BALQSO Spectra Explained by Shock Disruption of Galactic Clouds

Abstract

Blue-shifted Broad Absorption Lines (BALs) detected in quasar's spectra are indicative of AGN outflows. We show, using 2D hydrodynamical simulations, that disruption of interstellar clouds by a fast AGN wind can lead to formation of cold, dense high speed blobs that give rise to broad absorption features in the transmission spectrum of the AGN continuum source. For a wind velocity of $0.1 c$ and sufficiently high cloud density ($n_{c}$ < $10^4$ cm$^{-3}$, depending on size), absorption troughs with velocities up to about $3000$ km s$^{-1}$ can be produced. For slower winds and/or lower cloud density the anticipated velocity of the absorbing clouds should be smaller.