Ballantyne, D. R. and Draper, A. R. and Madsen, K. K. and Rigby, J. R. and Treister, E. (2011) Lifting the Veil on Obscured Accretion: Active Galactic Nuclei Number Counts and Survey Strategies for Imaging Hard X-Ray Missions. Astrophysical Journal, 736 (1). Art. No. 56. ISSN 0004-637X http://resolver.caltech.edu/CaltechAUTHORS:20110801-092506995
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Finding and characterizing the population of active galactic nuclei (AGNs) that produces the X-ray background (XRB) is necessary to connect the history of accretion to observations of galaxy evolution at longer wavelengths. The year 2012 will see the deployment of the first hard X-ray imaging telescope which, through deep extragalactic surveys, will be able to measure the AGN population at the energies where the XRB peaks (~20-30 keV). Here, we present predictions of AGN number counts in three hard X-ray bandpasses: 6-10 keV, 10-30 keV, and 30-60 keV. Separate predictions are presented for the number counts of Compton thick AGNs, the most heavily obscured active galaxies. The number counts are calculated for five different models of the XRB that differ in the assumed hard X-ray luminosity function, the evolution of the Compton thick AGNs, and the underlying AGN spectral model. The majority of the hard X-ray number counts will be Compton thin AGNs, but there is a greater than tenfold increase in the Compton thick number counts from the 6-10 keV to the 10-30 keV band. The Compton thick population shows enough variation that a hard X-ray number counts measurement will constrain the models. The computed number counts are used to consider various survey strategies for the NuSTAR mission, assuming a total exposure time of 6.2 Ms. We find that multiple surveys will allow a measurement of Compton thick evolution. The predictions presented here should be useful for all future imaging hard X-ray missions.
|Additional Information:||© 2011 American Astronomical Society. Received 2010 November 29; accepted 2011 May 4; published 2011 July 6. The author list is alphabetical; all authors contributed equally to this work. This work was supported in part by NSF award AST 1008067 to D.R.B. J.R. was supported by a Carnegie Fellowship at the Carnegie Observatories in Pasadena. Support for the work of E.T. was provided by the National Aeronautics and Space Administration through Chandra Post-doctoral Fellowship Award Number PF8-90055 issued by the Chandra X-ray Observatory Center, which is operated by the Smithsonian Astrophysical Observatory for and on behalf of the National Aeronautics Space Administration under contract NAS8-03060. The authors thank D. Alexander, F. Harrison, and D. Stern for comments.|
|Group:||Space Radiation Laboratory|
|Subject Keywords:||galaxies: active; galaxies: nuclei; galaxies: Seyfert; surveys; X-rays: diffuse background; X-rays: galaxies|
|Classification Code:||PACS: 98.54.Cm; 98.70.Qy; 98.62.Ai; 98.62.Mw; 98.62.Py|
|Official Citation:||Lifting the Veil on Obscured Accretion: Active Galactic Nuclei Number Counts and Survey Strategies for Imaging Hard X-Ray Missions D. R. Ballantyne et al. 2011 ApJ 736 56|
|Usage Policy:||No commercial reproduction, distribution, display or performance rights in this work are provided.|
|Deposited By:||Ruth Sustaita|
|Deposited On:||01 Aug 2011 16:56|
|Last Modified:||04 Mar 2013 22:37|
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