24 Micron Properties of X-Ray-selected Active Galactic Nuclei Academic Article uri icon


  • We examine the 24 m to X-ray color of 157 X-ray-selected active galactic nuclei (AGNs) 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 2-8 keV flux above 10 -15 ergs s -1 cm -2 . A deep 24 m mosaic obtained with Spitzer provides mid-infrared fluxes for the sample. Since obscured AGNs locally have higher 24 m/2-8 keV flux ratios than unobscured AGNs, and since X-ray background models predict a large population of obscured AGNs, we expect to find many X-ray-hard, IR-bright AGNs. Instead, we find that the 24 m to X-ray flux ratio does not depend on X-ray hardness in the full sample, nor does it differ between narrow- and broad-line AGNs. We identify five nearly Compton-thick AGNs and find they have similar 24 m to X-ray flux ratios compared to the full sample. We consider AGNs in the narrow redshift spikes at z 0.7; for these AGNs, there is some evidence that the flux ratio increases with X-ray hardness. The redshift slice also shows an odd trend that is also prominent in the full sample: a group of X-ray-hard AGNs with very low 24 m to X-ray flux ratios.

published proceedings

  • The Astrophysical Journal Supplement Series

author list (cited authors)

  • Rigby, J. R., Rieke, G. H., Maiolino, R., Gilli, R., Papovich, C., Prez-Gonzlez, P. G., ... Su, K.

citation count

  • 38

complete list of authors

  • Rigby, JR||Rieke, GH||Maiolino, R||Gilli, R||Papovich, C||Pérez-González, PG||Alonso-Herrero, A||Le Floc’h, E||Engelbracht, CW||Gordon, K||Hines, DC||Hinz, JL||Morrison, JE||Muzerolle, J||Rieke, MJ||Su, KYL

publication date

  • September 2004