High mass star formation in the infrared dark cloud G11.11-0.12

Free access article

Issue		A&A Volume 447, Number 3, March I 2006


Page(s)		929 - 936
Section		Interstellar and circumstellar matter
DOI		http://dx.doi.org/10.1051/0004-6361:20042145

A&A 447, 929-936 (2006)
DOI: 10.1051/0004-6361:20042145

High mass star formation in the infrared dark cloud G11.11-0.12

T. Pillai, F. Wyrowski, K. M. Menten and E. Krügel

Max-Planck-Institut für Radioastronomie, Auf dem Hügel 69, 53121 Bonn, Germany
e-mail: thushara@mpifr-bonn.mpg.de

(Received 8 October 2004 / Accepted 22 September 2005 )

Abstract
We report detection of moderate to high-mass star formation in an infrared dark cloud (G11.11-0.12) where we discovered class II methanol and water maser emission at 6.7 GHz and 22.2 GHz, respectively. We also observed the object in ammonia inversion transitions. Strong emission from the (3, 3) line indicates a hot (60 K) compact component associated with the maser emission. The line width of the hot component (4 $\mathrm{km\,s^{-1}}$ ), as well as the methanol maser detection, are indicative of high mass star formation. To further constrain the physical parameters of the source, we derived the spectral energy distribution (SED) of the dust continuum by analysing data from the 2MASS survey, HIRAS, MSX, the Spitzer Space Telescope, and interferometric 3 mm observations. The SED was modelled in a radiative transfer program: a) the stellar luminosity equals ${\sim}$ 1200 $L_\odot$ corresponding to a ZAMS star of 8 $M_\odot$ ; b) the bulk of the envelope has a temperature of 19 K; c) the mass of the remnant protostellar cloud in an area $8\times 10^{17}$ cm or 15'' across amounts to 500 $M_\odot$ , if assuming standard dust of the diffuse medium, and to about 60 $M_\odot$ , should the grains be fluffy and have ice mantles; d) the corresponding visual extinction towards the star, $A_{\rm V}$ , is a few hundred magnitudes. The near IR data can be explained by scattering from tenuous material above a hypothetical disk. The class II methanol maser lines are spread out in velocity over 11 km s^-1. To explain the kinematics of the masing spots, we propose that they are located in a Kepler disk at a distance of about 250 AU. The dust temperatures there are around 150 K, high enough to evaporate methanol-containing ice mantles.

Key words: masers -- stars: formation -- molecular data -- radiative transfer -- astronomical databases: miscellaneous

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