A CSO search for l-C3H+: detection in the Orion Bar PDR

The results of a Caltech Submillimeter Observatory (CSO) search for l-C₃H⁺, first detected by Pety et al. in observations towards the Horsehead photodissociation region (PDR), are presented. A total of 39 sources were observed in the 1 mm window. Evidence of emission from l-C₃H⁺ 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) × 10¹¹ cm^-2. In the remaining sources, upper limits of ∼10¹¹-10¹³ cm^-2 are found. These results are discussed in the context of guiding future observational searches for this species.