2006 Annual Science Report
University of Hawaii, Manoa Reporting | JUL 2005 – JUN 2006
Unveiling the Evolution and Interplay of Ice and Gas in Star-Forming Regions
It is generally thought that our Solar System formed in conditions similar to current on-going low mass star forming systems seen throughout our Galaxy. Initially, a dense core (within a molecular cloud) slowly contracts due to loss of supporting forces such as magnetic fields. This results in the formation of a central object – the Young Stellar Object (YSO)- surrounded by a protoplanetary disk. At this stage the mass of the central YSO is less than the surrounding envelope mass and accretion of material on to the newly forming star is vigorous. At this point the central star is deeply embedded in the natal cloud and can only be studied through the use of sub-millimeter and infrared telescopes. Due to rotation, the disk grows around the protostar and a strong outflow, perpendicular to the disk, is generated. As the outflow begins to dominate, bipolar jets expand outwards and shock the surrounding material. Eventually, a significant fraction of the surrounding molecular envelope is blown away and it is at this stage that newly formed star (and planetary system) become visible.
Paralleling this dynamical evolution are vigorous chemical changes in the ice, gas, and dust associated with the circumstellar envelope. When observed in the sub-millimeter a rich shock induced chemistry is seen, in particular sulphur bearing compounds. The corresponding IR spectrum reveals a wealth of ice mantles in the cold natal molecular cloud. When the in-fall and outflows abate, a hot core phase is reached in which the evaporation of ice-mantles gives rise to a gas-phase chemistry that involves complex and large molecules. This processed dust, ice and gas then become the building blocks for planets, asteroids and comets.
Through the combined use of ground- and space-based telescopes, we intend to measure the composition and evolution of the ice and gas in star-forming regions similar to our early solar nebula. Observations of the state of the ice and gas, at both infrared and sub-millimeter wavelengths, will reveal vital information on the chemical and physical conditions of the protostellar envelope during the star formation process. The chemical makeup and inventory of the ice and gas will be inter- and intra-compared in order to determine the evolutionary relationship between these two reservoirs. The molecules directly observed in the ice and gas will promote the formation of chemical evolutionary diagnostic diagrams. These diagnostic tools will allow us to determine the degree of processing that the ice experiences in the star formation process and help us understand the true nature/composition of ice and organics likely delivered to the early solar system.