Abstract
We present Hubble Space Telescope/Wide Field Planetary Camera 2 single-star photometry for the blue dwarf galaxy UGCA 290, whose morphology is intermediate between classic iE blue compact dwarf galaxies and blue dwarf galaxies that exhibit no red background sheet of older stars. The color-magnitude diagram of this galaxy in V and I, extending over 6 mag, is remarkably similar to that of the star-forming region in the iE blue compact dwarf galaxy VII Zw 403. There is no evidence for gaps in its star formation history over the last billion years, and the color of its red giant branch indicates a very metal-poor stellar population. From the magnitude of the tip of the red giant branch, we derive a distance of 6.7 Mpc, more than twice the distance estimated from the brightest blue supergiants.
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Footnotes
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Based on observations made with the NASA/ESA Hubble Space Telescope, obtained at the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS5-26555.