SCYON Abstract

Received on December 2 2003

Evidence for a fundamental stellar upper mass limit from clustered star formation

Authors	Carsten Weidner, Pavel Kroupa
Affiliation	Institut für Theoretische Physik und Astrophysik der Universität Kiel, D-24098 Kiel, Germany
Accepted by	Monthly Notices of the Royal Astronomical Society
Contact	weidner@astrophysik.uni-kiel.de
URL	http://xxx.uni-augsburg.de/abs/astro-ph/0310860
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Abstract

The observed masses of the most massive stars do not surpass about 150 Mo. This may either be a fundamental upper mass limit which is defined by the physics of massive stars and/or their formation, or it may simply reflect the increasing sparsity of such very massive stars so that observing even higher-mass stars becomes unlikely in the Galaxy and the Magellanic Clouds. It is shown here that if the stellar initial mass function (IMF) is a power-law with a Salpeter exponent (alpha = 2.35) for massive stars then the richest very young cluster R136 seen in the Large Magellanic Cloud (LMC) should contain stars with masses larger than 750 Mo. If, however, the IMF is formulated by consistently incorporating a fundamental upper mass limit then the observed upper mass limit is arrived at readily even if the IMF is invariant. An explicit turn-down or cutoff of the IMF near 150 Mo is not required; our formulation of the problem contains this implicitly. We are therefore led to conclude that a fundamental maximum stellar mass near 150 Mo exists, unless the true IMF has alpha > 2.8.