Discovery of New Dwarf Galaxies in the M81 Group

An order of magnitude more dwarf galaxies are expected to inhabit the Local Group, based on currently accepted galaxy formation models, than have been observed. This discrepancy has been noted in environments ranging from the field to rich clusters. However, no complete census of dwarf galaxies exists in any environment. The discovery of the smallest and faintest dwarfs is hampered by the limitations in detecting such faint and low surface brightness galaxies. An even greater difficulty is establishing distances to, or group/cluster membership for, such faint galaxies. The M81 Group provides an almost unique opportunity for establishing membership for galaxies in a low-density region complete to magnitudes as faint as . With a distance modulus of 27.8, the tip of the red giant branch just resolves in ground-based surveys. We have surveyed a 65 deg 2 region around M81 with Canada-France-Hawaii Telescope/MegaCam. From these images, we have detected 22 new dwarf galaxy candidates. Photometric, morphological, and structural properties are presented for the candidates. The group luminosity function has a faint-end slope characterized by the parameter α = −1.27 ± 0.06. We discuss implications of this dwarf galaxy population for cosmological models.