The Physical Conditions for Massive Star Formation: Dust Continuum Maps and Modeling

Fifty-one dense cores associated with water masers were mapped at 350 micron. These cores are very luminous, 10^3 < Lbol/Lsun < 10^6, indicative of the formation of massive stars. Dust continuum contour maps and photometry are presented for these sources. The spectral energy distributions and normalized radial profiles of dust continuum emission were modeled for 31 sources using a one-dimensional dust radiative transfer code, assuming a power law density distribution in the envelope, n = n_f (r/r_f)^{-p}. The best fit density power law exponent, p, ranged from 0.75 to 2.5 with <p> = 1.8 +/- 0.4. The mean value of p is comparable to that found in regions forming only low mass stars. The mean p is incompatible with a logatropic sphere (p = 1), but other star formation models cannot be ruled out. Different mass estimates are compared and mean masses of gas and dust are reported within a half-power radius determined from the dust emission and within a radius where the total density exceeds 10^4 cm^3. Evolutionary indicators commonly used for low mass star formation may have some utility for regions forming massive stars. For comparison with extragalactic star formation studies, the luminosity to dust mass ratio is calculated for these sources with a method most parallel to that used in studies of distant galaxies and is found to be similar to that seen in high redshift starburst galaxies.