A CSO Search for $l$-C$_3$H$^+$: Detection in the Orion Bar PDR

TL;DR

This study reports the detection of l-C3H+ in the Orion Bar PDR using CSO, providing insights into its abundance and excitation, and guiding future observational efforts for this molecule.

Contribution

First detection of l-C3H+ in the Orion Bar PDR, expanding knowledge of its distribution and physical conditions in interstellar environments.

Findings

Detection of l-C3H+ in Orion Bar PDR with specific temperature and column density.

Non-detections in 38 other sources with upper limits on abundance.

Guidance for future searches of l-C3H+ in space.

Abstract

The results of a Caltech Submillimeter Observatory (CSO) search for $l$-C$_3$H$^+$, first detected by Pety et al. (2012) in observations toward the Horsehead photodissociation region (PDR), are presented. A total of 39 sources were observed in the 1 mm window. Evidence of emission from $l$-C$_3$H$^+$ is found in only a single source - the Orion Bar PDR region, which shows a rotational temperature of 178(13) K and a column density of 7(2) x $10^{11}$ cm$^{-2}$. In the remaining sources, upper limits of ~10$^{11} - 10^{13}$ cm$^{-2}$ are found. These results are discussed in the context of guiding future observational searches for this species.