2007MNRAS.380.1703W

We report on Australia Telescope Compact Array observations of the massive star-forming region G305.2+0.2 at 1.2cm. We detected emission in five molecules towards G305A, confirming its hot core nature. We determined a rotational temperature of 26K for methanol. A non-local thermodynamic equilibrium excitation calculation suggests a kinematic temperature of the order of 200K. A time-dependent chemical model is also used to model the gas-phase chemistry of the hot core associated with G305A. A comparison with the observations suggest an age of between 2x10⁴ and 1.5x10⁵ yr. We also report on a feature to the south-east of G305A which may show weak Class I methanol maser emission in the line at 24.933GHz. The more evolved source G305B does not show emission in any of the line tracers, but strong Class I methanol maser emission at 24.933GHz is found 3arcsec to the east. Radio continuum emission at 18.496GHz is detected towards two HII regions. The implications of the non-detection of radio continuum emission towards G305A and G305B are also discussed.