A Comparison of Hard X-ray Photon Indices and Iron Kα Emission Lines in X-ray Luminous Narrow- and Broad-line Seyfert 1 Galaxies

Abstract

We use publicly available XMM-Newton data to systematically compare the hard X-ray photon indices, Γ_{2-10 keV} , and the iron Kα emission lines of narrow- and broad-line Seyfert 1 (NLS1 and BLS1) galaxies. We compile a flux-limited (f _{2-10 keV} >= 1 × 10^-12 erg s^-1 cm^-2) sample including 114 radio-quiet objects, with the 2-10 keV luminosity ranging from 10⁴¹ to 10⁴⁵ erg s^-1. Our main results are: (1) NLS1s and BLS1s show similar luminosity distributions; (2) the weighted means of Γ_{2-10 keV} of NLS1s, BLS1s, and the total sample are 2.04 ± 0.04, 1.74 ± 0.02, and 1.84 ± 0.02, respectively; a significant anti-correlation between Γ_{2-10 keV} and FWHMHβ suggests that Γ_{2-10 keV} > 2.0 may be taken to indicate the X-ray luminous NLS1 type; (3) the 6.4 keV narrow iron Kα lines from NLS1s are generally weaker than that from BLS1s; this would indicate a smaller covering factor of the dusty tori in NLS1s if the line emission originates from the inner boundary region of the dusty torus in an active galactic nucleus; and (4) all the broadened iron Kα lines with intrinsic width σ>0.5 keV correspond to FWHMHβ <=4000 km s^-1.