Molecular gas in S106: Morphology, kinematics, and chemistry of a star-forming region

The biconical H II region S106 is a site of recent star formation; it consists of two ionized lobes flowing out from a central disk of cold molecular gas in which is embedded the newly formed massive star IRS 4. This entire complex is still embedded in the molecular cloud from which it formed.I have found that the central disk is expanding at 2 km s$\sp{-1}$ and that clumps of molecular material are being ablated from its surface by the ionized outflow and accelerated to higher velocities. The ring is not rotating and may be supported by magnetic field pressure or the pressure of the ionized outflow. The origin and initial collimation of the ionized outflow remains unclear but must be occurring relatively near IRS 4. I argue that for distances from IRS 4 larger than 5", the kinematics of the outflow is dominated by the pressure of the magnetic field. The magnetic field at the interface between the molecular gas and ionized outflow is very large, on the order of 1 mG. Finally, I show that there is a clear chemical evolution through the shock front between the ionized and molecular gas, with the HCO$\sp+$/CS ratio being greatly enhanced at the interface. Theoretical models are still much too crude to adequately explore the chemistry which occurs in a magnetic shock. Finally, I found that at long wavelengths, the spectral index of the continuum radiation becomes quite large, suggesting that at these wavelengths the emission is dominated by synchrotron radiation. Such emission requires both magnetic fields and relativistic electrons, which might be supplied in S106 by the first order Fermi effect in the shock region.U of I OnlyETDs are only available to UIUC Users without author permissio