24 micron Properties of X-ray Selected AGN
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.
Keywords
Cite
@article{arxiv.astro-ph/0406029,
title = {24 micron Properties of X-ray Selected AGN},
author = {J. R. Rigby and G. H. Rieke and R. Maiolino and R. Gilli and C. Papovich and P. G. Perez-Gonzalez and A. Alonso-Herrero and E. Le Floc'h and C. W. Engelbracht and K. Gordon and D. C. Hines and J. L. Hinz and J. E. Morrison and J. Muzerolle and M. J. Rieke and K. Y. Su},
journal= {arXiv preprint arXiv:astro-ph/0406029},
year = {2007}
}
Comments
9 pages, 5 figures; accepted to ApJS Spitzer Special Edition