CHAMPHXAGN - CHAMP (Chandra Multiwavelength Project) Hard X-Ray Emitting AGN
This table contains the results from an X-ray and optical analysis
of 188 active galactic nuclei (AGN) identified from 497 hard X-ray
(observed flux in the (2.0 - 8.0 keV) band > 2.7 x 10^-15 ergs/cm^2/s)
sources in 20 Chandra fields (1.5 square degrees) forming part of the
Chandra Multiwavelength Project (ChaMP). These medium-depth X-ray observations
enable the detection of a representative subset of those sources responsible
for the bulk of the 2 - 8 keV cosmic X-ray background. Brighter than the
survey's optical spectroscopic limit, the authors achieve a reasonable degree
of completeness (77% of X-ray sources with counterparts r' < 22.5 have been
classified): broad emission-line AGNs (62%), narrow emission-line galaxies
(24%), absorption-line galaxies (7%), stars (5%), or clusters (2%).
To construct a pure AGN sample, the authors required the rest-frame 2.0-8.0
keV luminosity (uncorrected for intrinsic absorption) to exceed 10^42 ergs
s^-1, thereby excluding any sources that may contain a significant stellar
or hot ISM component. The most luminous known star-forming or elliptical
galaxies attain at most L_X = 10^42 ergs s^-1. Since many of the traditional
optical AGN signatures are not present in obscured sources, high X-ray
luminosity becomes the authors' single discriminant for supermassive black
hole accretion. They believe that almost all of the NELGs and ALGs harbor
accreting SMBHs based on their X-ray luminosity. They find that 90% of the
identified ChaMP sources have luminosities above this threshold. These
selection criteria yield a sample of 188 AGNs from 20 Chandra fields with
f(2-8 keV) > 2.7 x 10-15 ergs cm^-2 s^-1, r' < 22.5, and L_X > 10^42 ergs s^-1.
The authors removed five objects identified as clusters based on their
extended X-ray emission.
Hard X-ray-emitting active galactic nuclei selected by the Chandra
Silverman J.D., Green P.J., Barkhouse W.A., Kim D.-W., Aldcroft T.L.,
Cameron R.A., Wilkes B.J., Mossman A., Ghosh H., Tananbaum H., Smith M.G.,
Smith R.C., Smith P.S., Foltz C., Wik D., Jannuzi B.T.
<Astrophys. J., 618, 123-138 (2005)>
=2005ApJ...618..123S (SIMBAD/NED BibCode)
This table was created by the HEASARC in March 2007 based on the
CDS table J/ApJ/618/123, file table4.dat.
A running number for the X-ray source which uniquely
identifies the source.
This flag parameter is set 'e' to indicate that the source fell
near the chip gap, and that no spectral fitting was performed.
The designation for objects in ChaMP, as registered with the CDS
Dictionary of Nomenclature of Celestial Objects, using the 'CXOMP' prefix
for Chandra X-Ray Observatory Multiwavelength Project and the J2000.0 source
coordinates (JHHMMSS.s+DDMMSS or JHHMMSS.s-DDMMSS).
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.
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
The Galactic Longitude of the X-ray source.
The Galactic Latitude of the X-ray source.
The background-subtracted counts of the X-ray source in the observed
frame 2.5 - 8.0 keV band.
The uncertainty in the source counts.
The Galactic absorption-corrected observed-frame flux of the X-ray
source in the 2.0 - 8.0 keV band, in units of ergs cm^-2 s^-1.
This parameter is a limit flag for the hardness ratio
of the X-ray source.
The hardness ratio HR of the X-ray source, defined as
HR=(H-S)/(H+S), where S are the counts in the soft band (0.3 - 2.5 keV) and H
the counts in the hard band (2.5 - 8.0 keV)
The redshift of the optical counterpart to the X-ray source.
The logarithm of the rest-frame 2 - 8 keV luminosity of the X-ray
source, in erg/s.
The SDSS r' filter magnitude of the optical counterpart to the X-ray
This parameter is a limit flag for the g'-i' color of the
optical counterpart to the X-ray source.
The SDSS g'-i' color of the optical counterpart to the X-ray
This parameter is a limit flag for the r'-i' color of the
optical counterpart to the X-ray source.
The SDSS r'-i' color of the optical counterpart to the X-ray
The class of the optical counterpart using classification scheme
of optical spectra similar to that used in the Einstein Observatory Extended
Medium-Sensitivity Survey (Stocke et al. 1991, ApJS, 76, 813). Objects with
strong emission lines (equivalent widths > 5 Angstroms) are classified as
either broad-line AGNs (BLAGNs; FWHM > 1000 km s^-1) or narrow emission-line
galaxies (NELGs; FWHM < 1000 km s^-1). Counterparts with weak emission line or
pure absorption line spectra are classified as absorption line galaxies (ALGs).
Any stellar source is labeled as a STAR. For the ALGs, the authors measured
the Ca II break "CONTRAST" (Stocke et al. 1991) to look for a power-law AGN
component to the continuum to note potential BL Lac candidates. If the
associated X-ray emission was extended, the object was further labeled as
a possible cluster member.
This parameter is a limit flag for the best-fit values of
log N_H for the X-ray source spectrum.
The logarithm of the best-fit absorption column density, in H atoms
cm^-2. Spectral fitting was done using the CIAO Sherpa tool. For all sources,
the authors fit an absorbed power law containing an intrinsic absorber with
a neutral column N_H at the source redshift. Their choice of photon index
(frozen at Gamma = 1.9) was based on previous studies of unabsorbed AGNs.
This N_H fit provided a robust one-parameter characterization of the intrinsic
spectral shape for as few as 10 counts. The authors verified by an extensive
Monte Carlo simulation that the parameter uncertainties calculated with
projection of confidence contours in Sherpa were reliable. Note that the
spectral model contained a fixed Galactic neutral absorber appropriate for
The positive error in the value of log N_H, where N_H is
in H atoms cm^-2.
The negative error in the value of log N_H, where N_H is
in H atoms cm^-2.
The HEASARC Browse object classification, based on the value of
the broad_type parameter.
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