2011ApJ...742...28W

Methanol (CH₃OH) is thought to be an important link in the chain of chemical evolution that leads from simple diatomic interstellar molecules to complex organic species in protoplanetary disks that may be delivered to the surfaces of Earthlike planets. Previous research has shown that CH₃OH forms in the interstellar medium predominantly on the surfaces of dust grains. To enhance our understanding of the conditions that lead to its efficient production, we assemble a homogenized catalog of published detections and limiting values in interstellar and preplanetary ices for both CH₃ OH and the other commonly observed C- and O-bearing species, H₂O, CO, and CO₂. We use this catalog to investigate the abundance of ice-phase CH₃ OH in environments ranging from dense molecular clouds to circumstellar envelopes around newly born stars of low and high mass.
Result. show that CH₃ OH production arises during the CO freezeout phase of ice-mantle growth in the clouds, after an ice layer rich in H₂ O and CO₂is already in place on the dust, in agreement with current astrochemical models. The abundance of solid-phase CH₃ OH in this environment is sufficient to account for observed gas-phase abundances when the ices are subsequently desorbed in the vicinity of embedded stars. CH₃ OH concentrations in the ices toward embedded stars show order-of-magnitude object-to-object variations, even in a sample restricted to stars of low mass associated with ices lacking evidence of thermal processing. We hypothesize that the efficiency of CH₃ OH production in dense cores and protostellar envelopes is mediated by the degree of prior CO depletion.