Journal Club//2011 3rd quarterJournal Club on 2011/07/12Determining the dynamics of the ultracompact HII region (UCHII) Monoceros R2 By Acension Fuente (OAN - IGN, Spain) Room L269 (former D18, 2nd floor) at ENS, 24 rue Lhomond, 13:30 to 14:30
Ultracompact (UC) HII regions constitute one of the earliest phases in the formation of a massive star and are characterized by extreme physical and chemical conditions (G>10^5 in units of Habing field and n>10^6 cm^-3). Their understanding is important for distinguishing the different processes in massive star formation (UV radiation vs shocks) and because they can be used as a template for other extreme photon-dominated regions (PDRs) such as the surface layers of circumstellar disks and the nuclei of starburst galaxies. The UC HII Mon R2 is the only one that can be spatially resolved with single-dish telescopes, including Herschel. It has been extensively studied at millimeter and submillimeter wavelengths and all evidences support a chemistry driven by the strong UV field while shocks play only a minor role. Its physical and kinematical structure is well known and current observations are well explained by an expanding envelope with v_e=0.5x(r/R_{out})^{-1} km/s triggered by the inner HII region. These observations, however, only probe the cold phase of the molecular gas (Tk < 100 K) which is clearly insufficient for the full understanding of the massive star formation process.
Last update 07-06-2011 03:28 pm / Marc JoosJournal Club archives
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