Abstract
Unbiased analysis shows that IRAS data reliably differentiate between the early and late stages of stellar evolution because objects at these stages clearly segregate in infrared color-color diagrams. Structure in these diagrams is primarily controlled by the density distribution of circumstellar dust. The density profile around older objects is the steepest, declining as r-2, while young objects have profiles that vary as r-3/2 and flatter. The different density profiles reflect the different dynamics that govern the different environments. Our analysis also shows that high-mass star formation is strongly concentrated within ~5 kpc around the Galactic center, in support of other studies.
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