Organic molecules in the hot corinos and circumstellar disks of IRAS 16293-2422

Abstract Using the recently commissioned Submillimeter Array (SMA), we have detected several complex organic molecules, including (CH 3 ) 2 O, C 2 H 5 OH, C 2 H 5 CN, and tentatively CH 2 CDCN, toward the protostellar hot cores of IRAS 16293-2422 at arcsecond-resolution (≲400 AU in radius). Vibrationally excited transitions of SO, SO 2 and HCN with energy levels up to 1800 K were also observed. In addition to the other organic molecules (HC 3 N, CH 2 CO, CH 3 OH, CH 2 CHCN and HCOOCH 3 ) previously reported by us (Kuan, Y.-J., Huang, H.-C., Charnley, S.B., Hirano, H., Takakuwa, S., et al. Organic molecules in low-mass protostellar hot cores: submillimeter imaging of IRAS 16293-2422. Astrophys. J. 616, L27–L30, 2004) these results clearly indicate the existence of a rich organic chemistry in low-mass ‘hot corinos’. From the observation of optically thin HC 15 N emission, we conclude I16293A is a rotating circumstellar disk lying along the north–south direction ∼10° to the east and with an inclination ∼30° to the sky. We suggest that the observed vibrational SO and SO 2 emission may originate from shock waves near or in the circumstellar disks. Between the two cores, we find a strong anticorrelation in emission from C 2 H 5 OH and C 2 H 5 CN. The relative contribution of gas phase and grain-surface chemistries to the production of the observed complex molecules is discussed. We point out the shortcomings underlying recent claims that all the O-bearing organics are formed on grains. The presence of so many well-known interstellar molecules in solar-type hot corinos strengthens the link between molecular cloud chemistry, the starting materials of protoplanetary disks such as the protosolar nebula, and the composition of comets. Establishing the fine details of this connection is crucial in answering fundamental questions concerning the importance of galactic astrochemistry for astrobiology.