EDP Sciences
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Volume 426, Number 2, November I 2004
Page(s) 495 - 501
Section Galactic structure, stellar clusters and populations
DOI http://dx.doi.org/10.1051/0004-6361:20040414

A&A 426, 495-501 (2004)
DOI: 10.1051/0004-6361:20040414

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

T. Veltchev1, 2, P. Nedialkov1, 2 and G. Borisov3

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)

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. (1995, ApJ, 98, 595) and two datasets HST photometry with JHK$_{\rm s}$ photometry from the 2MASS + I band photometry from Magnier et al. (1992, 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 $\Gamma=-1.59 \pm 0.09$ is close to the universal Salpeter's law and to recent estimates for massive stars' IMF in the Galaxy and in the Magellanic Clouds.

Key words: galaxies: individual: M 31 -- galaxies: stellar content -- galaxies: ISM -- stars: luminosity function, mass function -- stars: early-type -- stars: supergiants

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