The detection of a molecular bipolar flow in the multipolar planetary nebula NGC 2440

Abstract

We report the detection of a molecular bipolar outflow in the CO J = 3-2 line in the optical multipolar planetary nebula NGC 2440. The observed CO J = 3-2 emission shows two major velocity components which are blue- and redshifted by 18 km s -1 relative to the systemic velocity of PLSR = 43 km s -1. Both components are detected only near the central region and have a size of about 24″. In addition to this bulk motion, weak CO emissions in the central region are detected at higher velocities of ±20 to ±40 km s -1. The presence of the fast CO components are in line with the picture that the neutral dense torus is being torn apart by very fast outflowing winds. The spatial distribution of CO emission shows two emission peaks at the systemic velocity that are located 30″ to the northeast and 30″ to the south-west from the center in point symmetry. The positions of the two CO emission peaks coincide well with the emission knots in the optical, suggesting that the CO outflow corresponds to one pair of the multiple optical bipolar lobes of the nebula. This particular pair of bipolar lobes seem distinctly rich in heavy molecules compared with the other optical bipolar lobes. The extent of CO emission in NGC 2440 is well constrained. The total amount of CO molecules in NGC 2440 is 3.5 × 10 51 if the distance to NGC 2440 is 2.19 kpc and the excitation temperature is 25 K. © 2008. The American Astronomical Society. All rights reserved.