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The Most Luminous Protostars in Molecular Clouds:A Hint to Understand the Stellar Initial Mass Function

Published online by Cambridge University Press:  25 September 2002

K. Dobashi
Affiliation:
Department of Astronomy and Earth Sciences, Tokyo Gakugei University, Koganei, Tokyo 184-8501, Japan
Y. Yonekura
Affiliation:
Department of Earth and Life Sciences, Osaka Prefecture University, Sakai, Osaka 599-8531, Japan
T. Matsumoto
Affiliation:
Department Humanity and Environment, Hosei University, Chiyoda-ku, Tokyo 102-8160, Japan
M. Momose
Affiliation:
Institute of Astrophysics and Planetary Science, Ibaraki University, Mito 310-8512, Japan
F. Sato
Affiliation:
Department of Astronomy and Earth Sciences, Tokyo Gakugei University, Koganei, Tokyo 184-8501, Japan
J.P. Bernard
Affiliation:
IAS, Bât. 121, Campus d'Orsay, 91405 Orsay Cedex, France
H. Ogawa
Affiliation:
Department of Earth and Life Sciences, Osaka Prefecture University, Sakai, Osaka 599-8531, Japan
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Abstract

The maximum luminosity of protostars forming in molecular clouds isinvestigated as a function of the parent cloud mass on the basis of arich cloud sample searched for in the literature. In total, we gathered499 molecular clouds among the published data, out of which 243clouds are found to be associated with candidates for protostars selectedfrom the IRAS point source catalog. A diagram of the maximum stellarluminosity in each cloud and the parent cloud mass shows that theyoung stars in the clouds associated withregions are apparentlymore luminous than those in clouds away from HIIregions over theentire cloud mass range investigated (1 < MCL/M < 106).In addition, wefound that there are well-defined upper and lower limits in themaximum stellar luminosity distribution with the lower limit having asteeper dependence on the cloud mass(LMAX ∝ MCL1.5) than the upperone (LMAX ∝ MCL0.8). All these featurescould be naturally accounted forif we assume that the luminosity function of protostars is controlled by thecloud mass and the external pressure imposed on the cloud surface. Weintroduce a simple model for the stellar luminosity function as afunction of these quantities.

Type
Research Article
Copyright
© EAS, EDP Sciences, 2002

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