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 emissions 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 ( Â 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 3mm 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 ^ { \prime \prime } 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 _ { 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 .
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 .