Organic Molecules in the Hot Corinos and Circumstellar Disks of IRAS 16293-2422

Astrophysics, abstract
astro-ph/0504271

From: Hui-Chun Huang [view email]

Date: Tue, 12 Apr 2005 14:06:20 GMT   (239kb)

Using the recently-commissioned Submillimeter Array (SMA), we have detected
several complex organic molecules, including (CH3)2O, C2H5OH, C2H5CN, and
tentatively CH2CDCN, toward the protostellar hot cores of IRAS 16293-2422 at
arcsecond-resolution (~< 400 AU in radius). Vibrationally excited transitions
of SO, SO2 and HCN with energy levels up to 1800 K were also observed. In
addition to the other organic molecules (HC3N, CH2CO, CH3OH, CH2CHCN and
HCOOCH3) previously reported by us (Kuan et al. 2004), these results clearly
indicate the existence of a rich organic chemistry in low-mass `hot corinos’.

From the observation of optically thin HC15N emission, we conclude I16293A is
a rotating circumstellar disk lying along the north-south direction ~10 deg to
the east and with an inclination ~30 deg to the sky. We suggest that the
observed vibrational SO and SO2 emission may originate from shock waves near or
in the circumstellar disks. Between the two cores, we find a strong
anticorrelation in emission from C2H5OH and C2H5CN. 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.

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