Detailed Structure of Low‐Density Molecular Gas in High‐Latitude Clouds

Abstract

Extensive strip-scan observations of three high-latitude clouds— MBM 32, MBM 54, and MBM 55—were carried out in 12CO 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 ~0.2 pc down to ~0.02 pc. Most of them have low gas density (≲102 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.