Discovery of an intriguing chemically rich outflow in the OMC-2/3 filament

ABSTRACT Studying chemically rich protostellar outflows and their jet provides an important insight into the low-mass star formation process and its related chemistry. While well-known shock tracers such as SiO can be used to study the jet properties and give information about the dynamics of the system, interstellar complex organic molecules (iCOMs) have been useful in constraining the age of shocked gas, for example. Yet, the number of outflows mapped in iCOMs is still limited. In this work, we study the outflow driven by the protostar FIR6c-a (HOPS 409) located in the OMC-2/3 filament. We report the detection of the red-shifted jet, left undetected in previous studies, as well as the detection of the iCOMs methanol (CH$_3$OH) and methyl cyanide (CH$_3$CN) for the first time towards this outflow. Using SiO, we derived some jet properties (i.e. collimation and dynamical time). We found a clear dichotomy between the blue- and red-shifted jets, likely due to the density of the medium in which the jets propagate. In addition, we identified two bow shocks within the blue-shifted part of the outflow, which we attribute to two different ejection events. Finally, using the CH$_{3}$OH and CH$_{3}$CN abundance ratio and chemical modelling, we constrained the outflow age to be $\ge 1000$ yr old and, surprisingly, found that a cosmic ray ionization rate of $10^{-14}$ s$^{-1}$ is needed to reproduce the observed ratio towards the source.