A Detection Of An X-ray Wind And An Ionized Disk In The Chandra HETGS Observation Of The Seyfert 2 Galaxy IRAS 18325-5926

Abstract

We analyze the Chandra High Energy Transmission Grating Spectrometer observation of the Seyfert 2 AGN IRAS 18325-5926. We detect a v = –360[superscript +41] [subscript –66] km s[superscript –1] blueshifted ionized absorber in the X-ray spectrum, with photoionization parameter log ξ = 2.0[superscript +0.1] [subscript –0.1] and hydrogen column density N H = 1.55[superscript +0.75] [subscript –0.38] × 10[superscript 21] cm[superscript –2]. The absorber may be a photoionized wind originating in the obscuring torus/global covering around the black hole or outer edge of the accretion disk. The estimated mass outflow rate suggests that the supermassive black hole in IRAS 18325-5926 may significantly affect the large-scale environment of the host galaxy, unless the solid angle subtended by the outflow or the gas filling factor is small. A second warm absorber may be needed to explain the absorption features in the vicinity of the iron K edge, although insufficient counts in the data beyond 7.0 keV make it difficult to assess the nature of the second absorber. Most plausible is a high ionization (log ξ ~ 2.3 to 2.6), high column density (N H ~ 1023 cm–2) absorber with v ~ –3000 to 0 km s–1, although these parameters are not well constrained. We also examine the broad Fe K emission line in the spectrum, which is likely due to Fe XXV in a highly ionized accretion disk inclined at 25°, consistent with the XMM-Newton EPIC observations of the emission line. Because we are able to view both the obscuring gas and the accretion disk of IRAS 18325-5926, the surrounding gas of IRAS 18325-5926 may be patchy or we are viewing the system at an angle just grazing the obscuring torus.