The formation of high-mass stars - accretion and/or merging?

• Applicant: Dr. Vera Hoffmeister
• Subject Area: Astrophysics and Astronomy
• Term: from 2010 to 2012
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 167039162

The young massive cluster in M17 is ideal to study early phases of high-mass star formation. On the basis of new existing VLT data and/or accepted VLT and CAHA proposals the following investigations are proposed:High-mass protostars: Optical and infrared spectroscopy for a number of high-mass protostars will place these objects unambiguously onto recent evolutionary tracks. These stars seem to be in a rare evolutionary stage supporting the high M accretion scenario and representing the missing link between luminous high-mass cores and ultra-compact HII regions.Multiplicity of young OB stars: The binary fraction and the stellar rotation have not yet been studied in a newly born OB cluster. Using AO imaging and HR spectroscopy the multiplicity and the rotational velocities of 45 very young OB stars in M17 will provide clues to the connections among these quantities This study will show if massive stars are born as rapid rotators, will help us understand the role of multiplicity in their formation, and will correct biases of the upper IMF which is typically based on unresolved OB cluster members.Disks around high-mass stars: 104 massive YSOs of M17 with CO band-head absorption, X-ray emission and infrared excess are obviously associated with circumstellar material. New high-resolution CRIRES spectra will reveal the nature of the circumstellar CO.Variability of high-mass stars: An ongoing NIR monitoring study of the M17 cluster will show whether young high-mass stars display any variability analogous to low-mass PMS stars: Are there flares due to fossil magnetic fields? Are there dynamically induced flares of various sorts like e.g. accretion events from companion disks or interactions with circumstellar matter? Do massive stars undergo FU Ori outbursts?

• DFG Programme: Research Grants