/cm^2, this being the most complete in terms of optical identification rate (86 per cent) and redshift determination fraction (63 per cent; both spectroscopic and photometric).

Chandra observed the GWS, which is part of the Extended Groth Strip (EGS) region, on three separate occasions between 2002 August 11 and 22, using ACIS-I as the prime instrument. The S2 and S3 chips of the ACIS-S array were also operating during the observation, but as these are far off-axis their data are not considered further. The sequence number identifying the observations was 900144 and the three observation ID numbers (3305 on 2002-08-11, 4357 on 2002-08-12, and 4365 on 2002-08-21).


Catalog Bibcodes

2005MNRAS.356..568N
2006MNRAS.371..221G

References

A deep Chandra survey of the Groth Strip - I. The X-ray data.
    Nandra K., Laird E.S., Adelberger K., Gardner J.P., Mushotzky R.F.,
    Rhodes J., Steidel C.C., Teplitz H.I., Arnaud K.A.
   <Mon. Not. R. Astron. Soc., 356, 568-586 (2005)>
   =2005MNRAS.356..568N
A deep Chandra survey of the Groth Strip - II. Optical identification of
    the X-ray sources.
    Georgakakis A., Nandra K., Laird E.S., Gwyn S., Steidel C.C.,
    Sarajedini V.L., Barmby P., Faber S.M., Coil A.L., Cooper M.C., Davis M.,
    Newman J.A.
   <Mon. Not. R. Astron. Soc., 371, 221-234 (2006)>
   =2006MNRAS.371..221G

Provenance

This table was created by the HEASARC in July 2007 based on the merger of CDS Catalog J/MNRAS/356/568 file table3.dat and CDS Catalog J/MNRAS/371/221 file table2.dat.

Parameters

Source_Number
A running X-ray source number in order of increasing J2000.0 Right Ascension. The prefix 'c' reproduced here was used for all these sources in Paper I so as to distinguish them from sources from 2 comparison fields not included in the main GWS catalog.

Alt_Name
An alternative designation for the X-ray source using the '[NLA2005]' prefix (for Nandra, Laird, Adelberger 2005) and the value of the source number parameter, as recommended by the CDS Dictionary of Nomenclature of Celestial Objects.

Name
The preferred designation for the X-ray source using the 'CXOGWS' prefix (for Chandra X-Ray Observatory, Groth Westphal Survey) and the J2000.0 coordinates (JHHMMSS.s+DDMMSS), as recommended by 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 table (Table 2 of Paper II).

Dec
The Declination of the X-ray source in the selected equinox. This was given in J2000.0 coordinates to a precision of 0.01 aecseconds in the original table (Table 2 of Paper II).

LII
The Galactic Longitude of the X-ray source.

BII
The Galactic Latitude of the X-ray source.

Counts
The full-band (0.5 - 7 keV) counts for the X-ray source, extracted using a circular aperture of radius equal to the point spread function 90 per cent encircled energy fraction and subtracting background counts from a surrounding annulus.

Counts_Pos_Err
The positive error in the full-band counts for the X-ray source, calculated according to the Gehrels (1986, ApJ, 303, 336) prescription.

Counts_Neg_Err
The negative error in the full-band counts for the X-ray source, calculated according to the Gehrels (1986, ApJ, 303, 336) prescription.

SB_Counts_Limit
This flag parameter is set to '<' if the quoted soft-band counts for the X-ray source is an upper limit.

SB_Counts
The soft-band (0.5 - 2 keV) counts for the X-ray source, extracted using a circular aperture of radius equal to the point spread function 95 per cent encircled energy fraction (Alexander et al. 2003, AJ, 126, 539) and subtracting background counts from a surrounding annulus.

SB_Counts_Pos_Err
The positive error in the soft-band counts for the X-ray source, calculated according to the Gehrels (1986, ApJ, 303, 336) prescription.

SB_Counts_Neg_Err
The negative error in the soft-band counts for the X-ray source, calculated according to the Gehrels (1986, ApJ, 303, 336) prescription.

HB_Counts_Limit
This flag parameter is set to '<' if the quoted hard-band counts for the X-ray source is an upper limit.

HB_Counts
The hard-band (2 - 7 keV) counts for the X-ray source, extracted using a circular aperture of radius equal to the point spread function 90 per cent encircled energy fraction and subtracting background counts from a surrounding annulus.

HB_Counts_Pos_Err
The positive error in the hard-band counts for the X-ray source, calculated according to the Gehrels (1986, ApJ, 303, 336) prescription.

HB_Counts_Neg_Err
The negative error in the hard-band counts for the X-ray source, calculated according to the Gehrels (1986, ApJ, 303, 336) prescription.

UHB_Counts_Limit
This flag parameter is set to '<' if the quoted ultrahard-band counts for the X-ray source is an upper limit.

UHB_Counts
The ultrahard-band (4 - 7 keV) counts for the X-ray source, extracted using a circular aperture of radius equal to the point spread function 90 per cent encircled energy fraction and subtracting background counts from a surrounding annulus.

UHB_Counts_Pos_Err
The positive error in the ultrahard-band counts for the X-ray source, calculated according to the Gehrels (1986, ApJ, 303, 336) prescription.

