Molecule-dependent Abundance Behavior of Oxygen-bearing Complex Organics in High-Mass Star-Forming Regions: A Uniform 50-source Survey

Abstract

We present a uniform IRAM-30\,m survey analysis of four oxygen-bearing complex organic molecules (COMs), methanol (CH${}_3$OH), acetaldehyde (CH${}_3$CHO), methyl formate (CH${}_3$OCHO), and dimethyl ether (CH${}_3$OCH${}_3$), toward 50 high-mass star-forming regions (HMSFRs) associated with 6.7\,GHz methanol masers. Column densities were derived through a homogeneous rotation-diagram approach, with CH${}_3$CN used as a proxy excitation-temperature reference when needed. In CH${}_3$OH-normalized abundance-ratio space, CH${}_3$OCHO/CH${}_3$OH and CH${}_3$OCH${}_3$/CH${}_3$OH show the strongest pairwise correlation, whereas the correlations involving CH${}_3$CHO are weaker. No clear monotonic trends are found with Galactocentric distance or beam-averaged H${}_2$ column density. Comparison with previous observations places the CH${}_3$OCHO--CH${}_3$OCH${}_3$ behavior within the range of earlier abundance-ratio measurements, while CH${}_3$CHO shows larger inter-study variation. A representative warm-up chemical model is used only for qualitative comparison with the observed abundance ranges, which are most closely matched during the decline from the post-desorption abundance peaks in the model. These results provide homogeneous beam-averaged abundance-ratio constraints for common O-bearing COMs in high-mass star-forming regions and show that their source-to-source behavior is molecule-dependent rather than fully described by a single common abundance pattern.

9 pages, 6 figures, 3 tables, accepted for publication in A&A