  Reionization is thought to be dominated by low mass galaxies, while direct
observations of resolved galaxies probe only the most massive, rarest objects.
The cross-correlation between fluctuations in the surface brightness of the
cumulative Ly-alpha emission (which serves as a proxy for the star formation
rate) and the redshifted 21cm signal from neutral hydrogen in the intergalactic
medium (IGM), will directly probe the causal link between the production of
ionizing photons in galaxies and the reionization of the IGM. We discuss the
prospects for detecting this cross-correlation for unresolved galaxies. We find
that on angular scales <10 arc-minutes, detection will be practical using
widefield near-IR imaging from space in combination with the forthcoming
Mileura Widefield Array - Low Frequency Demonstrator. When redshifted 21cm
observations of the neutral IGM are combined with space-based near-IR imaging
of Ly-alpha emission, the detection on angular scales <3 arc-minutes will be
limited by the sensitivity of the 21cm signal, even when a small aperture
optical telescope (~2m) and a moderate field of view (~10 square degrees) are
used. On scales >3 arc-minutes, the measurement of cross-correlation will be
limited by the accuracy of the foreground sky subtraction.
