The soft X-ray/NLR connection: a single photoionized medium?

Abstract

We present a sample of 8 nearby Seyfert 2 galaxies observed by HST and Chandra. All of the sources present soft X-ray emission which is coincident in extension and overall morphology with the [OIII] emission. The spectral analysis reveals that the soft X-ray emission of all the objects is likely to be dominated by a photoionized gas. This is strongly supported by the 190 ks combined XMM-Newton/RGS spectrum of Mrk3, which different diagnostic tools confirm as being produced in a gas in photoionization equilibrium with an important contribution from resonant scattering. We tested with the code CLOUDY a simple scenario where the same gas photoionized by the nuclear continuum produces both the soft X-ray and the [OIII] emission. Solutions satisfying the observed ratio between the two components exist, and require the density to decrease with radius roughly like $r^{-2}$, similarly to what often found for the Narrow Line Region.