The Local Group Dwarf Galaxy Hunt

We present the results of an all-sky, deep optical survey for faint Local Group dwarf galaxies. Candidate objects were selected from the second Palomar survey (POSS-II) and ESO/SRC survey plates and follow-up observations performed to determine whether they were indeed overlooked members of the Local Group. Based on internal and external comparisons, we estimate that our visual survey is more than 77% complete (possibly as high as 90%) for objects larger than one arc minute in size and brighter than a limit of about 26 magnitudes per square arc second, over the 72% of the sky not obstructed by the Milky Way. Taking into account other searches, we conclude that there are at most one or two Local Group dwarf galaxies fitting our observational criteria still undiscovered in the clear part of the sky, and roughly a dozen hidden behind the Milky Way. Our work places the ``missing satellite problem'' on a firm quantitative observational basis.

This work was supported in part by the Intitute of Astronomy of the University of Cambridge, the Physics Department of the U. S. Naval Academy, the European Southern Observatory, and two American Astronomical Society Small Research Grants (which last funds originated with NASA). G. K. T. H. asknowledges financial support from the Chilean FONDECYT grant 1990442.