EDP Sciences
Free access
Volume 414, Number 2, February I 2004
Page(s) 399 - 408
Section Cosmology
DOI http://dx.doi.org/10.1051/0004-6361:20034134

A&A 414, 399-408 (2004)
DOI: 10.1051/0004-6361:20034134

Mass-loaded spherical accretion flows

J. M. Pittard1, T. W. Hartquist1, I. Ashmore1, A. Byfield1, J. E. Dyson1 and S. A. E. G. Falle2

1  School of Physics and Astronomy, The University of Leeds, Woodhouse Lane, Leeds, LS2 9JT, UK
2  Department of Applied Mathematics, The University of Leeds, Woodhouse Lane, Leeds, LS2 9JT, UK

(Received 29 July 2003 / Accepted 17 October 2003 )

We have calculated the evolution of spherical accretion flows undergoing mass-loading from embedded clouds through either conduction or hydrodynamical ablation. We have observed the effect of varying the ratios of the mass-loading timescale and the cooling timescale to the ballistic crossing timescale through the mass-loading region. We have also varied the ratio of the potential energy of a particle injected into the flow near the outer region of mass-loading to the temperature at which a minimum occurs in the cooling curve. The two types of mass-loading produce qualitatively different types of behaviour in the accretion flow, since mass-loading through conduction requires the ambient gas to be hot, whereas mass ablation from clumps occurs throughout the flow. Higher ratios of injected to accreted mass typically occur with hydrodynamical ablation, in agreement with previous work on wind-blown bubbles and supernova remnants. We find that mass-loading damps the radiative overstability of such flows, in agreement with our earlier work. If the mass-loading is high enough it can stabilize the accretion shock at a constant radius, yielding an almost isothermal subsonic post-shock flow. Such solutions may be relevant to cooling flows onto massive galaxies. Mass-loading can also lead to the formation of isolated shells of high temperature material, separated by gas at cooler temperatures.

Key words: accretion, accretion disks -- shock waves -- instabilities -- ISM: kinematics and dynamics -- galaxies: cooling flows

Offprint request: J. M. Pittard, jmp@ast.leeds.ac.uk

© ESO 2004