BALQSO spectra explained by shock disruption of galactic clouds

Blue-shifted broad absorption lines (BALs) detected in quasar’s spectra are indicative of active galactic nuclei (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 0.1c and sufficiently high cloud density (n_c 10⁴ cm⁻³; depending on size), absorption troughs with velocities up to about 3000 km s⁻¹can be produced. For slower winds and/or lower cloud density, the anticipated velocity of the absorbing clouds should be smaller.