Stellar Content and Recent Star Formation History of the Local Group Dwarf Irregular Galaxy IC1613

TL;DR

This study provides a detailed analysis of the stellar content, structure, and recent star formation history of the dwarf irregular galaxy IC1613, revealing its extended size, age gradient, and star formation rate over the last 300 million years.

Contribution

It offers the first resolved-star photometry reaching I~23.5 for IC1613 and combines structural and star formation history analysis, highlighting its extended structure and age gradient.

Findings

IC1613 has an exponential stellar density profile with a scale length of 2.9'

The galaxy is more extended than previously thought, with many RGB stars in the outer regions

Recent star formation rate is approximately 1.6 x 10^{-3} Mo/yr/kpc^2 in the last 300 Myr

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.