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, Γ2-10 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 Γ2-10 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 Γ2-10 keV and FWHMHβ suggests that Γ2-10 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.