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Spitzer power-law active galactic nucleus candidates in the chandra deep field-north

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Donley, J. L. and Rieke, G. H. and Pérez González, Pablo Guillermo and Rigby, J. R. and Alonso Herrero, A. (2007) Spitzer power-law active galactic nucleus candidates in the chandra deep field-north. Astrophysical journal, 660 (1). pp. 167-190. ISSN 0004-637X

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Official URL: http://dx.doi.org/10.1086/512798


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Abstract

We define a sample of 62 galaxies in the Chandra Deep Field-North whose Spitzer IRAC SEDs exhibit the characteristic power-law emission expected of luminous AGNs. We study the multiwavelength properties of this sample and compare the AGNs selected in this way to those selected via other Spitzer color-color criteria. Only 55% of the power-law galaxies are detected in the X-ray catalog at exposures of >0.5 Ms, although a search for faint emission results in the detection of 85% of the power-law galaxies at the ≥2.5 σ detection level. Most of the remaining galaxies are likely to host AGNs that are heavily obscured in the X-ray. Because the power-law selection requires the AGNs to be energetically dominant in the near- and mid-infrared, the power-law galaxies comprise a significant fraction of the Spitzer-detected AGN population at high luminosities and redshifts. The high 24 μm detection fraction also points to a luminous population. The power-law galaxies comprise a subset of color-selected AGN candidates. A comparison with various mid-infrared color selection criteria demonstrates that while the color-selected samples contain a larger fraction of the X-ray-luminous AGNs, there is evidence that these selection techniques also suffer from a higher degree of contamination by star-forming galaxies in the deepest exposures. Considering only those power-law galaxies detected in the X-ray catalog, we derive an obscured fraction of 68% (2 : 1). Including all of the power-law galaxies suggests an obscured fraction of <81% (4 : 1).


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© 2007 The American Astronomical Society. All rights reserved.
This work was supported by an NSF Graduate Research Fellowship and by NASA through contract 1255094 issued by JPL/California Institute of Technology. We thank the referee for helpful comments that improved the paper.

Uncontrolled Keywords:Ultraluminous infrared galaxies; X-ray sources; Spectral energy-distributions; Star-forming galaxies; Medium sensitivity survey; Digital sky survey; μm spectroscopy; Space-telescope; Hellas2xmm survey; Radio properties
Subjects:Sciences > Physics > Astrophysics
Sciences > Physics > Astronomy
ID Code:38719
Deposited On:04 Aug 2016 17:21
Last Modified:10 Dec 2018 15:05

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