SIMBAD references

To understand the roles of infall and protostellar evolution on the envelopes of massive young stellar objects (YSOs). The chemical evolution of gas and dust is traced, including infall and realistic source evolution. The temperatures are determined self-consistently. Both ad/desorption of ices using recent laboratory temperature-programmed-desorption measurements are included. The observed water abundance jump near 100K is reproduced by an evaporation front which moves outward as the luminosity increases. Ion-molecule reactions produce water below 100K. The age of the source is constrained to t∼8±4x10⁴yrs since YSO formation. It is shown that the chemical age-dating of hot cores at ∼fewx10³-10⁴yr and the disappearance of hot cores on a timescale of ∼10⁵yr is a natural consequence of infall in a dynamic envelope and protostellar evolution. Dynamical structures of ∼350AU such as disks should contain most of the complex second generation species. The assumed order of desorption kinetics does not affect these results.