Evidence for shocked interstellar gas toward the Perseus OB2 association

Optical measurements of absorption lines of CH+ and CH toward zeta, omicron, and xi Persei reveal a shift in velocity between the two molecular species. The equivalent width of the CH+ varies directly with both the amount of shift seen and the line width. The present observations confirm predictions of the chemical model formulated by Elitzur and Watson. The model requires shocks for producing sufficient amounts of CH+; therefore, strong evidence for shocked interstellar gas is now available. Reexamination of the optical results for OH toward zeta and omicron Persei indicates that a substantial fraction of the OH also was formed in the high-temperature shocked gas