My PhD thesis involved studying the role of protostellar outflows in star formation feedback. When young stars form, they accrete material from their parent molecular cloud. This material falls from the surrounding envelope onto an accretion disk and then is magnetically funneled onto the star. Due to a complex magneto hydrodynamic (MHD) process that is not yet fully understood, a portion of this material is launched from the poles of the star in a high speed (~100 - 500 km/s) collimated jet.
This high velocity jet slams into the surrounding molecular cloud, depositing energy and momentum. These shocks excite the atoms and molecules in the molecular material and are seen as emission line nebulae also known as Herbig-Haro (HH) objects. I am using these HH objects as a tracer of momentum deposition in the cloud.
Star formation is a dynamic process whereby the outflows and radiation from young stars impact the dynamics of the parent cloud and affect the formation of subsequent generations of stars. In giant molecular clouds (GMCs) which form high mass stars, the interaction between the stars and the cloud is dominated by these high mass stars. Specifically the expansion of HII regions formed by the ionizing radiation from the massive stars and the shock waves from supernovae when they die are probably far more damaging to the cloud than protostellar outflows. In lower mass clouds, however, where no massive stars form, what generates the turbulence in the molecular material? Is that turbulence constantly driven or does it decay rapidly? If it is driven, then perhaps protostellar outflows are the driving force. The aim of my thesis is to determine the role of protostellar outflows in the driving of turbulence in molecular clouds.
Our primary tools in this study are large area imaging surveys of molecular clouds in narrowband filters which we use to identify and count the HH objects which trace the interaction between the protostellar jet and the cloud. By measuring the frequency and area covering factor of these shocks we can get a rough measure of the momentum injected by shocks.
Primarily we've used the Mosaic cameras on the 4 meter Mayall telescope at Kitt Peak in Arizona and the 4 meter Blanco telescope at Cerro Tololo in Chile with additional data collected at the WIYN 0.9 meter telescope at Kitt Peak and the 3.5 meter ARC telescope at Apache Point. Subsequent to my thesis work, I’ve now also used the United Kingdom Infrared Telescope (UKIRT) and the Canada-France-Hawaii Telescope (CFHT) to push the surveys in to the near infrared. Also, I’ve used data from the Subaru Telescope for very deep imaging of some of these flows.
The primary region which I've studied in detail is the Perseus Molecular Cloud. Perseus is relatively close (~300 pc or ~1000 light years distant) and is comparatively low mass (~10,000 solar masses). Perseus has no recently formed massive stars to produce large HII regions and so it is an ideal region to study the effect of protostellar outflows.
