An observational study of massive star forming regions at radio wavelengths

In their early stages, massive stars have a profound impact on their hosting cloud as reflected by signposts like shocks, bars and shells of swept material resulting from prominent stellar winds, or photo-ionized (HII) regions produced by energetic irradiance. This activity must be taken into account in the study of the mechanism of formation of either massive stars or nearby lower mass companions affected by such harsh conditions. It is known that HII regions are strong centimeter emitters and, thus, radio observations are important to explore the sites of massive star formation. In this talk I will show the results of an observational campaign, using the Very Large Array (VLA), over several star forming regions with already ongoing massive stellar activity, which spans from evolved HII regions to very young Ultra-Compact (UC) HII regions. As we want to explore the closest vicinity of massive stars, we focus on the most compact components (of few hundreds of AUs). We found a striking richness of compact radio sources present in these regions, whose nature is unclear and probably not unique. A deeper analysis suggests that some of these sources are disks being evaporated by the energetic radiation of massive stars, affecting the disk structure and evolution around high mass and low mass nearby stellar objects, and casting doubt on their capability to form planets.

Furthermore, as the HII region later expands into the molecular cloud, entire stellar populations are revealed in radio emission, as seen in the M17 region, where the highly variable gyro synchrotron radiation of a considerable number of pre-stellar objects (> 80) detected by us suggests an episodic formation of a new generation of stars in the region.

16/03/2023 - 12:30
Josep Maria Masqué
Universidad de Guanajuato, Mexico