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.
