A Search for Stellar Obscuration Events Due to Dark Clouds

The recent detections of a large population of faint submillimetre sources,an excess halo gamma-ray background, and the extreme scattering events observedfor extragalactic radio sources have been explained as being due to baryonicdark matter in the form of small, dark, gas clouds. In this paper we presentthe results of a search for the transient stellar obscurations such clouds areexpected to cause. We examine the Macho project light curves of 48 x 10^6 starstoward the Galactic bulge, LMC and SMC for the presence of dark cloudextinction events. We find no evidence for the existence of a population ofdark gas clouds with Av > 0.2 and masses between ~ 10^-4 and 10^-2 M_solar inthe Galactic disk or halo. However, it is possible that such dark cloudpopulations could exist if they are clustered in regions away from the observedlines of sight.Comment: 13 pages, 9 figures, submitted to Ap