Unable to contact STScI submission server Assigned ID: 290 ----- Submission 1 (Fri Jan 21 18:51:19 GMT 2005) ----- Program can be submitted with the evidenced warning Surface Brightness Fluctuations (SBF) provide a highly promising tool for tracing the properties of unresolved stellar populations in external galaxies. We propose to measure radial SBF gradients in archival ACS/F814W images of early-type galaxies and correlate these gradients with their broadband colors. As we have demonstrated in preliminary investigations, the exceptional imaging capabilities of ACS now makes it possible to measure highly accurate SBF gradients in a large sample of galaxies. Comparison of our preliminary results with new stellar population models shows that SBF, and SBF gradients with radius, complement the information provided by classical photometry, helping to break the usual age/metallicity degeneracy. The proposed archival research would more than double the number of galaxies with measured SBF gradients, including the addition of shell galaxies, which likely have had interesting and complex star formation histories. In addition, we will measure near-IR SBF properties in a subsample of these galaxies that also have NICMOS imaging, providing substantially more leverage for breaking the age/metallicity degeneracy.

GALAXIES 12 98000 false 0.0 false false false false false SUPPORTED