Student Barry O'Connell continued to investigate the nature of the outflows from the youngest protostars. Detailed near-infrared data for three outflows have been obtained and are being analysed. All three show a curious arrangement of shock waves. The shock physics has been investigated by studying the spatial distributions of excitation and radial velocity. With supervisor Michael Smith and several external collaborators including Tom Ray and Dirk Froebrich (DIAS, Dublin), he has found that magnetohydrodynamic bow shocks in which the magnetic field plays a key role are essential. Each outflow is unique and our overall understanding remains quite superficial.
Shock waves accelerate, heat and destroy material in their paths. In astronomy, shock waves are ubiquitous. The fact that a shock front heats the gas makes it a strong radiator and hence a focus for our attention. Student Babulakshmanan Ramachandran began a general study of shock waves in astrophysics. With Michael Smith, he generalised the equations for disturbed shock waves to see if they move steadily or if they are unstable. He took a general specific heat ratio and thus compared the linear stability criteria for atomic and molecular shocks. The regime in which molecular shocks suffer overstability (growing oscillations) was found to be quite restricted. However, low-amplitude high-frequency oscillations are expected under a wide range of conditions.