25 Novembre – Thesis defense - Jordan Molet
14 h Salle : Univers - Bâtiment B18N (Pessac)
Molecular analysis of massive cores in the star forming region W43-MM1.
Nowadays, understanding the formation of massive stars is one the main issues in astrophysics because of their important role in the evolution of the interstellar medium, and more particularly, for its chemistry. Although the existence of massive prestellar cores has not been confirmed so far, several candidates have been discovered recently thanks to the performance of new large radio interferometers.
The subject of my thesis concerns the star-forming region W43-MM1, in which there are many massive dense cores at different evolutionary stages. In particular, I focused on the characterisation of the very last and best prestellar candidate, as well as the molecular content of the richest cores in the region. For this purpose, I used data with high spatial (0.5’’, or 2400 au) and spectral (0.2 to 1.6 km/s) resolutions from the ALMA interferometer. In addition, I used a large spectral survey obtained with the IRAM 30-meter telescope, observed with resolutions ranging from 9’’ to 30’’ (0.2 to 0.8 pc) and from 0.2 to 0.7 km/s. With these data, I was able to identify molecules associated with the extended emission, and to reveal the molecular richness of the region. I have thus detected many complex molecules. With the most abundant ones, in particular methanol (CH3OH), methyl formate (CH3OCHO) and dimethyl ether (CH3OCH3), I have estimated the temperatures and compared the molecular densities of the different cores. For a better characterisation of the weakest molecular emissions, I developed a method to subtract the continuum emission of the dust grains. Thanks to that, I was able to evaluate the temperature of the massive prestellar core candidate and confirmed that it is a very unique object, which deserves particular attention in order to understand the first stages of the formation of massive stars.