The X-Ray Properties of 2MASS Red Active Galactic Nuclei
Abstract
The Two Micron All Sky Survey is finding previously unidentified, luminous, red, active galactic nuclei (AGNs). This new sample has a space density similar to, or greater than, previously known AGNs, suggesting that a large fraction of the overall population has been missed. Chandra observations of a well-defined subset of these objects reveal that all are X-ray-faint, with the reddest sources being the faintest in X-rays. The X-ray hardness ratios cover a wide range, generally indicating NH~1021-1023 cm-2, but the softest sources show no spectral evidence for intrinsic absorption. These characteristics suggest that a mix of absorbed, direct emission and unabsorbed, scattered, and/or extended emission contributes to the X-ray flux, although we cannot rule out the possibility that they are intrinsically X-ray-weak. This population of X-ray-faint, predominantly broad-line objects could provide the missing population of X-ray-absorbed AGNs required by current models of the cosmic X-ray background. The existence of AGNs that display both broad emission lines and absorbed X-rays has important implications for unification schemes and emphasizes the need for care in assigning classifications to individual AGNs.
- Publication:
-
The Astrophysical Journal
- Pub Date:
- January 2002
- DOI:
- arXiv:
- arXiv:astro-ph/0112433
- Bibcode:
- 2002ApJ...564L..65W
- Keywords:
-
- Galaxies: Quasars: General;
- Surveys;
- X-Rays: Galaxies;
- Astrophysics
- E-Print:
- ApJ Letters in press, 12 pages, latex, 2 figures, also available at http://hea-www.harvard.edu/~belinda/HomePage.html