SIMBAD references

We have searched for HDS emission in a small number of hot cores. Using observations of H₂³⁴S, we have derived upper limits to the [HDS]/[H₂S] abundance ratio. The upper limits, which are close to 10^–3 can be interpreted in two ways, depending on whether grain surface reactions contribute to the formation of H₂S. If grains do not dominate, then the H₂S observed is formed in hot, post-shocked gas and a ratio close to the cosmic [D]/[H] ratio is expected for [HDS]/[H₂S]. This scenario is consistent with our upper limits and with the relatively low abundance ratio found for [HDO]/[H₂O] in hot cores but does not seem to account for all of the molecular [D]/[H] ratios observed in hot cores. If grains do dominate the formation of H₂S, then the observed upper limit to the ratio is consistent with the formation of `hot core ices' at a temperature of 60-80 K, close to the temperature at which cometary ices are thought to form.