Relative Evolutionary Time Scale of Hot Molecular Cores with Respect to Ultra Compact HII Regions

Abstract

Using the Owens Valley and Nobeyama Radio Observatory interferometers, we carried out an unbiased search for hot molecular cores and ultracompact UC HII regions toward the high-mass star forming region G19.61--0.23. In addition, we performed 1.2 mm imaging with SIMBA, and retrieved 3.5 and 2 cm images from the VLA archive data base. The newly obtained 3 mm image brings information on a cluster of high-mass (proto)stars located in the innermost and densest part of the parsec scale clump detected in the 1.2 mm continuum. We identify a total of 10 high-mass young stellar objects: one hot core (HC) and 9 UC HII regions, whose physical parameters are obtained from model fits to their continuum spectra. The ratio between the current and expected final radii of the UC \HII regions ranges from 0.3 to 0.9, which leaves the possibility that all O-B stars formed simultaneously. Under the opposite assumption -- namely that star formation occurred randomly -- we estimate that HC lifetime is less than $\sim$1/3 of that of UCHII regions on the basis of the source number ratio between them.

arXiv comment13 pages, 2 figs, including a color fig

References in corpus (3)

• The Physical Conditions for Massive Star Formation: Dust Continuum Maps and Modeling
• The structure of molecular clumps around high-mass young stellar objects
• A Search for Mid-Infrared Emission from Hot Molecular Core Candidates

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• Infall, outflow, and rotation in the G19.61-0.23 hot molecular core
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• Hot Molecular Core Candidates in the Galactic Center 50 km/s Molecular Cloud
• The molecular environment of the Galactic star forming region G19.61-0.23