Low-Frequency Carbon Recombination Lines in the Orion Molecular Cloud Complex

TL;DR

This study reports tentative detections of low-frequency carbon radio recombination lines in the Orion molecular cloud, providing insights into the transition of radiation mechanisms within its HII regions.

Contribution

First detection of low-frequency carbon recombination lines in Orion, revealing the transition from collisionally to radiatively pumped radiation mechanisms.

Findings

Detected alpha and beta transitions at 99-129 MHz

Locations coincide with infrared, optical, and radio emissions

Insights into radiation mechanism transition in HII regions

Abstract

We detail tentative detections of low-frequency carbon radio recombination lines from within the Orion molecular cloud complex observed at 99-129 MHz. These tentative detections include one alpha transition and one beta transition over three locations and are located within the diffuse regions of dust observed in the infrared at 100umm, the Halpha emission detected in the optical, and the synchrotron radiation observed in the radio. With these observations, we are able to study the radiation mechanism transition from collisionally pumped to radiatively pumped within the HII regions of the Orion molecular cloud complex.