Solis IV. Hydrocarbons in the OMC–2 Fir 4 Region, a Probe of Energetic Particle Irradiation of the Region (original) (raw)

We report new interferometric images of cyclopropenylidene, c–C 3 H 2 , towards the young protocluster OMC–2 FIR 4. The observations were performed at 82 and 85 GHz with the NOrthern Extended Millimeter Array (NOEMA) as part of the project Seeds Of Life In Space (SOLIS). In addition, IRAM-30m data observations were used to investigate the physical structure of OMC–2 FIR 4. We find that the c–C 3 H 2 gas emits from the same region where previous SOLIS observations showed bright HC 5 N emission. From a non-LTE analysis of the IRAM-30m data, the c–C 3 H 2 gas has an average temperature of ∼40 K, a H 2 density of ∼3×10 5 cm −3 , and a c–C 3 H 2 abundance relative to H 2 of (7±1)×10 −12. In addition, the NOEMA observations provide no sign of significant c–C 3 H 2 excitation temperature gradients across the region (about 3-4 beams), with T ex in the range 8±3 up to 16±7 K. We thus infer that our observations are inconsistent with a physical interaction of the OMC–2 FIR 4 envelope with the...