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Structure en vitesse des enveloppes protostellaires : Effondrement gravitationnel et rotation

Abstract : Stars form from the gravitational collapse of prestellar condensations in molecular clouds. The major aim of this thesis is to compare the predictions of collapse models with observations of both very young (class 0) protostars and starless condensations in millimeter molecular lines. We wish to understand what determines the masses of forming stars and whether the initial conditions have an effect on the dynamical evolution of a condensation. Using a Monte-Carlo radiative transfer code, we analyze rotation and infall spectroscopic signatures to study the velocity structure of a sample of protostellar condensations. We show that the envelope of the class 0 protostar IRAM 04191 in the Taurus molecular cloud is undergoing both extended, subsonic infall and fast, differential rotation. We propose that the inner part of the envelope is a magnetically supercritical core in the process of decoupling from the ambient cloud still supported by the magnetic field. We suggest that the kinematical properties observed for IRAM 04191 are representative of the physical conditions characterizing isolated protostars shortly after point mass formation. On the other hand, a similar study for the prestellar condensations of the Rho Ophiuchi protocluster yields mass accretion rates that are an order of magnitude higher than in IRAM 04191. This suggests that individual protostellar collapse in clusters is induced by external disturbances. Moreover, we show that the condensations do not have time to orbit significantly through the protocluster gas before evolving into protostars and pre-main-sequence stars. This seems inconsistent with models which resort to dynamical interactions and competitive accretion to build up a mass spectrum comparable to the stellar initial mass function. We conclude that protostellar collapse is nearly spontaneous in regions of isolated star formation such as the Taurus cloud but probably strongly induced in protoclusters.
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https://tel.archives-ouvertes.fr/tel-00003279
Contributor : Arnaud Belloche <>
Submitted on : Thursday, August 28, 2003 - 12:37:20 PM
Last modification on : Monday, February 10, 2020 - 6:12:38 PM
Long-term archiving on: : Wednesday, September 12, 2012 - 10:15:27 AM

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  • HAL Id : tel-00003279, version 1

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Arnaud Belloche. Structure en vitesse des enveloppes protostellaires : Effondrement gravitationnel et rotation. Astrophysique [astro-ph]. Université Paris Sud - Paris XI, 2002. Français. ⟨tel-00003279⟩

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