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A Joint Model of the X-Ray and Infrared Extragalactic Backgrounds. I. Model Construction and First Results

Shi, Yong and Helou, George and Armus, Lee and Stierwalt, Sabrina and Dale, Daniel (2013) A Joint Model of the X-Ray and Infrared Extragalactic Backgrounds. I. Model Construction and First Results. Astrophysical Journal, 764 (1). Art. No. 28. ISSN 0004-637X.

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We present an extragalactic population model of the cosmic background light to interpret the rich high-quality survey data in the X-ray and IR bands. The model incorporates star formation and supermassive black hole (SMBH) accretion in a co-evolution scenario to fit simultaneously 617 data points of number counts, redshift distributions, and local luminosity functions (LFs) with 19 free parameters. The model has four main components, the total IR LF, the SMBH accretion energy fraction in the IR band, the star formation spectral energy distribution (SED), and the unobscured SMBH SED extinguished with a H I column density distribution. As a result of the observational uncertainties about the star formation and SMBH SEDs, we present several variants of the model. The best-fit reduced χ2 reaches as small as 2.7-2.9 of which a significant amount (>0.8) is contributed by cosmic variances or caveats associated with data. Compared to previous models, the unique result of this model is to constrain the SMBH energy fraction in the IR band that is found to increase with the IR luminosity but decrease with redshift up to z ~ 1.5; this result is separately verified using aromatic feature equivalent-width data. The joint modeling of X-ray and mid-IR data allows for improved constraints on the obscured active galactic nucleus (AGN), especially the Compton-thick AGN population. All variants of the model require that Compton-thick AGN fractions decrease with the SMBH luminosity but increase with redshift while the type 1 AGN fraction has the reverse trend.

Item Type:Article
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URLURL TypeDescription
Dale, Daniel0000-0002-5782-9093
Additional Information:© 2013 American Astronomical Society. Received 2012 July 30; accepted 2012 November 10; published 2013 January 22. We thank the anonymous referee for detailed and constructive comments. We thank Matthieu Bethermin for careful reading and comments. The work is supported through the Spitzer 5MUSES Legacy Program 40539. The authors acknowledge support by NASA through awards issued by JPL/Caltech.
Group:Infrared Processing and Analysis Center (IPAC)
Funding AgencyGrant Number
Spitzer 5MUSES Legacy Program40539
Subject Keywords:galaxies: active; galaxies: evolution; galaxies: luminosity function, mass function
Record Number:CaltechAUTHORS:20130308-134657854
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Official Citation:A Joint Model of the X-Ray and Infrared Extragalactic Backgrounds. I. Model Construction and First Results Yong Shi et al. 2013 ApJ 764 28
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:37422
Deposited By: Jason Perez
Deposited On:09 Mar 2013 00:00
Last Modified:17 Aug 2017 04:09

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