Searching for Trans Ethyl Methyl Ether in Orion KL

TL;DR

This study reports the tentative detection and spatial distribution of trans Ethyl Methyl Ether in Orion KL, along with related molecules, providing insights into complex organic molecules in star-forming regions.

Contribution

First detection of trans Ethyl Methyl Ether in Orion KL with spatial mapping and comparison to related molecules, expanding knowledge of organic chemistry in space.

Findings

Trans EME mainly arises from the compact ridge of Orion.

Gauche-trans-n-propanol appears at the ethanol emission peak.

Column densities are approximately 4.0e15 and 1.0e15 cm^-2 for tEME and Gt-n-propanol.

Abstract

We report on the tentative detection of $trans$ Ethyl Methyl Ether (tEME), $t-CH_3CH_2OCH_3$, through the identification of a large number of rotational lines from each one of the spin states of the molecule towards Orion KL. We also search for $gauche$-$trans$-n-propanol, $Gt-n-CH_3CH_2CH_2OH$, an isomer of tEME in the same source. We have identified lines of both species in the IRAM 30m line survey and in the ALMA Science Verification data. We have obtained ALMA maps to establish the spatial distribution of these species. Whereas tEME mainly arises from the compact ridge component of Orion, Gt-n-propanol appears at the emission peak of ethanol (south hot core). The derived column densities of these species at the location of their emission peaks are $\leq(4.0\pm0.8)\times10^{15} cm^{-2}$ and $\leq(1.0\pm0.2)\times10^{15} cm^{-2}$ for tEME and Gt-n-propanol, respectively. The rotational temperature is $\sim100 K$ for both molecules. We also provide maps of $CH_3OCOH$, $CH_3CH_2OCOH$, $CH_3OCH_3$, $CH_3OH$, and $CH_3CH_2OH$ to compare the distribution of these organic saturated O-bearing species containing methyl and ethyl groups in this region. Abundance ratios of related species and upper limits to the abundances of non-detected ethers are provided. We derive an abundance ratio $N(CH_3OCH_3)/N(tEME)\geq150$ in the compact ridge of Orion.