Title: Dust and High Excitation Lines in Arp 220 at 0.25 - 0.5 '''' res.

Abstract:
I will present sub-arcsec imaging with ALMA of the dust continuum and HCN line emission in 
Bands 7 and 9 in the ULIRG Arp 220. These results indicate gas masses of ~2 billion solar 
masses on each nucleus, confined to radii ~25-50 pc. The mean gas densities are 10^5 cm^-3. 
The CO conversion factor is evaluated using the dust continuum and dynamical mass 
constraints. I also speculate on the nature of the gas structures there.