2003ApJ...588..353H

We have conducted a deep Q-band (λ∼7 mm) search with the Very Large Array (VLA) toward OMC-1 for the lowest energy conformation (conformer I) of glycine (NH₂CH₂COOH) in four rotational transitions: 6₁₅-5₁₄, 6₂₄-5₂₃, 7₁₇-6₁₆, and 7₀₇-6₀₆. Our VLA observations sample the smallest scale structures to date in the search for glycine toward OMC-1. No glycine emission features were detected. Thus, if glycine exists in OMC-1, it is below our detection limit, or it is more spatially extended than other large molecules in this source, or it is primarily in its high-energy form (conformer II). Our VLA glycine fractional abundance limits in OMC-1 are comparable to those determined from previous IRAM 30 m measurements–somewhat better or worse depending on the specific source model–and the entire ∼1' primary beam of the VLA was searched while sensitive to an areal spatial scale ∼150 times smaller than the 24" beam of the IRAM single-element telescope. In the course of this work, we detected and imaged the 4₁₄-3₁₃A and E transitions of methyl formate (HCOOCH₃) and also the 2₀₂-1₀₁transition of formic acid (HCOOH). Since formic acid is a possible precursor to glycine, our glycine limits and formic acid results provide a constraint on this potential formation chemistry route for glycine in OMC-1.