Multiple Collimated Outflows in the Proto–Planetary Nebula GL 618

We present narrow-band H-alpha, [S II], and [O I] Hubble Space Telescopeimages of the young planetary nebula GL 618. This object is a compact, bipolarnebula that is currently undergoing the transition from asymptotic giant branchstar to planetary nebula. Our images confirm the presence of at least threehighly collimated outflows emanating from the central regions of GL 618. Wealso detect H-alpha emission close to the central dust lane and in an extendedscattered light halo. The three outflows are occurring simultaneously in thisobject, as opposed to being the result of a precessing jet. We derive aninclination for the brightest outflow in the East lobe of 39 degrees. Thisdiffers from the previous estimate of 45 degrees. In addition, our resultsindicate that the outflows seen in GL 618 are probably not coplanar. Linestrengths derived from the narrow-band images indicate a shock velocity in therange of 40 - 100 km/s. Based on the shock velocity we estimate that the age ofthe outflows is less than 500 years. The outflows seen in the optical images ofGL 618 are related to features seen in near-IR, CO and CS maps of this object.This relationship indicates that the outflows are playing a major role in themorphological evolution of this young planetary nebula, interacting with andshaping the neutral envelope surrounding GL 618. We discuss the implications ofthese jets and their interaction with the neutral envelope in the context ofcurrent models of planetary nebula formation.Comment: accepted for publication in Ap