The HELLAS2XMM survey. X. The bolometric output of luminous obscured quasars: The Spitzer perspective

F. Pozzi; C. Vignali; A. Comastri; L. Pozzetti; M. Mignoli; C. Gruppioni; G. Zamorani; C. Lari; F. Civano; M. Brusa; F. Fiore; R. Maiolino; F. La Franca

doi:10.1051/0004-6361:20077092

arXiv · 0704.0735

The HELLAS2XMM survey. X. The bolometric output of luminous obscured quasars: The Spitzer perspective

F. Pozzi·C. Vignali·A. Comastri·L. Pozzetti·M. Mignoli·C. Gruppioni·G. Zamorani·C. Lari·F. Civano·M. Brusa·F. Fiore·R. Maiolino·F. La Franca

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Abstract

Aims: We aim at estimating the spectral energy distributions (SEDs) and the physical parameters related to the black holes harbored in eight high X-ray-to-optical (F_X/F_R>10) obscured quasars at z>0.9 selected in the 2--10 keV band from the HELLAS2XMM survey. Methods: We use IRAC and MIPS 24 micron observations, along with optical and Ks-band photometry, to obtain the SEDs of the sources. The observed SEDs are modeled using a combination of an elliptical template and torus emission (using the phenomenological templates of Silva et al. 2004) for six sources associated with passive galaxies; for two point-like sources, the empirical SEDs of red quasars are adopted. The bolometric luminosities and the M_BH-L_K relation are used to provide an estimate of the masses and Eddington ratios of the black holes residing in these AGN. Results: All of our sources are detected in the IRAC and MIPS (at 24 micron) bands. The SED modeling described above is in good agreement with the observed near- and mid-infrared data. The derived bolometric luminosities are in the range ~10^45-10^47 erg s^-1, and the median 2--10 keV bolometric correction is ~25, consistent with the widely adopted value derived by Elvis et al. (1994). For the objects with elliptical-like profiles in the K_s band, we derive high stellar masses (0.8-6.2)X10^11 Mo, black hole masses in the range (0.2-2.5)X10^9 Mo, and Eddington ratios L/L_Edd<0.1, suggesting a low-accretion phase.

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F. Pozzi, C. Vignali, A. Comastri, L. Pozzetti, M. Mignoli, C. Gruppioni, G. Zamorani, C. Lari, F. Civano, M. Brusa, F. Fiore, R. Maiolino, F. La Franca. 2007-04-05. The HELLAS2XMM survey. X. The bolometric output of luminous obscured quasars: The Spitzer perspective. https://doi.org/10.1051/0004-6361:20077092

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