VELOCITY SHIFTS IN L1228 - THE DISRUPTION OF A CORE BY AN OUTFLOW

We present (CO)-C-12(1-0), (CO)-C-13(1-0), CS(2-1), and C3H2(2(12)-1(0 1)) observations of the L1228 outflow and dense core with resolutions between 50 '' and 25 ''. The bipolar molecular outflow originates from IRAS 20582+7724 and extends over almost 15' (approximate to 1.2 pc). It has a well-collimated blue lobe and less collimated red lobe, which is split into two branches that diverge from the IRAS position. The t wo CO outflow lobes are well aligned with previously observed high-exc itation emission from H-2 and H alpha, although these emissions presen t bendings from a straight line, suggesting that the outflow driving w ind changes direction by interacting with the ambient cloud. The dense gas in the core also shows evidence for acceleration in the outflow d irection, although its velocity is significantly lower than that of th e CO emission. The dense gas acceleration appears in the CS and C3H2 s pectra as velocity shifts in the line centroid on the order of one C3H 2 full line width (approximate to 0.4 km s(-1)). These shifted line pr ofiles are not accompanied by any significant emission at ambient core velocities. Furthermore, there is very little or no quiescent C3H2 em ission toward the outflow lobes, as if the outflow acceleration had be en so efficient that all the dense gas has been set into motion. This acceleration, in addition, has occurred without appreciable line width enhancement, suggesting that it has not increased substantially the t urbulence of the gas. From the large size of the velocity shifts (comp arable to the gas escape velocity) and from our energetics estimates, we infer that the L1228 outflow could significantly disperse the dense gas in the core by the time the outflow phase ends.