Unveiling a population of agns not detected in x-rays

J. L. Donley, G. H. Rieke, J. R. Rigby, P. G. Pérez-González

Research output: Contribution to journalArticlepeer-review

110 Scopus citations


We define a sample of 27 radio-excess AGNs in the Chandra Deep Field-North by selecting galaxies that do not obey the radio/infrared correlation for radio-quiet AGNs and star-forming galaxies. Approximately 60% of these radio-excess AGNs are undetected in X-rays in the 2 Ms Chandra catalog, even at exposures of ≥1 Ms; 25% lack even 2 σ X-ray detections. The absorbing columns to the faint objects detected in X-rays are 1022 cm -2 < NH < 1024 cm-2; i.e., they are obscured but unlikely to be Compton-thick. Using a local sample of radio-selected AGNs, we show that a low ratio of X-ray to radio emission, as seen in the samples of AGNs weakly detected and undetected in X-rays, is correlated with the viewing angle of the central engine and therefore with obscuration. Our technique can explore the proportion of obscured AGNs in the distant universe; the results reported here for radio-excess objects are consistent with, but at the low end of, the overall theoretical predictions for Compton-thick objects.

Original languageEnglish (US)
Pages (from-to)169-182
Number of pages14
JournalAstrophysical Journal
Issue number1 I
StatePublished - Nov 20 2005


  • Galaxies: active
  • Radio continuum: galaxies
  • X-rays: galaxies

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science


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