The M101 Group

The M101 group of galaxies is a 'poor' group, in contrast to the 'rich' M81 group. The main galaxy is M101, a Sc galaxy at approx. 6.5 to 7Mpc and total magnitude of 22#22 in 10#10. There are only twelve members or possible members, and these are all of the late types Sm or Im, except for one nucleated dwarf elliptical. There is a notable lack of faint dwarfs in the group, the faintest possible member having a magnitude of 23#23 in 10#10. This lack of faint dwarfs is apparent when comparing with the M81 group, which has members as faint as 24#24 in 10#10. We⁶ unsuccessfully visually searched the region on POSSII plates for possible member candidates. One candidate BCD was found, but photometry of the galaxy was impossible due to a projected close bright star. Also, no velocity is known for this galaxy. Blind HI searches have not revealed any new candidate yet. The larger distance to the group could render detections of very faint galaxies difficult though, so more sensitive instruments could reveal fainter group members in the future. A map of the M101 group as currently known is shown in Fig. .

Figure: Sky map (conical equidistant projection) of the M101 group and surrounding field. The galaxies are coded according to group membership and types. Group members and possible members are indicated by triangles and inverted triangles, respectively, field galaxies by squares. Early types are represented by filled symbols and late types by open ones. M101 is plotted as a large cross. The galaxies M51 and M63 are shown with smaller crosses.

25#25

I imaged a total of 21 galaxies during an eight night run in March 1997 at the OHP. Eleven of the imaged galaxies are members and suspected members of the group and ten are field galaxies.