Interstellar Glycolaldehyde, Methyl Formate, and Acetic Acid: Remarkably Bi-modal, Log-Linear Abundance Patterns in Star Forming Regions

The relative abundances of the structural isomers methyl formate, glycolaldehyde, and acetic acid are derived for the MM1 and MM2 massive star-forming regions in the NGC 6334 I complex which are separated by ~4000 AU. When compared with the relative abundances of these molecules in 13 other sources, a clear bi-modal linear distribution is exhibited in the glycolaldehyde abundance when plotted as a function of methyl formate. No such distribution is evident with acetic acid. The two linear trends in glycolaldehyde are comprised of star-forming regions with a variety of masses, suggesting that there must be some other common parameter that is heavily impacting the formation of the aforementioned isomers. The linear trends are indicative of some demonstrable differentiation in these cores; studying the abundances of these isomers may give a clue as to the integral chemical processes ongoing in a variety of protostellar environments.