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American Astronomical Society, Astronomical Journal, 3(134), p. 1124-1132, 2007

DOI: 10.1086/520805

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Stellar Content and Recent Star Formation History of the Local Group Dwarf Irregular Galaxy IC 1613

This paper is made freely available by the publisher.
This paper is made freely available by the publisher.

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Data provided by SHERPA/RoMEO

Abstract

We present resolved-star VI photometry of the Local Group dwarf irregular galaxy IC1613 reaching I~23.5, obtained with the wide-field camera at the 2.5m Isaac Newton Telescope. A fit to the stellar density distribution shows an exponential profile of scale length 2.9' +/- 0.1 and gives a central surface brightness mu_V,0 = 22.7 +/- 0.6. The significant number of red giant branch (RGB) stars present in the outer part of our images (r > 16.5') indicates that the galaxy is actually more extended than previously estimated. A comparison of the color-magnitude diagrams (CMDs) as a function of galactocentric distance shows a clear gradient in the age of its population, the scale length increasing with age, while we find no evidence of a metallicity gradient from the width of the RGB. We present quantitative results of the recent star formation history from a synthetic CMD analysis using IAC-STAR. We find a mean star formation rate of (1.6 +/- 0.8) x 10^{-3} Mo/yr/kpc^2 in the central r < 2.5' for the last 300 Myr. Comment: 9 pages, 12 figures. Accepted for publication in AJ