THE FIELD X-RAY AGN FRACTION TO z = 0.7 FROM THE CHANDRA MULTIWAVELENGTH PROJECT AND THE SLOAN DIGITAL SKY SURVEY

Journal Article · Wed Nov 10 04:00:00 EST 2010 · Astrophysical Journal

DOI:https://doi.org/10.1088/0004-637X/723/2/1447· OSTI ID:21471252

Haggard, Daryl; Anderson, Scott F ^[1]; Green, Paul J; Aldcroft, Tom L; Kim, Dong-Woo ^[2]; Constantin, Anca ^[3]

---

1. Department of Astronomy, University of Washington, Box 351580, Seattle, WA 98195 (United States)
2. Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States)
3. Department of Physics and Astronomy, James Madison University, Harrisonburg, VA 22807 (United States)

We employ the Chandra Multiwavelength Project (ChaMP) and the Sloan Digital Sky Survey (SDSS) to study the fraction of X-ray-active galaxies in the field to z = 0.7. We utilize spectroscopic redshifts from SDSS and ChaMP, as well as photometric redshifts from several SDSS catalogs, to compile a Parent sample of more than 100,000 SDSS galaxies and nearly 1600 Chandra X-ray detections. Detailed ChaMP volume completeness maps allow us to investigate the local fraction of active galactic nuclei (AGNs), defined as those objects having broadband X-ray luminosities L{sub X} (0.5-8 keV) {>=}10{sup 42} erg s{sup -1}, as a function of absolute optical magnitude, X-ray luminosity, redshift, mass, and host color/morphological type. In five independent samples complete in redshift and i-band absolute magnitude, we determine the field AGN fraction to be between 0.16% {+-} 0.06% (for z {<=} 0.125 and -18>M{sub i} > - 20) and 3.80% {+-} 0.92% (for z {<=} 0.7 and M{sub i} < -23). We find excellent agreement between our ChaMP/SDSS field AGN fraction and the Chandra cluster AGN fraction, for samples restricted to similar redshift and absolute magnitude ranges: 1.19% {+-} 0.11% of ChaMP/SDSS field galaxies with 0.05 < z < 0.31 and absolute R-band magnitude more luminous than M{sub R} < -20 are AGNs. Our results are also broadly consistent with measures of the field AGN fraction in narrow, deep fields, though differences in the optical selection criteria, redshift coverage, and possible cosmic variance between fields introduce larger uncertainties in these comparisons.

• OSTI ID: 21471252
• Journal Information: Astrophysical Journal, Journal Name: Astrophysical Journal Journal Issue: 2 Vol. 723; ISSN ASJOAB; ISSN 0004-637X
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTRONOMY AND ASTROPHYSICS
COLOR
COSMIC RAY SOURCES
COSMIC X-RAY SOURCES
DETECTION
ELECTROMAGNETIC RADIATION
ENERGY RANGE
GALAXIES
GALAXY NUCLEI
IONIZING RADIATIONS
KEV RANGE
KEV RANGE 01-10
LUMINOSITY
OPTICAL PROPERTIES
ORGANOLEPTIC PROPERTIES
PHYSICAL PROPERTIES
RADIATION DETECTION
RADIATIONS
RED SHIFT
X RADIATION
X-RAY DETECTION
X-RAY GALAXIES