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

[9.03] The Tucana Dwarf Galaxy: HST/WFPC2 Imaging of this Isolated Local Group Dwarf Spheroidal

R. J. Lavery (Iowa State), P. Seitzer (Michigan), A. R. Walker, N. B. Suntzeff (CTIO/NOAO), G. S. D. Costa (MSO)

HST/WFPC2 images in the F555W and F814W filters have been obtained of the Tucana Dwarf Galaxy, an isolated dwarf spheroidal member of the Local Group of Galaxies. Our color-magnitude diagram reaches two magnitudes below the horizontal branch. Assuming an M(V) of +0.6 for the absolute magnitude for the RR Lyrae stars, we find a distance modulus of (m-M) = 24.7 +/- 0.1. The CM diagram shows no young blue stars, suggesting the Tucana dwarf has been quiescent for a relatively long period since its last star formation episode. Additional details on the star formation history and the metallicity of this intriguing galaxy, determined from the morphology of the horizontal branch, the giant branch, the RR Lyrae stars and the presence of several possible carbon stars, will be presented.

Program listing for Monday