Fermi/LAT Observations of Swift/BAT Seyfert Galaxies: On the Contribution of Radio-quiet Active Galactic Nuclei to the Extragalactic γ-Ray Background
Abstract
We present the analysis of 2.1 years of Fermi Large Area Telescope (LAT) data on 491 Seyfert galaxies detected by the Swift Burst Alert Telescope (BAT) survey. Only the two nearest objects, NGC 1068 and NGC 4945, which were identified in the Fermi first year catalog, are detected. Using Swift/BAT and radio 20 cm fluxes, we define a new radio-loudness parameter R X, BAT where radio-loud objects have log R X, BAT > -4.7. Based on this parameter, only radio-loud sources are detected by Fermi/LAT. An upper limit to the flux of the undetected sources is derived to be ~2 × 10-11 photons cm-2 s-1, approximately seven times lower than the observed flux of NGC 1068. Assuming a median redshift of 0.031, this implies an upper limit to the γ-ray (1-100 GeV) luminosity of <~ 3 × 1041 erg s-1. In addition, we identified 120 new Fermi/LAT sources near the Swift/BAT Seyfert galaxies with significant Fermi/LAT detections. A majority of these objects do not have Swift/BAT counterparts, but their possible optical counterparts include blazars, flat-spectrum radio quasars, and quasars.
- Publication:
-
The Astrophysical Journal
- Pub Date:
- December 2011
- DOI:
- 10.1088/0004-637X/742/2/66
- arXiv:
- arXiv:1109.2734
- Bibcode:
- 2011ApJ...742...66T
- Keywords:
-
- galaxies: active;
- galaxies: Seyfert;
- gamma rays: diffuse background;
- X-rays: diffuse background;
- X-rays: galaxies;
- Astrophysics - High Energy Astrophysical Phenomena
- E-Print:
- 19 pages preprint style, including 2 tables and 4 figures. Accepted for publication by the Astrophysical Journal