AGNSDSSXMM - SDSS/XMM-Newton AGN Spectral Properties Catalog
Bright XMM-Newton data are combined with the Chandra Deep Field
South observations to explore the behavior of the intrinsic AGN absorption,
as a function of redshift and luminosity. The sample consists of 359
sources selected in the hard 2 - 8 keV band, spanning the flux range
from 6 x 10^-16 - 3 x 10^-13 erg/cm^2/s with a high rate of spectroscopic or
photometric redshift completeness (100 and 85 per cent for the Chandra and
XMM-Newton data, respectively). The authors derive the column density
values using X-ray spectral fits. They find that the fraction of
obscured AGN falls with increasing luminosity in agreement with
previous findings. The fraction of obscured AGN shows an apparent
increase at high redshifts (z > 2). Simulations show that this effect
can most probably be attributed to the fact that at high redshifts the
column densities are overestimated.
This table contains the subset of 153 brighter hard X-ray sources in the
XMM-Newton/Sloan Digital Sky Survey (SDSS) sample which have 2-8 keV fluxes >
3 x 10^-14 erg cm^-2 s^-1, excluding a number of sources with extended optical
morphology and blue colors, as well as 4 sources with X-ray to optical
fluxes < 0.1 which are fit better with stellar rather than QSO templates.
XMM-Newton and Chandra measurements of the AGN intrinsic absorption:
dependence on luminosity and redshift.
Akylas A., Georgantopoulos I., Georgakakis A., Kitsionas S.,
<Astron. Astrophys., 459, 693-701 (2006)>
This table was created by the HEASARC in July 2007 based on CDS
Catalog J/A+A/459/693 file table2.dat.
A running X-ray source number in order of increasing J2000.0
The preferred designation for the X-ray source using the '[AGG2006]'
prefix (for Akylas, Georgantopoulos, Georgakakis, 2006) and the source number,
as recommended by the CDS Dictionary of Nomenclature of Celestial Objects.
The Right Ascension of the X-ray source in the selected equinox. This
was given in J2000.0 coordinates in decimal degrees to a precision of 0.001
degrees (3.6") in the original table.
The Declination of the X-ray source in the selected equinox. This was
given in J2000.0 coordinates in decimal degrees to a precision of 0.001 degrees
(3.6") in the original table.
The Galactic Longitude of the X-ray source.
The Galactic Latitude of the X-ray source.
The X-ray power-law photon index, Gamma. For sources with
adequate count statistics (net source counts >100), the authors used the
Chi-squared statistic technique. The data were grouped to give a minimum of 15
counts per bin to ensure that Gaussian statistics apply. The authors adopted
an absorbed power-law model and attempted to constrain the intrinsic absorption
column density n_H (i.e., having subtracted the Galactic absorption) and Gamma.
For the sources with limited photon statistics (net counts <100), they used the
C-statistic technique specifically developed to extract spectral information
from data with a low signal-to-noise ratio. In this case, the data were grouped
to give a minimum of 1 count per bin to avoid zero count bins. The authors
tried to constrain the intrinsic column densities using an absorbed power-law
model with Gamma fixed to 1.8. In both cases, the spectral fittings were
performed in the 0.3 - 8 keV energy band where the sensitivity of the
XMM-Newton detectors is the highest.
The positive error in the power-law photon index,
The negative error in the power-law photon index,
The upper or lower limit to the observed best-fit absorption
column density, n_H.
The observed best-fit value of the Hydrogen column density, n_H, in atoms
The positive error in the observed best-fit value of the Hydrogen
column density, n_H, in atoms cm^-2.
The negative error in the observed best-fit value of the Hydrogen
column density, n_H, in atoms cm^-2.
The intrinsic 2 - 8 keV flux of the X-ray source, in erg cm^-2 s^-1.
The redshift (either spectroscopic or photometric according to
the value of the opt_ctrprt_flag parameter) of the SDSS counterpart to the
The Galactic column density in the direction of the observed field,
(n_H)_Gal, in atoms cm^-2.
The intrinsic rest-frame column density, (n_H)_Int, in atoms
The logarithm of the intrinsic 2 - 8 keV luminosity of the source,
in erg s^-1.
This parameter flags the status of the optical counterpart
to the X-ray source:
1 = spectroscopic optical counterpart
2 = photometric optical counterpart
3 = absence of an optical counterpart
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