2007ApJ...655L..37R

We present high-sensitivity observations of the complex organic molecules (COMs) CH₃OH, C₂H₅OH, HCOOCH₃, HCOOH, and H₂CO and of SiO toward the quiescent dark cloud L183 and the molecular outflow L1448-mm. We have not detected C₂H₅OH, HCOOCH₃, or SiO in L183 or in the quiescent gas of L1448-mm. The abundances of CH₃OH, H₂CO, and SiO are enhanced by factors of 4-20 in the shock precursor component, and those of CH₃OH and SiO by 3 and 4 orders of magnitude in the shocked gas, without substantial changes (less than a factor of 2) in the abundances of C₂H₅OH and HCOOCH₃relative to that of CH₃OH. The large enhancements of SiO and CH₃OH can be explained by the shock ejection of an important fraction of the grain mantle material into the gas phase. Our upper limits to the C₂H₅OH/CH₃OH and HCOOCH₃/CH₃OH ratios are consistent with the rather constant ratios measured in hot cores and Galactic center clouds. However, the upper limits to the HCOOCH₃/CH₃OH and HCOOH/CH₃OH ratios are at least 1 order of magnitude smaller than those found in``hot corinos'' surrounding low-mass protostars. We speculate that the observed abundances of COMs in different objects are consistent with a sort of ``universal'' grain mantle composition that is locally changed by the processes of low-mass star formation.