DISSECTING HIGH-MASS PROTOSTARS AND EMERGING HOT CORES

Timea Csengeri –  Laboratoire d’Astrophysique de Bordeaux

Most stars form in multiple systems and clusters, especially OB type stars are frequently found in a clustered environment. Yet, the early phase of star and cluster formation is still poorly understood, and little attention has been paid to the complex interplay between the physical processes and the chemical evolution of the gas. The enrichment of the star forming gas in complex organic molecules (COMs) is associated with emerging deeply embedded heating sources, referred to as hot cores. Neither the physical and chemical conditions at the emergence of COMs, nor the diversity of COMs among hot cores is well established. I will discuss here results from the SPARKS survey and the ALMA-IMF Large program to elucidate the molecular composition of hot cores based on large samples of protostellar envelopes.

In addition to the brightest hot cores that exhibit a line rich spectrum, we have also identified a population of sources that are at moderate temperatures, close to the typical sublimation temperatures of COMs at about 100 K, corresponding to the early warm-up phase chemistry. Our results suggest that once thermal desorption starts, the protostellar envelopes become enriched in a variety of COMs, such as methanol, ethanol, heavy complex cyanides and formamide, consistent with models where a large fraction of COMs can be formed on the grains which then sublimate to the gas phase due to the onset of protostellar heating. We find that the molecular composition of the gas is well characterised by mainly O-bearing COMs in the early warm-up phase, while heavy complex cyanides trace better the emerging heated gas regions with higher temperatures. I will also present our results using molecular line emission to dissect high-mass protostellar cores that allowed us to pinpoint, for the first time, accretion shocks around a high-mass protostar.

https://univ-tlse3-fr.zoom.us/j/93683865178?pwd=MlFHMk1UTDlWOUFLWTNJQk5WQzhxdz09