Paper detail

A young bipolar outflow from IRAS 15398-3359

Changing physical conditions in the vicinity of protostars allow for a rich and interesting chemistry to occur. Heating and cooling of the gas allows molecules to be released from and frozen out on dust grains. These changes in physics, traced by chemistry, as well as the kinematical information allows us to distinguish between different scenarios describing the infall of matter and the launching of molecular outflows and jets. We aim at determining the spatial distribution of different species, of different chemical origin. This is to examine the physical processes in play in the observed region. From the kinematical information of the emission lines we aim at determining the nature of the infalling and outflowing gas in the system. We also aim at determining the physical properties of the outflow. Maps from the Sub-Millimeter Array reveal the spatial distribution of the gaseous emission toward IRAS15398-3359. The line radiative transfer code LIME is used to construct a full 3D model of the system taking all relevant components and scales into account. CO, HCO+ and N2H+ are detected and are shown to trace the motions of the outflow. For CO, also the circumstellar envelope and the surrounding cloud have a profound impact on the observed line profiles. N2H+ is detected in the outflow, but is suppressed towards the central region, perhaps due to the competing reaction between CO and H3+ in the densest regions as well as destruction of N2H+ by CO. N2D+ is detected in a ridge south-west from the protostellar condensation. The morphology and kinematics of the CO emission suggests that the source is younger than 1000 years. The mass, momentum, momentum rate, mechanical luminosity, kinetic energy and mass-loss rate are also all estimated to be low. A full 3D radiative transfer model of the system can explain all the kinematical and morphological features in the system.