Submillimeter observations of Arp220 and the expanded Sub-Millimeter 
Array

In the talk I will present the first interferometric submillimeter 
observations of Arp220 taken with the CSO-JCMT interferometer 
on Mauna Kea. Since mapping is not possible with a single baseline 
interferometers, models were fitted to the visibilities, suggesting 
that CO 3-2 emission roughly corresponds to the CO 2-1 emission,
and thus indicating that the 2 emission sources of Arp220 have 
similar temperatures.  HCN single dish observations, however, 
suggest that the nuclei are at different densities and are consistent with
the hypothesis that they are at different stages of a starburst. 

More baselines are required to map objects such as Arp220.
The extended Sub-Millimeter Array (eSMA), an interferometer consisting of
the CSO, JCMT and the SMA,  will be perfectly suited for this task. In the
second part of the talk I will describe the technical requirements for the
eSMA and introduce the necessary instrumental changes. In 2005, forty
two days are already set aside for eSMA operation, which will allow 
us to take submillimeter images with high resolution and high sensitivity.