2017MNRAS.467L..61G

Extremely high velocity emission, likely related to jets, is known to occur in some protoplanetary nebulae. However, the molecular complexity of this kinematic component is largely unknown. We observed the known extreme outflow from the protoplanetary nebula IRAS 16342-3814, a prototype water fountain, over the full frequency range from 73-111 GHz with the Redshift Search Receiver (RSR) on the Large Millimetre Telescope. We detected the molecules SiO, HCN, SO and ¹³CO. All molecular transitions, with the exception of the latter, are detected for the first time in this source and all present emission with velocities up to a few hundred km/s. IRAS 16342-3814 is therefore the only source of this kind presenting extreme outflow activity in all these molecules simultaneously, with SO and SiO emission showing the highest velocities found for these species in protoplanetary nebulae. A tentative weak SO component with a full width at half-maximum of ∼700 km/s remains to be confirmed. The extreme outflow gas consists of dense gas (n_ H₂ > 10^4.8-10^5.7 cm^–3) with a mass larger than ∼ 0.02-0.15 M_☉. The relatively high abundances of SiO and SO may be an indication of oxygen-rich extremely high velocity gas.