A sensitive very large array search for small-scale glycine emission toward OMC-1

We have conducted a deep Q-band (lambda similar to 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: 6(15)-5(14), 6(24)-5(23), 7(17)-6(16), and 7(07)-6(06). 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 similar to1' primary beam of the VLA was searched while sensitive to an areal spatial scale similar to150 times smaller than the 24" beam of the IRAM single-element telescope. In the course of this work, we detected and imaged the 4(14)-3(13) A and E transitions of methyl formate (HCOOCH3) and also the 2(02)-1(01) transition 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.