EPoS Contribution
EPoS Contribution
Extremely High Velocity (EHV) SiO components in young molecular outflows : A numerical perspective

Bhargav Vaidya
U Leeds, Leeds, UK
A bipolar, collimated outflow is one of the first signposts of star formation. As it propagates through the molecular cloud, it injects energy and momentum via shocks and fosters chemical evolution by forming, destroying and entraining molecules along its path. High velocity molecular outflows are extensively studied for both low-mass and high-mass stars. They are usually observed using standard outflow and shocks tracers like CO and SiO. However, the exact nature of the excitation of these molecules is not yet clear due to lack of models that simultaneously study the dynamics along with complex molecular chemistry. In this talk, I will present results from our recent Magneto-hydrodynamic (MHD) simulations of knotty jet propagation into a molecular cloud using the PLUTO code. The jet dynamical quantities evolve in conjunction with different non-equilibrium cooling prescriptions of varying complexities, including molecular cooling and hydrogen chemistry. The final state of the jet obtained is then given as an input to a 3D non-LTE radiative line transfer code to obtain SiO emission maps, spectra and position-velocity (PV) digrams. We find that EHV emission primarily comes from the interaction of internal knots with ambient molecular medium. Atacama Large Millimeter Array (ALMA) predictions based on our model (shown in the figure) can successfully explain various observational signatures of extremely high velocity (EHV) emission of SiO seen in early outflows. In particular, young internal knots show a distinct wedge like features in the PV diagram which are consistent with recent CO(1-0) observations of HH46/47 molecular outflow with ALMA. Further, our multi-line modeling of SiO supports the observational feature seen in Herbig-Haro (HH 211), in particular it reproduces line shapes and intensities for low and high SiO transitions and verify that higher line transitions trace regions closer to the axis of the jet.
Caption: Left: The integrated intensity map of SiO(2-1), (5-4) and (8-7). The emission map shows the J=5-4 line intensity (in units of Jy km/s/beam), the blue contours show the J=8-7 line intensity and the green contours show the J=2-1 line intensity. The jet is inclined at an angle of 60 degrees. Right: The PV diagram taken along the axis of the jet for the 5-4 line (in units of Jy/beam), showing the higher J transitions highlighting the knots of the jet and broad emission at the bow shock. In both panels the ticks on the color bar represent the different contour levels.
Collaborators:
T.A. Douglas, U Leeds
P. Caselli, U Leeds
Key publication

Suggested Sessions: Protostellar Outflows