A Survey of Local Group Galaxies Currently Forming Stars: II. UBVRI Photometry of Stars in Seven Dwarfs and a Comparison of the Entire Sample

摘要

We have obtained UBVRI images with the Kitt Peak and Cerro Tololo 4-mtelescopes and Mosaic cameras of seven dwarfs in (or near) the Local Group, allof which have known evidence of recent star formation: IC10, NGC 6822, WLM,Sextans B, Sextans A, Pegasus,and Phoenix. We construct color-magnitudediagrams (CMDs) of these systems, as well as neighboring regions that can beused to evaluate the degree of foreground contamination by stars in the MilkyWay. Inter-comparison of these CMDs with those of M31, M33, the LMC, and theSMC permits us to determine improved reddening values for a typical OB starfound within these galaxies. All of the CMDs reveal a strong or modest numberof blue supergiants. All but Pegasus and Phoenix also show the clear presenceof red supergiants in the CMD, although IC10 appears to be deficient in theseobjects given its large WR population. The bright stars of intermediate colorin the CMD are badly contaminated by foreground stars (30-100%), andconsiderable spectroscopy is needed before statistics on the yellow supergiantsin these systems will be known. This study is intended to serve both as theimpetus and "finding charts" for further space-based imaging, and for manyspectroscopic programs at large aperture.