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Session 22 -- Galaxy Structure and Kinematics

Oral presentation, Monday, 30, 1994, 2:00-3:30

[22.06] Color-Magnitude Diagrams of the Brightest Stars in the Virgo Galaxy M100: Early Release Observations from HST

We present color-magnitude diagrams reaching five magnitudes down into the luminosity function for $\sim$ 10,000 of the brightest stars in the Virgo galaxy M100. These data were derived from BVR WFPC-2 images obtained as part of the Early Release Observations made by the Hubble Space Telescope shortly after the repair mission in Dec. 1993. The V luminosity function for the blue plume is found to have a slope of 0.67 consistent with Local Group studies. Many of the very brightest objects (first appearing at V = 20.5 mag) are clearly identified as complex multiple systems, association cores, and/or young clusters mostly residing in and along the high-density spiral arms. Cepheid candidates have been identified based on their apparent magnitude and color. Deeper VI exposures of less crowded adjacent fields in M100, taken as part of the HST Key Project on the Extragalactic Distance Scale, will also be presented and discussed.

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