24 micron Properties of X-ray Selected AGN

J. R. Rigby; G. H. Rieke; R. Maiolino; R. Gilli; C. Papovich; P. G. Perez-Gonzalez; A. Alonso-Herrero; E. Le Floc'h; C. W. Engelbracht; K. Gordon; D. C. Hines; J. L. Hinz; J. E. Morrison; J. Muzerolle; M. J. Rieke; K. Y. Su

arXiv · astro-ph/0406029

24 micron Properties of X-ray Selected AGN

J. R. Rigby·G. H. Rieke·R. Maiolino·R. Gilli·C. Papovich·P. G. Perez-Gonzalez·A. Alonso-Herrero·E. Le Floc'h·C. W. Engelbracht·K. Gordon·D. C. Hines·J. L. Hinz·J. E. Morrison·J. Muzerolle·M. J. Rieke·K. Y. Su

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Abstract

We examine the 24 micron to X-ray color of 157 X-ray--selected AGN as a function of X-ray obscuration and optical classification in the Chandra Deep Field South. The sample consists of the Chandra hard--band detections with hard flux >10^-15 erg/s/cm^2. A deep 24 micron mosaic obtained with Spitzer provides mid--infrared fluxes for the sample. Since obscured AGN locally have higher 24 micron / 2-8 keV ratios than unobscured AGN, and since X-ray background models predict a large population of obscured AGN, we expect to find many X-ray--hard, IR--bright AGN. Instead, we find that the 24 micron to X-ray flux ratio does not depend on X-ray hardness in the full sample, nor does it differ between narrow--line and broad--line AGN. We identify 5 nearly Compton--thick AGN, and find they have similar 24 micron to X-ray flux ratios compared to the full sample. We consider AGN in the narrow redshift spikes at z~0.7; for these AGN, there is some evidence that the flux ratio increases with X-ray hardness. The redshift slice also shows an odd trend, which is also prominent in the full sample: a group of X-ray--hard AGN with very low 24 micron to X-ray flux ratios.

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J. R. Rigby, G. H. Rieke, R. Maiolino, R. Gilli, C. Papovich, P. G. Perez-Gonzalez, A. Alonso-Herrero, E. Le Floc'h, C. W. Engelbracht, K. Gordon, D. C. Hines, J. L. Hinz, J. E. Morrison, J. Muzerolle, M. J. Rieke, K. Y. Su. 2004-06-01. 24 micron Properties of X-ray Selected AGN. https://arxiv.org/abs/astro-ph/0406029

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