The Star Formation History of the Carina Dwarf Spheroidal Galaxy

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Session 39 -- Spiral, Dwarf and Irregular Galaxies
Display presentation, Wednesday, June 14, 1995, 9:20am - 6:30pm

[39.02] The Star Formation History of the Carina Dwarf Spheroidal Galaxy

Denise Hurley-Keller, Mario Mateo (Univ. of Michigan), James Nemec (Dominion Astrophysical Observatory)

Previous results suggest that the Carina dwarf galaxy has a complex star formation history, possibly involving two distinct bursts of activity (Smecker-Hane et al. AJ, 180, 507 (1994); Mighell A\&AS, 82, 1 (1990)). We have obtained deep CCD photometry (limiting magnitude $V \sim 24.5$) of three fields in the Carina dwarf galaxy, reaching well below the main-sequence turnoff in each field. We present the results of a detailed study of the turnoff region using a program we have developed which allows us to model various star formation scenarios. The program creates synthetic photometry for stars which it has randomly generated according to a mass function, age and metallicity distributions. Photometric errors are assigned to the stars based on the error distributions of the data. The resulting color-magnitude diagram is corrected for completeness as determined by a false star analysis of the images. By quantitatively comparing the synthetic results with the data, we can evaluate the feasibility of various star formation scenarios. By comparing the photometry in the three fields, we hope to determine whether there are any significant spatial variations in the star formation history of the galaxy. In addition, for two of the Carina fields, the data were obtained to allow us to identify short-period variable stars such as RR~Lyr stars and SX~Phe stars. We report on the frequency of these objects and discuss the astrophysical implications we derive from them.

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