Author(s): , , , , ,
Institution(s): 1. Cardiff University, 2. IAPS - INAF, 3. MPE, 4. University of Manchester
Clouds seen in absorption against the diffuse mid-infrared radiation field, infrared dark clouds (IRDCs), trace quiescent, dense gas which is not yet dominated by the feedback from young stars and these objects are therefore important targets for the study of the initial conditions for star formation. A recent analysis of the multi-wavelength Herschel survey of the Galactic plane, Hi-GAL, has been used to identify and characterise the mass, luminosity and temperature of the compact massive sources in the IRDCs in the Spitzer Dark Cloud catalogue. The 70 micron Hi-GAL observations have been used to identify those sources which already contain young protostars and those that do not. The sources range in mass up 104 M⊙ and up to 105 L⊙ in luminosity. The most massive sources with highest mass to luminosity ratios which are not associated with 70 micron emission are excellent candidates for high mass starless clumps (HMSC). These objects have high enough mass to form compact stellar clusters and so the properties of these HMSCs provide the initial conditions for the formation of stellar clusters.
In this presentation we will discuss the results of the Hi-GAL analysis of the Spitzer clouds and the properties of both the massive protostellar clumps and starless clumps identified. We will then describe recent follow-up observations of a sample of HMSCs including discussing their kinematic properties which provide important insights into how these precusors to stellar clusters form.