Type 2 Counterparts of Narrow-Line Seyfert 1 Galaxies

Abstract

Unified models based on viewing angle successfully explain the observed differences between type 1 and type 2 Seyfert galaxies. The existence of a range in accretion rates (m˙~0.001-1) relative to the Eddington rate (from broad-line Seyfert 1's to narrow-line Seyfert 1's, or NLS1's) and the unification of Seyfert galaxies imply that there must be type 2 counterparts of NLS1's, that is, Seyfert 2's with high accretion rates or small black hole masses. One such Seyfert 2, NGC 5506, has already been unmasked based on near-infrared spectroscopy. Here we confirm the above result and present evidence for two additional type 2 counterparts of NLS1's based on XMM-Newton observations. The three active galactic nuclei NGC 7314, 7582, and 5506, with type 1.9/2 optical spectra, show extremely rapid variability, by factors of greater than 2.4, ~1.3, and ~1.7 over 200, 350, and 300 s, respectively, and steep 2-12 keV spectra (Γ>~2) in their intrinsic X-ray emission, characteristic of NLS1's. These observations establish the ``obscured NLS1 galaxies'' as a subclass of Seyfert 2 galaxies.