RSAA Colloquia / Seminars / Feast-of-Facts: Friday, 21 April 2017, 14:00-14:20; Duffield Lecture Theatre

Laurie Chu

"Ice Feature Spectroscopy in Nearby Molecular Cores With JWST NIRCam"

Molecular clouds show the earliest stages of stellar and planetary evolution and provide an opportunity to understand how grains grow to form planetary bodies. In molecular clouds with a total visual extinction above a few magnitudes, some components of the molecular gas freeze out on the surfaces of dust grains. These ice mantles around dust grains are the sites of complex surface chemistry that leads to the formation of simple organic molecules in these mantles. The icy surfaces also facilitate the coagulation of the dust particles, setting the stage for grain growth and ultimately the formation of planetary bodies. As part of the JWST NIRCam GTO program, we will observe a selection of small molecular cores using the wide field grism spectroscopy mode of NIRCam. I will present the results of a preliminary study of several candidate molecular cores using UKIRT, Spitzer, and IRTF. After the preliminary studies we have selected three molecular cores in different evolutionary stages for the GTO program: B68, a quiescent molecular core, LDN 694-2, a collapsing pre-stellar core, and B335, a protostellar core. All these cores are seen against a dense background of stars in the inner Galaxy and offer the opportunity for spatially well-resolved mapping of the ice feature distribution. We will obtain slitless grism spectroscopy with NIRCam in six filters covering the features of H2O, CO2, CO, CH3OH, and the XCN feature. Simulations using aXeSim have shown that spectrum overlap will occur in a fraction of the spectra, but will not be a prohibitive problem.