Model of the W3(OH) Environment Based on Data for Both Maser and ?Quasi-Thermal? Methanol Lines

Abstract

Abstract. In studies of the environment of massive young stellar objects, recent progress in both observations and theory allows a unified treatment of data for maser and 'quasi-thermal' lines. Interferometric maser images provide information on the distribution and kinematics of masing gas on small spatial scales. Observations of multiple masing transitions provide constraints on the physical parameters.Interferometric data on 'quasi-thermal' molecular lines permits an investigation of the overall distribution and kinematics of the molecular gas in the vicinity of young stellar objects, including those which are deeply embedded. Using multiple transitions of different molecules, one can obtain good constraints on the physical and chemical parameters. Combining these data enables the construction of unified models, which take into account spatial scales differing by orders of magnitude.Here we present such a combined analysis of the environment around the ultracompact HII region in W3(OH). This includes the structure of the methanol masing region, physical structure of the near vicinity of W3(OH), detection of new masers in the large-scale shock front and embedded sources in the vicinity of the TW young stellar object.Keywords: radiolines -ISM: molecules Possibility of combined analysis of data on maser and 'quasi-thermal' linesModern studies of the kinematical, physical and chemical status of star forming regions are largely based on the information delivered by emission in molecular lines. Different molecular transitions have different excitation temperatures, as a result of the radiative and collisional population exchange between quantum levels. In the stationary case these take the form of pumping cycles (see, e.g., Sobolev and Deguchi, 1994). Excitation states of molecular transitions are mostly characterized by positive excitation temperatures and, hence, the optical depths

Modelling of Cosmic Molecular Masers: Introduction to a Computation Cookbook

“…Another type of modelling studies aims to reproduce general characteristics of the observational data because searching for exact coincidence is impossible, for example because of the stochastic character of the emission. Reproducing spectra and images for CH 3 OH masers in Ori-KL was done by Sobolev et al (1998), for CH 3 OH masers in W3(OH) by Sobolev et al (2005), and for SiO masers in o Cet by Gray et al (2009). Maser variability was addressed in Sobolev et al (2003) and Gray (2005).…”