SIMBAD references

We obtained HST/WFPC2 images of the dwarf spheroidal (dSph) galaxies K 61, K 63, K 64, DDO 78, BK 6N, and kk 77 in the M 81 group. Our color-magnitude diagrams show red giant branches with tips (TRGB) falling within the range of I=[23.8-24.0]mag. The derived true distance moduli (DM) of the 6 dSphs ranging from 27.71 to 27.93mag are consistent with their membership in the group. Given accurate distances of 5 other group members, which have been derived via TRGB or cepheids, the mean DM of the M81 group is (27.84±0.05) mag. We find the difference of the mean distances to the M81 and NGC 2403 groups to be D_M81-D_NGC2403=(0.5±0.2)Mpc, which yields a deprojected separation of 0.9Mpc. With respect to the Local group, M 81 and NGC 2403 have radial velocities of 106 and 267km/s respectively, while the velocities of the group centroids are 142 and 281km/s. The higher velocity of the closer system may indicate that these groups are moving towards each other, similar to the Milky Way and M 31 in the Local group. Several globular cluster candidates have been identified in the galaxies.