During the formation of massive stars, fragmentation takes place on various spatial scales from giant molecular clouds down to disk scales. At the earliest evolutionary stages, high-mass protostars are still deeply embedded in a core envelope (< 0.1pc) within their parental molecular cloud and can be studied best at high spatial resolution with interferometers at mm wavelengths.
With observations at 1 mm and 3 mm with NOEMA and ALMA toward a sample of high-mass star-forming regions we characterize the physical properties of fragmented cores. Our sample covers evolutionary phases ranging from young infrared dark clouds to evolved ultra-compact HII regions. The continuum of the sample shows a large diversity of fragmentation properties throughout the regions, typically revealing many fragmented cores within a single region. Using the continuum and spectral line emission, we characterize the physical structure of the cores (mass, temperature, and density).
We find evolutionary trends on core scales for the temperature power-law index q (T~r^-q) increasing from 0.1 to 0.7 from cores located in infrared dark clouds to cores located in hot core regions, while the density power-law index p (n~r^-p) stays constant with a mean value around 2. However, on the larger clump scales throughout the evolutionary phases the density profile flattens from p=2.2 to p=1.2. By characterizing this large statistical sample of individual fragmented cores, we reveal that the physical properties, such as the temperature and density profile, evolve even during the earliest evolutionary phases in high-mass star-forming regions. These findings provide observational constraint for theoretical models describing the formation of massive stars.