Methyl Formate, Dimethyl Ether, and Methanol

Methyl formate, dimethyl ether, and methanol also make significant contributions to the ALMA spectrum of Orion KL. However, it is well known that the spatial distribution of these oxygen bearing species is offset from the cyanide species already described above [1]. Not pointing at the emission peak of the oxygen bearing species results in distorted lineshapes. Therefore, we have not attempted to do detailed lineshape or intensity simulations of these species as we have done for the cyanides. Additionally, methanol requires at least a two-temperature description.

Nevertheless, it is useful to compare stick spectra simulations of all six of these species simultaneously with the ALMA results. Figure: Six Species Contribution shows such a comparison for a small portion of the ALMA spectrum of the Orion KL hot core region. In this simulation the cyanide species had the column densities and temperature (190 K) as above; and methyl formate, dimethyl ether, and methanol were all simulated at 150 K. The sticks are semi-quantitative (except for methanol). Although overlaps and convolutions significantly complicate the quantitative comparison of the stick spectrum with that of ALMA, many features are readily identifiable.