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X-ray spectral survey with XMM–Newton of a complete sample of nearby Seyfert galaxies
- Source :
- Astronomy and Astrophysics; February 2006, Vol. 446 Issue: 2 p459-470, 12p
- Publication Year :
- 2006
-
Abstract
- Results obtained from an X-ray spectral survey of nearby Seyfert galaxies using XMM–Newtonare reported. The sample was optically selected, well defined, complete in Bmagnitude, and distance limited: it consists of the nearest ($D \la22$Mpc) 27 Seyfert galaxies (9 of type 1, 18 of type 2) taken from the Ho et al. (1997a, ApJS, 112, 315) sample. This is one of the largest atlases of hard X-ray spectra of low-luminosity active galaxies ever assembled. All nuclear sources except two Seyfert 2s are detected between 2 and 10 keV, half for the first time ever, and average spectra are obtained for all of them. Nuclear luminosities reach values down to 1038erg s-1. The shape of the distribution of X-ray parameters is affected by the presence of Compton-thick objects ($\ga$30% among type 2s). The latter have been identified either directly from their intense FeK line and flat X-ray spectra, or indirectly with flux diagnostic diagrams which use isotropic indicators. After taking into account these highly absorbed sources, we find that (i) the intrinsic X-ray spectral properties (i.e., spectral shapes and luminosities above 2 keV) are consistent between type 1 and type 2 Seyferts, as expected from “unified models”; (ii) Seyfert galaxies as a whole are distributed fairly continuously over the entire range of NH, between 1020and 1025cm-2; and (iii) while Seyfert 1s tend to have lower NHand Seyfert 2s tend to have the highest, we find 30% and 10% exceptions, respectively. Overall the sample is of sufficient quality to well represent the average intrinsic X-ray spectral properties of nearby active galactic nuclei, including a proper estimate of the distribution of their absorbing columns. Finally, we conclude that, with the exception of a few cases, the present study agrees with predictions of unified models of Seyfert galaxies, and extends their validity down to very low luminosities.
Details
- Language :
- English
- ISSN :
- 00046361 and 14320746
- Volume :
- 446
- Issue :
- 2
- Database :
- Supplemental Index
- Journal :
- Astronomy and Astrophysics
- Publication Type :
- Periodical
- Accession number :
- ejs53177427
- Full Text :
- https://doi.org/10.1051/0004-6361:20053893