Detailed structure of low-density molecular gas in high-latitude clouds

Extensive strip-scan observations of three high-latitude clouds- MBM 32, MBM 54, and MBM 55- were carried out in (CO)-C-12 J = 1-0 emission with an angular resolution of 15, or 0.0072 pc (1500 AU) at 100 pc. We resolved clumps with sizes from similar to0.2 pc down to similar to0.02 pc. Most of them have low gas density (less than or similar to10(2) cm(-3)) and sizes significantly smaller than their corresponding Jeans lengths. Some of them are well-isolated from the rest of the molecular components, suggesting their (quasi-) stable dynamical state. They provide a clear case for structure formation not caused by gravitational contraction and are most likely formed through thermal instability in interstellar shocks. We unexpectedly discovered in the position-velocity diagrams a number of localized velocity shifts. Their typical size is 0.05 pc, and some of them exhibit a velocity gradient of similar to40 km s(-1) pc(-1), which is among the largest ever observed in non-star-forming clouds. None of them have young stellar objects in their vicinity. Contraction of shock-compressed gas may produce rapidly rotating/contracting, but apparently unbound, clumps. These features may provide more evidence for structure formation through thermal instability of shocked gas.