Skip to Main content Skip to Navigation
Theses

Formation d'étoiles massives en amas : conditions initiales, origine des masses stellaires et éjections protostellaires

Abstract : The research I have performed during my PhD addresses three major challenges of the star formation field: constraining, observationally, the earliest phases of high-mass star formation – the so-called prestellar stage, studying the origin of the stellar masses, and characterizing the process of protostellar accretion-ejection.Going beyond the current paradigms of star formation requires studying star-forming regions which are more representative of the general mode of star formation in the Milky Way. To this purpose I have used ALMA observations of W43-MM1, a young located at 5.5 kpc distance from the Sun, which presents a high star formation rate. The first step of my work has been to identify and characterize cores in the continuum image. I discovered 131 cores about 2400 AU in size which have mass between 1 and 100 Msun. I measured their mass distribution (CMF) and found a slope of -0.96 +/- 0.13 on 1.6 - 100 Msun that is markedly flatter than the reference Salpeter slope of the IMF on that range, -1.35. This means an overabundance of high-mass cores - and thus high-mass stars -compared to the number expected by the current models of star formation. Possible explanations imply either that star-formation is atypical in W43-MM1 (variably in the Milky Way) or that high-mass stars form at different time than low-mass stars in a cluster (star formation would not be a continuous process).I have characterized these cores using CO(2-1) and SiO(5-4) lines and revealed a rich cluster of 45 outflow lobes from 27 cores covering the whole mass range and including 11 high-mass cores (M>16 Msun). I have also used the detection of Complex Organic Molecules (COMs), typically detected in warm environments like hot cores, as indicator of the protostellar activity. 12 out of the 13 high-mass cores in W43-MM1 have eventually been characterized as protostellar, leaving one good high-mass prestellar core candidate. These statistics raises question about the universality of a prestellar phase for high-mass stars and suggests that the core-fed models for high-mass star formation cannot generally apply. The protostellar outflows also bring valuable information on the accretion/ejection history. I have studied the kinematics of high-velocity molecular jets that divide into knots using Position-Velocity diagrams. I have shown that the complex velocity structures of these knots hide a strong variability, and evaluated the associated timescale between two ejections to be about 500 yr. This is reminiscent of the values obtained between accretion burst in FU Orionis stars.
Complete list of metadatas

Cited literature [422 references]  Display  Hide  Download

https://tel.archives-ouvertes.fr/tel-02527680
Contributor : Abes Star :  Contact
Submitted on : Wednesday, April 1, 2020 - 12:54:15 PM
Last modification on : Wednesday, October 14, 2020 - 4:19:25 AM

File

NONY_2019_archivage.pdf
Version validated by the jury (STAR)

Identifiers

  • HAL Id : tel-02527680, version 1

Collections

Citation

Thomas Nony. Formation d'étoiles massives en amas : conditions initiales, origine des masses stellaires et éjections protostellaires. Astrophysique stellaire et solaire [astro-ph.SR]. Université Grenoble Alpes, 2019. Français. ⟨NNT : 2019GREAY054⟩. ⟨tel-02527680⟩

Share

Metrics

Record views

150

Files downloads

62