Stellar populations in the local group starburst galaxy IC10

The galaxies of the Local Group (LG) are located within 1 Mpc and they can be resolved into stars. These systems are important laboratories both to provide firm constraints on cosmological parameter, like the dark matter, and to investigate galaxy formation and stellar evolution. In particular, the study of the gas rich dwarf Irregular (dIrr) galaxies allows us to investigate the formation of stars in a different environment. In this contest, IC10 is a very interesting object. In fact, it is a dIrr and it is the only starburst galaxy of the LG. Both reddening and distance estimates for this galaxy are uncertain, due to its position and the extension of IC10 is not well known. This PhD project is focused on a photometric study of this galaxy. I have combined accurate and deep optical data collected with the Advanced Camera for Surveys and with the Wide Field Planetary Camera 2 on board the Hubble Space Telescope. Moreover, I have used accurate and deep optical data collected with the Suprime-Cam of the Subaru Telescope and with the MegaCam of the Canada France Hawaii Telescope. The high resolution of space data combined with the wide field of the ground-based data allowed me to determine distance and reddening of this object. I have found a true distance modulus of µ = 24.60±0.15 mag. Moreover, I have found evidence of differential reddening (E(B − V ) = 0.78 ± 0.06 mag in the burst region and E(B−V ) = 0.63±0.09 mag in the no-burst region). I have investigated the stellar content of IC10. There is evidence of age and metallicity spread. The study of the Helium burning regions displayed the presence of both old and intermediate-age stars. Star counts across both the starburst and the nostarburst regions suggest the occurrence of IC10 stars within 40 arcminutes. This evidence suggests that IC10 is six time more extent than what thought. From the selection of the stars of IC10 I have determined the luminosity within a diameter of 13arcminutes (LV = 5.88x107L) and a mass-to-luminosity ratio of M/L ∼ 10.5M/L. It is a factor of seven larger than the previous values. This suggests that IC10 is a dark matter dominated syste.