The X-ray properties of 2mass red active galactic nuclei

Belinda J. Wilkes, Gary D. Schmidt, Roc M. Cutri, Himel Ghosh, Dean C. Hines, Brant Nelson, Paul S. Smith

Research output: Contribution to journalArticlepeer-review

82 Scopus citations

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 ∼ 1021-10 23 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.

Original languageEnglish (US)
Pages (from-to)L65-L68
JournalAstrophysical Journal
Volume564
Issue number2 II
DOIs
StatePublished - Jan 10 2002

Keywords

  • Quasars: general
  • Surveys
  • X-rays: galaxies

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science

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