CHAMPHXAGN - CHAMP (Chandra Multiwavelength Project) Hard X-Ray Emitting AGN

Overview

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 erg/cm²/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 10⁴² erg 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 = 10⁴² erg 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 erg cm^-2 s^-1, r' < 22.5, and L_X > 10⁴² erg s^-1. The authors removed five objects identified as clusters based on their extended X-ray emission.

Catalog Bibcode

2005ApJ...618..123S

References

Hard X-ray-emitting active galactic nuclei selected by the Chandra
Multiwavelength Project.
    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)

Provenance

This table was created by the HEASARC in March 2007 based on the CDS table J/ApJ/618/123, file table4.dat.

Parameters

Source_Number
A running number for the X-ray source which uniquely identifies the source.

Source_Flag
This flag parameter is set 'e' to indicate that the source fell near the chip gap, and that no spectral fitting was performed.

Name
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).

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.

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 table.

LII
The Galactic Longitude of the X-ray source.

BII
The Galactic Latitude of the X-ray source.

Counts
The background-subtracted counts of the X-ray source in the observed frame 2.5 - 8.0 keV band.

Counts_Error
The uncertainty in the source counts.

Flux
The Galactic absorption-corrected observed-frame flux of the X-ray source in the 2.0 - 8.0 keV band, in units of erg cm^-2 s^-1.

Hardness_Ratio_Limit
This parameter is a limit flag for the hardness ratio of the X-ray source.

Hardness_Ratio
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)

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

Log_Lx
The logarithm of the rest-frame 2 - 8 keV luminosity of the X-ray source, in erg/s.

Rmag
The SDSS r' filter magnitude of the optical counterpart to the X-ray source.

GI_Color_Limit
This parameter is a limit flag for the g'-i' color of the optical counterpart to the X-ray source.

GI_Color
The SDSS g'-i' color of the optical counterpart to the X-ray source.

RI_Color_Limit
This parameter is a limit flag for the r'-i' color of the optical counterpart to the X-ray source.

RI_Color
The SDSS r'-i' color of the optical counterpart to the X-ray source.

Broad_Type
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.

Log_NH_Limit
This parameter is a limit flag for the best-fit values of log N_H for the X-ray source spectrum.

Log_NH
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 each object.

Log_NH_Pos_Err
The positive error in the value of log N_H, where N_H is in H atoms cm^-2.

Log_NH_Neg_Err
The negative error in the value of log N_H, where N_H is in H atoms cm^-2.

Class
The HEASARC Browse object classification, based on the value of the broad_type parameter.

Contact Person

Questions regarding the CHAMPHXAGN database table can be addressed to the HEASARC Help Desk.

Page Author: Browse Software Development Team
Last Modified: Monday, 16-Sep-2024 17:25:36 EDT