High-Resolution X-Ray Spectroscopy of the Seyfert 2 Galaxy Circinus with [ITAL]Chandra[/ITAL]

Results from a 60 ks Chandra HETGS observation of the nearby Seyfert 2Circinus are presented. The spectrum shows a wealth of emission lines at bothsoft and hard X-rays, including lines of Ne, Mg, Si, S, Ar, Ca, and Fe, and aprominent Fe Kalpha line at 6.4 keV. We identify several of the He-likecomponents and measure several of the Lyman lines of the H-like ions. Thelines' profiles are unresolved at the limited signal-to-noise ratio of thedata. Our analysis of the zeroth-order image in a companion paper constrainsthe size of the emission region to be 20-60 pc, suggesting that emission withinthis volume is almost entirely due to the reprocessing of the obscured centralsource. Here we show that a model containing two distinct components canreproduce almost all the observed properties of this gas. The ionized componentcan explain the observed intensities of the ionized species, assumingtwice-solar composition and an N \propto r^{-1.5} density distribution. Theneutral component is highly concentrated, well within the 0.8arcsec pointsource, and is responsible for almost all of the observed Kalpha (6.4 keV)emission. Circinus seems to be different than Mkn~3 in terms of its gasdistribution.Comment: Figure 1 in color. ApJ Letters, in pres