The Local Group dwarf irregular galaxy IC 1613 I. The young stellar content

We obtained U-band photometry of 1500 stars and BV-band photometry of 3100 stars in a field centred on the HII regions of the northeast sector of the dwarf irregular galaxy IC 1613 - a member of the Local Group. The ages of t he stellar populations were determined from the ((B - V)(0), M-V) color-mag nitude using the isochrones from Padua's library. The stellar populations w ere split into three groups: the group of the youngest stars with ages of b etween 5 and 20 Myr, the group of intermediate stars with ages of 200 - 300 Myr and the group of old stars with ages up to 10 Gyr. The slope of the St ellar Initial Mass Function (IMF) for blue stars is Gamma = -2.0 +/- 0.1 wh ich is similar to that of other nearby galaxies. We investigated the stella r content of nine Hedge associations as well as that of seven new OB associ ations determined by cluster analysis. The total U, B and V magnitudes of e ight Hedge open clusters and two new cluster candidates are given and there are six new possible nonstellar objects-reported. The latter are most prob ably distant galaxies visible through the disk of IC 1613, which confirms t he original suggestion of Baade that IC 1613 contains no bright globular cl usters.