What:	An SMA View of Chemistry in Circumstellar Disks
Who:	Dr. Qi Chunhua
	(CfA, USA)
When:	Monday afternoon, Mar. 22th, 3:00 p.m
Where:	Room 327, Office Block, 2 West Beijing Road (PMO, CAS)
	Welcome to attend
	( PMO Academic committee & academic circulating committee)

　　   abstract　　　　　

　　　Millimeter-wave interferometers have imaged over a dozen molecular transitions in disks surrounding pre-main-sequence stars. These studies have improved our understanding of the physical and chemical structure of disks and provide insights into the complicated processes by which planetary systems form. As analogs to the Solar Nebula, these circumstellar disks offer a unique opportunity to study the conditions during the planet formation process, especially the complex chemical evolution that must occur.

　　  The SMA is an 8-element radio interferometer located atop Mauna Kea in Hawaii. Operating at frequencies from 180 GHz to 700 GHz, the 6m dishes may be arranged into configurations with baselines as long as 509m, producing a synthesized beam of sub-arcsecond width. The SMA is playing a leading role in providing data to characterize the physical and chemical properties of the disks around young low-mass stars. I will present high resolution (0.5" to 5") SMA observations of 12CO, 13CO, C18O, HCO+, DCO+, CN, HCN, DCN and H2CO towards disks around TW Hya and several other T Tauri and Herbig Ae stars. These results have been compared with detailed chemical models to investigate the influence of the gas temperature structure, grain growth, and stellar X-ray/FUV emission on the radial and vertical distribution of the molecular abundances in disks. I will also briefly present some results from DISCS, an SMA legacy program "Protoplanetary Disk Imaging Survey of Chemistry with SMA", aimed at surveying the chemical composition of protoplanetary disks.