Data acquisition & reduction

The observations are part of a long-term '10Mpc project', whose goal is to obtain detailed photometric information in at least two photometric passbands (10#10 and 11#11 in this case) of all known dwarf galaxies within 10Mpc of the Local Group (LG). The number of galaxies within this distance is not known with precision, due to the often very low surface brightness of such galaxies, but their total number is estimated to be approx. 300. Most of the known galaxies within this 10Mpc volume are concentrated in groups. These are, in the northern hemisphere, the M81 and M101 groups, the Canes Venatici I cloud (CVnI), and the Maffei/IC342 group. The latter is situated at low galactic latitude, so observation of its members are severely hampered by obscuration. The location of these groups can be appreciated in Figs. -a and -b.

Figure: (a) Sky distribution, in supergalactic coordinates, of all galaxies known within a distance of 10 Mpc. Approximate boundaries of the main groups in this volume, as well as the position of the Virgo Cluster are indicated. The galactic zone of avoidance (13#13 1514#14) is delineated with a heavy line. Large dots: giant galaxies ( 15#15), small dots: dwarf galaxies ( 16#16). (b) Spatial distribution, projected onto the supergalactic plane, of all galaxies lying closer than 10 Mpc. The Milky Way Galaxy is at the center, with the zone of avoidance as indicated by the double sector (13#13 1514#14). The orientation is also given by the direction to the Virgo Cluster. Approximate boundaries of the main groups and clouds, including the Local Group, are indicated. Large and small dots as in (a). This plot should not be taken as a true map, but rather as a schematic, as most distances used here are rough estimates only.

12#12

The galaxies in our sample were observed in four 'runs', where a specific group was usually targeted each time, except for the two first runs where only M81 group galaxies were imaged. The targets were the regions in and around the M81 Group, M101 Group and the CVnI cloud respectively. The observations were done at the Observatoire de Haute Provence (OHP) using the 1.2m telescope, with either a 17#17 pixel camera (M81) or a 18#18 pixel camera (M101 and CVnI).