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2-D and 3-D radiation transfer models of forming stars generally produce bluer 1-10 μm colors than 1-D models of the same evolutionary state and envelope mass. Therefore, 1-D models of the shortwave radiation will generally estimate a lower envelope mass and later evolutionary state than multidimensional models. 1-D models are probably reasonable for very young sources, or longwave analysis ($\lambda >100 \mu$m). In our 3-D models of high-mass stars in clumpy molecular clouds, we find no correlation between the depth of the 10 μm silicate feature and the longwave ($> 100 \mu$m) SED (which sets the envelope mass), even when the average optical extinction of the envelope is ${> }100$ magnitudes. This is in agreement with the observations of Faison et al. (1998) of several UltraCompact HII (UCHII) regions, suggesting that many of these sources are more evolved than embedded protostars.
We have calculated a large grid of 2-D models and find substantial overlap between different evolutionary states in the mid-IR color-color diagrams. We have developed a model fitter to work in conjunction with the grid to analyze large datasets. This grid and fitter will be expanded and tested in 2005 and released to the public in 2006.
