Wednesday, 11th May at 2.00pm @ the JAC

ABSTRACT: I will present the results of a SIMBA 1.2 millimetre continuum emission survey toward regions previously identified as harbouring a methanol maser and/or a UC HII region, typically indicative of massive star formation. We have idenitified a large number of other sources in the SIMBA maps, which are devoid of maser and radio continuum emission. These `mm-only' cores may be an entirely new class of source that represents an earlier stage in the evolution of massive stars, prior to the onset of methanol maser emission. Or, they may harbour protoclusters which do not contain any high mass stars (i.e. below the HII region limit). Alternatively, they may represent a cross section of both, where the more massive mm-only cores are precursors to the methanol maser and the least massive mm-only cores will form intermediate mass stars.

Analysis of the mm-only sources shows that they are less massive (M_av = 0.9 x 10^{3} Msun), and smaller (R_av = 0.4 pc) than sources with methanol maser and/or radio continuum emission, which collectively have a mean mass of 2.5 x 10^{3} Msun and a mean radius of 0.7pc.