Herschel observations of EXtra-Ordinary Sources: The Terahertz spectrum of Orion KL seen at high spectral resolution

TL;DR

This paper reports high spectral resolution observations of Orion KL in the terahertz range using Herschel, revealing detailed emission line characteristics and the impact of frequency on line density.

Contribution

First high spectral resolution measurements of Orion KL in the terahertz range, providing new insights into its molecular emission components.

Findings

Emission lines primarily from Orion KL's hot core and outflows

Line density decreases at higher frequencies compared to lower bands

Widespread emission from H2O, SO2, and OH

Abstract

We present the first high spectral resolution observations of Orion KL in the frequency ranges 1573.4 - 1702.8 GHz (band 6b) and 1788.4 - 1906.8 GHz (band 7b) obtained using the HIFI instrument on board the Herschel Space Observatory. We characterize the main emission lines found in the spectrum, which primarily arise from a range of components associated with Orion KL including the hot core, but also see widespread emission from components associated with molecular outflows traced by H2O, SO2, and OH. We find that the density of observed emission lines is significantly diminished in these bands compared to lower frequency Herschel/HIFI bands.