Chemical abundances in AGN : X-ray/UV campaign on Mrk 279 .

Abstract

We present the first reliable chemical abundances determination in an AGN outflow. The abundances are extracted from the deep and simultaneous FUSE and HST/STIS observations of Mrk 279. This data-set is exceptional for it's high signal-to-noise, unblended doublet troughs and little galactic absorption contamination. These attributes allow us to solve for the velocity dependent covering fraction, and therefore obtain reliable column density for many ionic species. For the first time we have enough such column densities to simultaneously determine the ionization equilibrium and abundances in the flow. Our analysis use the full spectral information embedded in these high-resolution data. Slicing a given trough to many independent outflow elements yields the extra constraints needed for a physically meaningful abundances determination. We find that relative to solar the abundances in the Mrk 279 outflow are: carbon 2.2±0.7, nitrogen 3.5±1.1 and oxygen 1.6±0.8.