Are High-Velocity Clouds the Building Blocks of the Local Group?

Abstract

Motivated by the apparent order-of-magnitude discrepancy between the observed number of Local Group satellite galaxies, and that predicted by Lambda-CDM hierarchical clustering cosmologies, we explore an alternate suggestion - perhaps the missing satellites are not actually ``missing'', but are instead ``in disguise''. The disguise we consider here is that of the classical HI High-Velocity Clouds. Is it possible that what have been thought of traditionally as a ``Galactic'' phenomenon, are actually the building blocks of the Local Group? We discuss the strengths and weaknesses of this hypothesis, and highlight avenues of future research which may provide an unequivocal resolution to this contentious issue.