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2009MNRAS.394..323P - Mon. Not. R. Astron. Soc., 394, 323-339 (2009/March-3)
Physical and chemical conditions in methanol maser selected hot cores and UCHII regions.
PURCELL C.R., LONGMORE S.N., BURTON M.G., WALSH A.J., MINIER V., CUNNINGHAM M.R. and BALASUBRAMANYAM R.
Abstract (from CDS):
The molecular line data have been used to derive virial and local thermodynamic equilibrium masses, rotational temperatures and chemical abundances in the clumps, and these properties have been compared between subsamples associated with different indicators of evolution. The greatest differences are found between clumps associated with 8.6GHz radio emission, indicating the presence of an Ultra-Compact Hii (UCHii) region, and `isolated' masers (without associated radio emission), and between clumps exhibiting CH3 CN emission and those without. In particular, thermal CH3 OH is found to be brighter and more abundant in UCHii regions and in sources with detected CH3CN, and may constitute a crude molecular clock in single dish observations.
Clumps associated with 8.6GHz radio emission tend to be more massive and more luminous than clumps without radio emission. This is likely because the most massive clumps evolve so rapidly that a Hyper-Compact Hii or UCHii region is the first visible tracer of star formation.
The gas mass to submm/infrared luminosity relation for the combined sample was found to be L ∝ M0.68, considerably shallower than expected for massive main-sequence stars. This implies that the mass of the clumps is comparable to, or greater than, the mass of the stellar content.
We also find that the mass of the hot core is correlated with the mass of the clump in which it is embedded.
Abstract Copyright: © 2009 The Authors. Journal compilation © 2009 RAS
Journal keyword(s): surveys - stars: formation - stars: pre-main-sequence - ISM: abundances - ISM: molecules
Simbad objects: 12
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