SOLIS XVII: Jet candidate unveiled in OMC-2 and its possible link to the enhanced cosmic-ray ionisation rate

TL;DR

This paper reports the discovery of a collimated jet near a protostar in OMC-2 FIR4, which may explain the observed high cosmic-ray ionisation rate through particle acceleration at the jet shock.

Contribution

It provides the first evidence linking a protostellar jet to enhanced cosmic-ray ionisation in a star-forming region.

Findings

Detection of a collimated jet near HOPS-108

Possible connection between jet activity and cosmic-ray ionisation

Physical-chemical modeling supports jet-driven particle acceleration

Abstract

The study of the early phases of star and planet formation is important to understand the physical and chemical history of stellar systems such as our own. In particular, protostars born in rich clusters are prototypes of the young Solar System. In the framework of the Seeds Of Life In Space (SOLIS) large observational project, the aim of the present work is to investigate the origin of the previously inferred high flux of energetic particles in the protocluster FIR4 of the Orion Molecular Cloud 2 (OMC-2), which appears asymmetric within the protocluster itself. Interferometric observations carried out with the IRAM NOEMA interferometer were used to map the silicon monoxide (SiO) emission around the FIR4 protocluster. Complementary archival data from the ALMA interferometer were also employed to help constrain excitation conditions. A physical-chemical model was implemented to characterise the particle acceleration along the protostellar jet candidate, along with a non-LTE analysis of the SiO emission along the jet. The emission morphology of the SiO rotational transitions hints for the first time at the presence of a collimated jet originating very close to the brightest protostar in the cluster, HOPS-108. The NOEMA observations unveiled a possible jet in the OMC-2 FIR4 protocluster propagating towards a previously measured enhanced cosmic-ray ionisation rate. This suggests that energetic particle acceleration by the jet shock close to the protostar might be at the origin of the enhanced cosmic-ray ionisation rate, as confirmed by modelling the protostellar jet.