Interaction of supernova remnants with interstellar clouds: From the nova laser to the galaxy

The interaction of strong shock waves, such as those generated by the explosion of supernovae with interstellar clouds, is a problem of fundamental importance in understanding the evolution and the dynamics of the interstellar medium (ISM) as it is disrupted by shock waves. The physics of this essential interaction sheds light on several key questions: (1) What is the rate and total amount of gas stripped from the cloud, and what are the mechanisms responsible? (2) What is the rate of momentum transfer to the cloud? (3) What is the appearance of the shocked cloud, its morphology and velocity dispersion? (4) What is the role of vortex dynamics on the evolution of the cloud? (5) Can the interaction result in the formation of a new generation of stars? To address these questions, one of us has embarked on a comprehensive multidimensional numerical study of the shock cloud problem using high-resolution adaptive mesh refinement (AMR) hydrodynamics. Here we present the results of a series of Nova laser experiments investigating the evolution of a high-density sphere embedded in a low-density medium after the passage of a strong shock, wave, thereby emulating the supernova shock-cloud interaction. The Nova laser was utilized to generate a strong (similar to Mach 10) shock wave which traveled along a miniature beryllium shock tube, 750 mu m in diameter, filled with a low-density plastic emulating the ISM. Embedded in the plastic was a copper microsphere (100 mu m in diameter) emulating the interstellar cloud. Its morphology and evolution as well as the shock wave trajectory were diagnosed via side-on radiography. We describe here experimental results of this interaction for the first time out to several cloud crushing times and compare them to detailed two- and three-dimensional radiation hydrodynamic simulations using both arbitrary Lagrangian and Eulerian hydrodynamics (ALE) as well as high-resolution AMR hydrodynamics. We briefly discuss the key hydrodynamic instabilities instrumental in destroying the cloud and show the importance of inherently three-dimensional instabilities and their role in cloud evolution. We describe the relationship of these new experiments and calculations to recent ROSAT X-ray observations in the Cygnus Loop.