EPoS Contribution
EPoS Contribution
Observational Evidence for Massive Clusters in Compact and Ultracompact HII regions

James Furness
University of Sheffield, Sheffield, UK
Determining the stellar content of ultracompact HII regions is to give an idea of the primordial stellar distribution, before any binary or dynamic interations can disrupt the stars. The ultracompact phase is the earliest time at which zero age main sequence stars can be detected. Initial far-infrared studies using Spitzer/MIPS inferred the presence of massive star clusters following a high-mass Kroupa IMF, within the extended, lower density 'compact' region of a sample of Galactic ultracompact HII regions. Further work incorporating mid-infrared imaging and spectroscopy from VLT/VISIR and GEMINI/MICHELLE looks at the ultracompact HII region itself with very high spatial resolution (~0.3" or ~0.008pc at 5kpc at 10 microns), allowing detection of the individual embedded early-type stars via their mid-infrared fine structure lines (which are not seen in cooler stars). We obtain observational evidence that early-type stars prefer to form with other high mass counterparts.