Spitzer Space Telescope - General Observer Proposal #20623


The bolometric output of luminous obscured AGN

Principal Investigator: Andrea Comastri
           Institution: INAF-Bologna, Italy

Co-Investigators: 
Cristian Vignali, Dipartimento di Astronomia, Bologna, Italy          
Francesca Pozzi, INAF- Bologna, Italy                                 
Francesca Civano, Dipartimento di Astronomia, Bologna, Italy          
Lucia Pozzetti, INAF-Bologna, Italy                                   
Marco Mignoli, INAF-Bologna, Italy                                    
Carlotta Gruppioni, INAF-Bologna, Italy                               
Marcella Brusa, Max-Planck-Institut für extraterrestrische Physik,    
Fabrizio Fiore, INAF-Roma, Italy                                      
Paolo Ciliegi, INAF-Bologna, Italy                                    
Roberto Maiolino, INAF-Arcetri, Italy                                 
Giovanni Zamorani, INAF-Bologna, Italy                                

Science Category: AGN/quasars/radio galaxies 
 Observing Modes: IracMap MipsPhot 
  Hours Approved: 44.9 

Abstract:
We propose Spitzer observations with both IRAC and MIPS of a well
defined sample of hard X-ray selected obscured AGN serendipitously
discovered by XMM-Newton in the 2-10  keV band.  The key scientific
issues we plan to address with the proposed broad-band infrared
observations are:  (a) A solid estimate of the bolometric luminosity
of accretion-powered, obscured sources and of the correlations between
hard X-ray properties (luminosity, obscuration, spectral slope) and
infrared spectral energy distribution.  (b) To recover the nuclear
spectral energy distribution of those AGN for which the presence of
supermassive black hole is inferred from the X-ray emission but which
remains elusive from observations at optical-UV and near-infrared
wavelengths.  (c) A probe of the physical status of the dense
circumnuclear matter responsible of the X-ray obscuration and dust
reprocessed infrared emission by comparison with the AGN unified model
predictions.  The proposed sample, selected from a shallow, large
area, hard X-ray survey (HELLAS2XMM), contains the most luminous
members of the population of highly obscured AGN responsible for the
X-ray background.  It is thus well suited for a pilot Spitzer program
(40  hours) which will allow us to investigate the so far poorly known
spectral energy distribution of luminous, obscured Type II quasars in
the mid-and far-infrared domains.