SIMBAD references

High spatial-resolution observations of the protoplanetary nebula CRL2688 were made by the CS J=1-0 and J=2-1 lines with the Nobeyama Millimeter Array with angular resolutions of 6"x6" and 3"x3", respectively. The mapping observations reveal that strong CS peaks in the J=2-1 line are located symmetrically at both sides of the optical dark lane at the center, though the CS J=1-0 distribution is rather round. These CS peaks seem to be slightly misaligned from the optical bipolar axis. A modeling of the CRL 2688 envelope results that the density distribution is nearly spherically symmetric but the abundance of CS is enhanced near the polar regions. The increase of the CS abundance near the poles can be explained by the chemistry of sulfur containing molecules in the postshocked region in the high-velocity flow.