Warm cores (or hot corinos) around low-mass protostellar objects show a rich
chemistry with strong spatial variations. This chemistry is generally
attributed to the sublimation of icy mantles on dust grains initiated by the
warming effect of the stellar radiation. We have used a model of the chemistry
in warm cores in which the sublimation process is based on extensive laboratory
data; these data indicate that sublimation from mixed ices occurs in several
well-defined temperature bands. We have determined the position of these bands
for the slow warming by a solar-mass star. The resulting chemistry is dominated
by the sublimation process and by subsequent gas-phase reactions; strong
spatial and temporal variations in certain molecular species are found to
occur, and our results are, in general, consistent with observational results
for the well-studied source IRAS 16293-2422. The model used is similar to one
that describes the chemistry of hot cores. We infer that the chemistry of both
hot cores and warm cores may be described by the same model (suitably adjusted
for different physical parameters).Comment: 11 pages, 5 figures, 2 tables. Accepted by MNRA