The Search for a Complex Molecule in a Selected Hot Core Region: A Rigorous Attempt to Confirm trans-Ethyl Methyl Ether toward W51 e1/e2

TL;DR

This study conducted rigorous searches for trans-ethyl methyl ether in star-forming regions W51 e1/e2 and Sgr B2(N-LMH), failing to confirm its presence and emphasizing the need for careful spectral analysis in molecular identification.

Contribution

The paper provides the first thorough non-detection of trans-ethyl methyl ether in these regions, challenging previous claims and highlighting the importance of rigorous verification in astrochemical studies.

Findings

No detection of tEME in W51 e1/e2 or Sgr B2(N-LMH)

Established upper limits for tEME column densities

Questioned previous claims of tEME detection in interstellar medium

Abstract

An extensive search has been conducted to confirm transitions of \textit{trans}-ethyl methyl ether (tEME, C$_2$H$_5$OCH$_3$), toward the high mass star forming region W51 e1/e2 using the 12 m Telescope of the Arizona Radio Observatory (ARO) at wavelengths from 2 mm and 3 mm. In short, we cannot confirm the detection of tEME toward W51 e1/e2 and our results call into question the initial identification of this species by \citet{FuchsSpace}. Additionally, reevaluation of the data from the original detection indicates that tEME is not present toward W51 e1/e2 in the abundance reported by Fuchs and colleagues. Typical peak-to-peak noise levels for the present observations of W51 e1/e2 were between 10 - 30 mK, yielding an upper limit of the tEME column density of $\leq$ 1.5 $\times$ 10$^{15}$ cm$^{-2}$. This would make tEME at least a factor 2 times less abundant than dimethyl ether (CH$_3$OCH$_3$) toward W51 e1/e2. We also performed an extensive search for this species toward the high mass star forming region Sgr B2(N-LMH) with the NRAO 100 m Green Bank Telescope (GBT). No transitions of tEME were detected and we were able to set an upper limit to the tEME column density of $\leq$ 4 $\times$ 10$^{14}$ cm$^{-2}$ toward this source. Thus, we are able to show that tEME is not a new molecular component of the interstellar medium and that an exacting assessment must be carried out when assigning transitions of new molecular species to astronomical spectra to support the identification of large organic interstellar molecules.