ROS13HRCXO - ROSAT/XMM-Newton 13-hour Field Chandra X-Ray Source Catalog
The majority of the identifications are with galaxies. As found in other Chandra surveys, there is a very wide range of optical magnitudes for a given X-ray flux, implying a range of emission mechanisms, and many sources have high LX/Lopt ratios, implying absorption at moderate redshift. Comparison with the earlier ROSAT survey shows that the accuracy of the ROSAT positions agrees very well with the predictions from simulations by McHardy et al. and that the large majority of the identifications were correct.
A medium-deep Chandra and Subaru survey of the 13-h XMM/ROSAT deep survey area. McHardy I.M., Gunn K.F., Newsam A.M., Mason K.O., Page M.J., Takata T., Sekiguchi K., Sasseen T., Cordova F., Jones L.R., Loaring N. <Mon. Not. R. Astron. Soc. 342, 802 (2003)> =2003MNRAS.342..802M
A unique identification number for each Chandra X-ray source in the catalog, in order of decreasing Chandra X-ray flux.
The designation of the Chandra X-ray source, using the prefix '[MGN2003]' (for McHardy, Gunn, Newsam 2003) and the Chandra source number for these names, in accordance with the naming convention recommended by the Dictionary of Nomenclature of Celestial Objects.
This flag parameter contains codes for individual notes on the source, as follows:
a = Optical position is taken direct from the APM scan of the POSS-II plates and magnitude is from UH imaging. c = Magnitude taken from CFHT image. For source 114 we give the coordinates of a very faint object which is not visible on the CFHT image but which is visible on a deep B-band image (Croom, private communication). Sources 99 and 114, the identifications of which are unreliable because of the lower-sensitivity imaging, are not included in any statistical analysis. o = Optical counterpart is not deblended properly by SExtractor software so the coordinates and magnitude, but not stellarity or FWHM, are calculated manually.
This flag parameter has non-blank values to indicate that there are alternative optical candidates for the X-ray source than the one listed in this table:
U = the true identification is uncertain. P = the primary identification is probably correct but SExtractor did pick up another, less likely, candidate within 2 arcsec of the Chandra centroid. The primary candidate is chosen, unless stated otherwise, on the basis of being closer to the Chandra centroid and being brighter.Information about these alternative counterparts is given in Table A1 and Appendix A of the reference paper.
The broad-band 0.5 - 7.0 keV flux of the Chandra X-ray source, in erg/s/cm2. Fluxes are determined from the maximum likelihood (ML) parameters of the Cash statistic, where count rate is a free parameter. These count rates automatically compensate for the variation in the point-spread function (PSF) and the complicate exposure map of the observations. The ML count rates are then converted to these X-ray fluxes by assuming a power-law spectrum with an energy spectral index of 0.4 and a Galactic absorption of 6.5 x 1019 cm-2.
The Cash chi-squared likelihood statistic C for the Chandra X-ray source. The threshold for detection of C = 25 approximates to 5 sigma.
The Right Ascension of the centroid of the Chandra X-ray source in the selected equinox. This was given in J2000 equatorial coordinates and to a precision of 0.01 seconds of time in the original source table.
The Declination of the of the centroid Chandra X-ray source in the selected equinox. This was given in J2000 equatorial coordinates and to a precision of 0.01 arcseconds in the original source table.
The Galactic Longitude of the Chandra X-ray source centroid.
The Galactic Latitude of the Chandra X-ray source centroid.
The optical-Chandra positional offset (in that sense) in the Right Ascension direction for the primary optical identification listed here, in arcseconds.
The optical-Chandra positional offset (in that sense) in the Declination direction for the primary optical identification listed here, in arcseconds.
The total optical-Chandra positional offset for the primary optical identification listed here, in arcseconds.
This parameter is a limit flag for the R-magnitude of the optical counterpart, either '>' or ">='.
The R-band magnitude of the optical counterpart of the Chandra X-ray source.
The off-axis angle of the Chandra X-ray source, in arcminutes.
The off-axis angle of the X-ray source in the ROSAT and XMM-Newton observations, in arcminutes.
The full width at half maximum (FWHM) of the optical counterpart to the Chandra X-ray source, in arcseconds.
The stellarity of the optical counterpart to the Chandra X-ray source, where values closer to 0.00 imply extended, e.g., a galaxy, and values closer to 1.00 imply point-like, e.g., a star.
The corresponding ROSAT source number for the X-ray source as given in McHardy et al. (1998, MNRAS, 295, 641).
The Right Ascension of the corresponding ROSAT source in the selected equinox as given in McHardy et al. (1998, MNRAS, 295, 641).
The Declination of the corresponding ROSAT source in the selected equinox as given in McHardy et al. (1998, MNRAS, 295, 641).
The total offset between the ROSAT and Chandra X-ray source positions, in arcseconds.
The total offset between the proposed ROSAT optical counterpart given in McHardy et al. (1998, MNRAS, 295, 641) and the Chandra X-ray source positions, in arcseconds.
The classification of the proposed ROSAT optical counterpart given in McHardy et al. (1998, MNRAS, 295, 641), coded as follows:
BLANK = no classification CLU = cluster G/NELG = Galaxy/narrow-emission-line galaxies G/QSO? = Galaxy/quasar ? GAL? = Galaxy ? GP/GAL = Galaxy pair/galaxy GRP = Group of galaxies GSTAR = G star KSTAR? = K star ? MSTAR = M star NELG = narrow-emission-line galaxies QSO = quasar
The redshift of the proposed ROSAT optical counterpart as given in McHardy et al. (1998, MNRAS, 295, 641)
The parameter indicating the confidence in the classification of the proposed ROSAT optical counterpart, as given in McHardy et al, (1998, MNRAS, 295, 641), coded as follows:
C = certain (code was '*' in McHardy et al 1998) L = likely (code was '(*)' in McHardy et al 1998) P = possible (code was ' ' in McHardy et al 1998)
This flag parameter indicates whether or not the optical counterpart to the ROSAT X-ray source proposed in McHardy et al. (1998, MNRAS, 295, 641) has been confirmed, as follows:
Y = optical counterpart is < 1" from the Chandra source when the Chandra off-axis angle OffC is < 6' (extended to < 1.6" for 6 < OffC < 8') N = optical counterpart is > 3" from the Chandra source ? = all intermediate cases