A Survey of Local Group Galaxies Currently Forming Stars: II. UBVRI Photometry of Stars in Seven Dwarfs

Philip Massey (1); K. A. G. Olsen (2); Paul W. Hodge (3); George H. Jacoby (4); Reagin T. McNeil (5); R. C. Smith (2); Shay B. Strong (6)

(1) Lowell Observatory; (2) CTIO/NOAO; (3) University of Washington; (4) WIYN Observatory; (5) Smith College; (6) University of Texas

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

Reference: Astronomical Journal, in press
Status: Manuscript has been accepted

Weblink: http://www.lowell.edu/users/massey/dwarfs.pdf.gz


Email: Phil.Massey@lowell.edu