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Paper: From Large Scale Surveys of the Galaxy to High Resolution Observations with ALMA
Volume: 476, New Trends in Radio Astronomy in the ALMA Era
Page: 231
Authors: Bronfman, L.; Merello, M.
Abstract: A CS(2-1) survey of OB star forming regions provides statistics of their distribution in the Galaxy. The complete scenario of massive star formation for one particular GMC, at a distance of 1.6 kpc, is revealed through 1.2 mm continuum observations for spatial scales from 1 pc to 50 pc. Using large scale CO and C18O maps from NANTEN at 2.5′ resolution, we identified toward the peak of C18O one of the most luminous regions of high-mass star formation in the Galaxy, G331.5, toward the tangent of Norma spiral arm, at a distance of 7.5 kpc. Observations at 1.2 mm continuum emission with SIMBA at SEST reveal the presence of a cluster of six massive millimeter clumps, with high bolometric luminosity, making G331.5 one of the most densely populated GMC cores known so far. High density molecular tracers reveal the presence, in the center of the most massive clump, of a compact, highly massive and energetic molecular outflow, with a velocity width reaching 160 km s-1 (fwzp). Further interferometric continuum observations at 3.6 cm and 6 cm shows that this powerful outflow is associated with a compact radio continuum source, likely producing highly ionized stellar wind. ALMA observations were carried in band 7 to this unresolved molecular outflow. SiO and H13CO+ observations unveil a shell-like structure toward the ambient velocity of the source, evidence of an isotropic high speed wind. The derived crossing time for this source indicates that the molecular outflow in G331.5 is one of the youngest outflow found around an OB star.
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