Momentum transfer by an internal source of ionizing radiation: an important feedback process during galaxy formation?

The role of momentum transfer (``radiation pressure'') due to an internalsource of ionizing radiation for the formation of baryonic structures isinvestigated. Fully-ionized self-gravitating gaseous objects can beradiation-pressure supported on a characteristic length scale $D_{\rm rp} \sim100 \pc - 3 \kpc$. On smaller scales momentum transfer due to ionizingradiation will be the dominant force and for spherical collapsing objects ofmass $\la 10^{10}\Msol$ a complete bounce is possible. A population of massivestars and/or accretion onto a central compact object are natural sources ofionizing radiation in newly-forming baryonic structures. Radiation pressure istherefore likely to play an important role for the dynamical and thermalevolution of the intergalactic medium and the mass-to-light ratio of smallgalaxies. The effect will be especially important for hierarchical cosmogonieswhere galactic structures build up by merging of smaller objects. Radiationpressure due to ionizing radiation might furthermore be responsible forsubstructures of size $D_{\rm rp}$ in the stellar component of large galaxies.Comment: 18 pages (incl. 2 figures), uuencoded compressed postscript file (uufiles), MPA-83