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Session 68 - Disk Galaxies.
Display session, Wednesday, January 15
Metropolitan Ballroom,
The density wave theory of the spiral structure of galaxies makes definitive predictions about the differences in age of the stellar populations inside an arm as compared to the stars in front of and behind the arm. To test these predictions, we have examined archival HST WFPC2 images of the Virgo Sc galaxy NGC4321 (M100). We compare the stellar population across the spiral arms using color-magnitude diagrams for the resolved stars and integrated surface brightnesses and colors for the unresolved stars. Images with artificial stars added are used to estimate the completeness in the number of resolved stars as a function of magnitude and color. We find conspicuous age differences for both the northern and southern arm profiles.