UHB_Counts_Neg_Err
The negative error in the ultrahard-band counts for the X-ray source, calculated according to the Gehrels (1986, ApJ, 303, 336) prescription.

Flux
The flux of the X-ray source in the 0.5 - 10 keV energy band, in erg/s/cm^2.

Flux_Pos_Err
The positive error in the 0.5 - 10 keV flux, in erg/s/cm^2.

Flux_Neg_Err
The negative error in the 0.5 - 10 keV flux, in erg/s/cm^2.

SB_Flux_Limit
This flag parameter is set to '<' if the quoted 0.5 - 2 keV flux of the X-ray source is an upper limit.

SB_Flux
The flux of the X-ray source in the 0.5 - 2 keV energy band, in erg/s/cm^2.

SB_Flux_Pos_Err
The positive error in the 0.5 - 2 keV flux, in erg/s/cm^2.

SB_Flux_Neg_Err
The negative error in the 0.5 - 2 keV flux, in erg/s/cm^2.

HB_Flux_Limit
This flag parameter is set to '<' if the quoted 2 - 10 keV flux of the X-ray source is an upper limit.

HB_Flux
The flux of the X-ray source in the 2 - 10 keV energy band, in erg/s/cm^2.

HB_Flux_Pos_Err
The positive error in the 2 - 10 keV flux, in erg/s/cm^2.

HB_Flux_Neg_Err
The negative error in the 2 - 10 keV flux, in erg/s/cm^2.

UHB_Flux_Limit
This flag parameter is set to '<' if the quoted 5 - 10 keV flux of the X-ray source is an upper limit.

UHB_Flux
The flux of the X-ray source in the 5 - 10 keV energy band, in erg/s/cm^2.

UHB_Flux_Pos_Err
The positive error in the 5 - 10 keV flux, in erg/s/cm^2.

UHB_Flux_Neg_Err
The negative error in the 5 - 10 keV flux, in erg/s/cm^2.

Log_Pmin
The decimal logarithm of the lowest false detection probability found for the four energy bands. A probability of 1.0^-8 was assigned if the Poisson probability was less than this value.

Off_Axis
The off-axis angle of the X-ray source, in arcminutes.

Hardness_Ratio
The hardness ratio HR of the X-ray source, defined as HR = (H-S)/(H+S), where H and S are the 2 - 7 keV and the 0.5 - 2 keV counts, respectively, corrected to their on-axis values.

Source_Flags
This parameter contains flags indicating in which of the bands (fshu) the X-ray source was detected at < 4 x 10^-6 probability, where the counts band codes s are full (f), soft (s), hard (h) and ultra-hard (u), and the first band quoted is the one with the lowest (most significant) probability.

Offset
The X-ray versus optical source centroid offset, in arcseconds.

Prob_Random_Limit
This parameter is set to '<' if the quoted probability that the optical counterpart to the X-ray source is spurious is an upper limit.

Prob_Random
The probability that the optical counterpart to the X-ray source is a spurious alignment, in percent.

Rmag_Limit
This parameter is set to '>' if the quoted probability R magnitude is an upper limit to the actual magnitude. Note that the HEASARC changed the '<' values in the printed and CDS version of this catalog to the '>' values given here.

Rmag
The R magnitude in the AB system of the optical counterpart to the X-ray source.

Ref_Optical_ID
The source of the optical identification coded as follows:

        1 = DEEP2 (2nd Deep Extragalactic Evolutionary Probe survey)
        2 = Steidel et al. (2003, CDS Cat. <J/ApJ/592/728>)
        3 = CFHTLS (Canada-France-Hawaii Telescope Legacy Survey)
  

Redshift
The spectroscopic redshift of the optical counterpart to the X-ray source.

Ref_Redshift
Th reference code for the source of the spectroscopic redshift, coded as follows:

        1 = DEEP2 (2nd Deep Extragalactic Evolutionary Probe survey)
        2 = DEEP (Weiner et al., 2005ApJ...620..595W)
        3 = CFRS (Lilly et al. 1995, CDS Cat. <VII/225>)
        4 = Steidel et al. (2003, CDS Cat. <J/ApJ/592/728>))
        5 = SDSS, (Sloan Digital Sky Survey, CDS Cat. <II/276>)
  

Source_Type
The spectroscopic classification of the optical counterpart to the X-ray source, coded as follows:

       NL = narrow emission lines
       BL = broad emission lines
       AB = absorption lines
     UNCL = no classification available
     STAR = Galactic star
  

Phot_Redshift
The photometric redshift of the optical counterpart to the X-ray source, estimated as discussed in Section 4 of Paper II.

Phot_Redshift_Pos_Err
The positive error in the photometric redshift.

Phot_Redshift_Neg_Err
The negative error in the photometric redshift.

NH_Limit
This parameter is set to '<' if the quoted absorption column density is an upper limit.

NH
The absorbing hydrogen column density n_H in atoms cm^-2, inferred from the X-ray spectral analysis as discussed in Section 5 of Paper II.

NH_Pos_Err
The positive error in n_H, in atoms cm^-2.

NH_Neg_Err
The negative error in n_H, in atoms cm^-2.

Lx
The unobscured 0.5 - 10 keV X-ray luminosity of the source, in erg/s.


Contact Person

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

Page Author: Browse Software Development Team
Last Modified: 30-Jul-2007