抄録
We report on a systematic investigation of the γ-ray properties of 120 hard X-ray-selected Seyfert galaxies classified as "radio-quiet" objects, utilizing the three-year accumulation of Fermi Large Area Telescope (LAT) data. Our sample of Seyfert galaxies is selected using the Swift Burst Alert Telescope 58 month catalog, restricting the analysis to the bright sources with average hard X-ray fluxes F14 - 195 keV ≥ 2.5 × 10-11erg cm-2 s-1at high Galactic latitudes (|b| > 10°). In order to remove "radio-loud" objects from the sample, we use the "hard X-ray radio loudness parameter," R rX, defined as the ratio of the total 1.4 GHz radio to 14-195 keV hard X-ray energy fluxes. Among 120 X-ray bright Seyfert galaxies with R rX <10-4, we did not find a statistically significant γ-ray excess (TS > 25) positionally coincident with any target Seyferts, with possible exceptions of ESO 323-G077 and NGC6814. The mean value of the 95% confidence level γ-ray upper limit for the integrated photon flux above 100MeV from the analyzed Seyferts is ≃ 4 × 10 -9photons cm-2 s-1, and the upper limits derived for several objects reach ≃ 1 × 10-9photons cm-2 s-1. Our results indicate that no prominent γ-ray emission component related to active galactic nucleus activity is present in the spectra of Seyferts around GeV energies. The Fermi-LAT upper limits derived for our sample probe the ratio of γ-ray to X-ray luminosities Lγ/LX < 0.1, and even <0.01 in some cases. The obtained results impose novel constraints on the models for high-energy radiation of "radio-quiet" Seyfert galaxies.
本文言語 | English |
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論文番号 | 104 |
ジャーナル | Astrophysical Journal |
巻 | 747 |
号 | 2 |
DOI | |
出版ステータス | Published - 2012 3月 10 |
ASJC Scopus subject areas
- 天文学と天体物理学
- 宇宙惑星科学