Methanol masers to study high-mass star formation

by Michele Pestalozzi (University of Hertfordshire)

Friday 20 Apr 2007, 10:15 → 11:15 Europe/Stockholm

FA 31

Context: Despite the crucial role that high-mass stars play in the Galaxy, the understanding of their formation remains one of the most challenging yet unsolved problems in astrophysics. The discrepancy in knowledge between low- and high-mass star formation has its origin in the difficulty of gathering sufficient and relevant observational facts on a large sample of similar objects. High-mass stars evolve more quickly and lie at larger distances from the solar neighbourhood than their low-mass counterparts, resulting in relatively few candidates studied in depth.
Methods: Methanol is ubiquitous where stars form but its bright maser emission seems exclusively associated with high-mass star formation. Observations of methanol masers give a twofold advantage: their large number in the Galaxy allows statistical study of the high-mass star formation history of the Milky Way, and their observation at high spatial resolution reveals details of the morphology and the dynamics of some selected objects.
Aims: The aim of this presentation is to illustrate the recent major achievements of the study of methanol masers in the context of high-mass star formation.
Results: The distribution of methanol masers follows the one of OB associations, confirming their association to high-mass star formation. This makes them also an optimal tool to pinpoint new high-mass star formation regions in the Galaxy to be studied in depth. More, the study of the luminosity function of masers allows to predict their total number in the Galaxy and their lifetime. Finally, methanol masers can accurately trace edge-on discs, the study of which reveals that high-mass star formation has some similarities to low-mass star formation.
Conclusions&Future: Methanol masers are a reliable tracer of high-mass star formation in the Milky Way. They also reveal discs around high-mass protostars. The recently started Methanol MultiBeam Survey (MMB) will cover the entire galactic plane and potentially reveal the actual population of methanol masers in the Galaxy. Together with large scale sub-millimetre continuum surveys, MMB will allow to filter out the even younger sources, making an important step forward in the identification of very young high-mass star forming regions and their study in depth through follow-up observational campaigns.