Clumpy stellar winds and the obscuration of active galactic nuclei

¹ Department of Physics & Astronomy, University of Leicester, Leicester, LE1 7RH, UK e-mail: sn85@astro.le.ac.uk
² Max-Planck-Institut für Astrophysik, Karl-Schwarzschild-Str.1, 85741 Garching, Germany
³ JILA, University of Colorado, 440 UCB, Boulder, CO 80309-0440, USA

Received: 4 May 2006
Accepted: 15 December 2006

Abstract

The role of star-formation driven outflows in the obscuration of the central source in Active Galactic Nuclei (AGN) is discussed. The outflow from a sub-parsec scale accretion disc is numerically modelled for parameters appropriate to the Galactic Centre. The resulting obscuration pattern is very patchy, with some lines of sight becoming optically thick to Thomson scattering. A fixed observer would see column depth changing by factors of many over time scales ranging from months to hundreds of years, depending on the physical size of the outflow region. Such winds may be relevant for the obscuration of some AGN, especially “changing look AGN”. The winds are Thomson-thick for outflow rates exceeding the Eddington accretion rate limit, which may be satisfied in strong near-AGN starbursts as observed in a few nearby galactic nuclei.