Initial mass function in the South-Western part of M 31

¹ Department of Astronomy, University of Sofia, 5 James Bourchier, Sofia 1164, Bulgaria e-mail: [eirene;japet]@phys.uni-sofia.bg
² Isaac Newton Institute of Chile, Bulgarian Branch, 5 James Bourchier, Sofia 1164, Bulgaria
³ Institute of Astronomy, Bulgarian Academy of Sciences, 72 Tsarigradsko Chaussee, Sofia 1786, Bulgaria e-mail: gborisov@libra.astro.bas.bg

Received: 9 March 2004
Accepted: 7 July 2004

Abstract

We derive an average initial mass function (IMF) for 50 OB associations in the South-Western part of Andromeda galaxy, combining ultraviolet photometry of Hill et al. ([CITE], ApJ, 98, 595) and two datasets HST photometry with JHK_s photometry from the 2MASS + I band photometry from Magnier et al. ([CITE], A&A, 96, 379). The mean extinctions within the associations were estimated in two independent ways and the stellar masses were determined by use of probabilistic techniques. The derived slope of the IMF is close to the universal Salpeter's law and to recent estimates for massive stars' IMF in the Galaxy and in the Magellanic Clouds.