Volume 512, March-April 2010
|Number of page(s)||14|
|Published online||25 March 2010|
The X-ray to optical-UV luminosity ratio of X-ray selected type 1 AGN in XMM-COSMOS*
Dipartimento di Astronomia, Università di Bologna, via Ranzani 1, 40127 Bologna, Italy e-mail: email@example.com
2 INAF – Osservatorio Astronomico di Bologna, via Ranzani 1, 40127 Bologna, Italy
3 Max Planck Institut für extraterrestische Physik, Giessenbachstrasse 1, 85748 Garching, Germany
4 California Institute of Technology, MC 105-24, 1200 East California Boulevard, Pasadena, CA 91125, USA
5 Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138, USA
6 Excellence Cluster Universe, Boltzmannstr. 2, 85748 Garching, Germany
7 Steward Observatory, University of Arizona, 933 N Cherry Ave, Tucson, AZ 85721, USA
8 Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218, USA
9 Max Planck Institut für Astronomie, Königstuhl 17, 69117 Heidelberg, Germany
10 Institute for Astronomy, University of Hawaii, 2680 Woodlawn Drive, Honolulu, HI 96822-1839, USA
11 Department of Physics, ETH Zurich, 8093 Zurich, Switzerland
12 ESO, Karl-Schwarschild-Strasse 2, 85748 Garching, Germany
13 INAF – Osservatorio Astronomico di Roma, via Frascati 33, Monteporzio (Rm) 00040, Italy
14 Laboratoire d'Astrophysique de Marseille, OAMP, CNRS-Université Aix-Marseille, 38 rue Frédéric Joliot-Curie, 13388 Marseille Cedex 13, France
15 INAF – IASF, via Bassini 15, 20133 Milano, Italy
16 INAF – Osservatorio Astronomico di Brera, via Brera 28, 20121 Milan, Italy
17 Laboratoire d'Astrophysique de Toulouse-Tarbes, Université de Toulouse, CNRS, 14 avenue Edouard Belin, 31400 Toulouse, France
Accepted: 4 January 2010
We present a study of the X-ray to optical properties of a sample of 545 X-ray selected type 1 AGN, from the XMM-COSMOS survey, over a wide range of redshifts (0.04 < z < 4.25) and X-ray luminosities (40.6 ≤ Log ≤ 45.3). About 60% of them are spectroscopically identified type 1 AGN, while the others have a reliable photometric redshift and are classified as type 1 AGN on the basis of their multi-band Spectral Energy Distributions. We discuss the relationship between UV and X-ray luminosity, as parameterized by the spectral slope, and its dependence on redshift and luminosity. We compare our findings with previous investigations of optically selected broad-line AGN (mostly from SDSS). A highly significant correlation between and is found, in agreement with previous investigations of optically selected samples. We calculate bolometric corrections, kbol, for the whole sample using hard X-ray luminosities (), and the Eddington ratios for a subsample of 150 objects for which black hole mass estimates are available. We confirm the trend of increasing bolometric correction with increasing Eddington ratio as proposed in previous works. A tight correlation is found between and kbol, which can be used to estimate accurate bolometric corrections using only optical and X-ray data. We find a significant correlation between and Eddington ratio, in which the ratio between X-ray and optical flux decreases with increasing Eddington ratio.
Key words: galaxies: active / Galaxy: evolution / quasars: general / methods: statistical
Full Table 2 is only available in electronic form at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (184.108.40.206) or via http://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/512/A34
© ESO, 2010
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