NOAO >   Observing Info >   Approved Programs >   2002B-0305

Small NOAO Logo

Proposal Information for 2002B-0305


PI: Andrew Dolphin, NOAO, dolphin@noao.edu
Address: PO Box 26732, Tucson, AZ 85732, USA

CoI: Abi Saha, NOAO

Title: Dwarf Galaxy Histories: Breaking the Age-Metallicity Degeneracy

Abstract: The age-metallicity degeneracy prevents the accurate determination of the early star formation histories of all but the nearest galaxies because the position of the red giant branch in a color-magnitude diagram is a function of both parameters (age and metallicity). This question is especially interesting because deep CMDs of many dwarf irregulars show very narrow red giant branches while also showing evidence of star formation from the most ancient ages until the present. No extremely plausible solution to this dilemma exists; the most likely is that the chemical enrichment histories of these systems, by coincidence, have the slope necessary to keep the RGB position constant. We can directly test this hypothesis by obtaining photometry of giants using the metallicity-sensitive Washington filter system. The photometry will allow us to measure both metallicity (Delta) ( M - T_1 ) and temperature ( T_1 - T_2 ) indices, which will allow the measurement of both age and metallicity for each giant photometered.


National Optical Astronomy Observatory, 950 North Cherry Avenue, P.O. Box 26732, Tucson, Arizona 85726, Phone: (520) 318-8000, Fax: (520) 318-8360



NOAO >   Observing Info >   Approved Programs >   2002B-0305

noaoprop-help@noao.edu

Small NOAO Logo