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Session 9 - Dwarf Galaxies.
Display session, Monday, June 10
Great Hall,

[9.05] HST Photometry of the Stellar Populations in the Sextans A Dwarf Irregular Galaxy

E. D. Skillman, R. C. Dohm-Palmer (UMN), A. Saha, E. Tolstoy (STScI), C. Chiosi (Padova), R. J. Dufour (Rice), J. Gallagher, J. Hoessel (UWI), M. Mateo (UMI)

We have used the Hubble Space Telescope to observe the resolved stars of the nearby (D = 1.4 Mpc) dwarf irregular galaxy Sextans A. The data consist of WF/PC2 images in 3 bands: F439W (1 hour), F555W (30 minutes), and F814W (30 minutes). The stellar photometry was extracted using the DoPHOT program developed by Schechter, Mateo amp; Saha (1993, PASP, 105, 1342) with modifications for WF/PC2 data by Saha et al. (1996, ApJ, submitted). From this photometry, we were able to construct color-magnitude diagrams (CMD) and color-color diagrams down to a limiting magnitude of 26 in V. The CMD shows excellent detail. The main sequence, blue-loop stars, red supergiants, and red giant branch are all clearly distinct distributions in the CMDs. From these diagrams, we can constrain the star formation history of Sextans A through a statistical comparison with stellar evolution models.

Program listing for Monday