Soft X-ray Spectroscopy of Seyfert 2 Galaxies

Soft X-ray spectroscopy of Seyfert 2 galaxies offers perhaps the best method to probe the possible connection between AGN activity and star formation. Obscuration of powerful radiation from the inferred nucleus allows for detailed study of circumnuclear emission regions. And soft X-ray spectroscopy of these regions allows for robust discrimination between warm gas radiatively driven by the AGN and hot collisionally-driven gas possibly associated with star formation. A simple model of a (bi-)cone of gas photoionized and photoexcited by a nuclear power-law continuum is sufficient to explain the soft X-ray spectra of all Seyfert 2 galaxies so far observed by the XMM-Newton and Chandra satellites. An upper limit of around 10 percent to an additional hot, collisionally-driven gas contribution to the soft X-ray regime appears to hold for five different Seyfert 2 galaxies, placing interesting constraints on circumnuclear star formation.