A&A Supplement series, Vol. 128, March II 1998, 459-470
Received February 25; accepted July 21, 1997
L. Makarova, I. Karachentsev, L.O. Takalo, P. Heinämäki, and M. Valtonen
Send offprint request: L. Makarova
Special Astrophysical Observatory, N. Arkhyz, Stavropolsky kraj, 357147, Russia
Tuorla Observatory, Turku, Finland
In the Canes Venatici cloud, eighteen dwarf irregular galaxies were observed in bands at the Nordic Optical Telescope under a seeing of one arcsec. Most of the galaxies having radial velocities V0 < 500 km/s have been resolved into stars for the first time. The galaxy distances were derived based on photometry of their brightest blue stars. Distances to some of the galaxies: UGC 6782, UGC 7131 and, probably, K 215, which are located at the CVn southern edge, were estimated to be about 15 Mpc, which is typical of the Virgo cluster outskirts. For two LSB galaxies, K 200 and K 215, the distances may be overestimated, probably because of a lack of young massive stars. For the remaining galaxies: UGC 7559, UGC 7599, UGC 7605, UGC 7639, UGC 7698, UGCA 290, UGCA 292, UGC 7866, UGC 8024, UGC 8638, UGC 8651, UGC 8760, and UGC 8833 the estimated distances range from 2.3 to 8.0 Mpc, indicating their actual membership in the CVn cloud.
Several objects studied here (UGC 7605, UGC 7639, UGC 8638, UGC 8833) have a well-resolved bluish core and regular yellow outer parts, which may point to composite (new and old) populations. The galaxy UGCA 292 = CVn dwA has unusual global parameters: =+0.08, , and , being, perhaps, one of the youngest known objects in the Local Universe.
keywords: galaxies: distances; irregular; stellar content