IGPP Seminar Series

Insights on the Origins of Solar System Isotopic Ratios Using Protostellar Observations and Radiative Transfer Modeling

by Rachel Smith
UCLA, IGPP

Abstract

New high-resolution observations of CO isotopologues toward young stellar objects (YSOs) and molecular clouds obtained with the CRIRES spectrograph (VLT) reveal 12CO/13CO ratios ranging from ~ 84 - 160. The majority of these ratios are significantly higher than those assumed for the local interstellar medium (ISM; ~ 69) and the Solar system (~ 89). To date, our observations include several embedded YSOs, protostellar disks, and foreground clouds, and provide important observational constraints toward understanding the isotopic evolution of the early Solar system. We show that YSOs may not be isotopically similar to their parent clouds, suggesting that Galactic chemical evolution models may be insufficient in describing the apparent discrepancy in 12C/13C between the Solar system and local ISM. Furthermore, cloud isotopic heterogeneity may be an important factor toward understanding protostellar evolution. Our analyses show that while CO self-shielding may explain the high 16O/18O and 16O/17O ratios observed in several objects, it apparently does not explain the trends we find in the carbon isotopes. Initial results comparing CO column densities between the ice and gas phases for these embedded objects indicate that high 12CO/13CO ratios in protostellar gas may be achievable via a Rayleigh fractionation process.
Tuesday, 25 May 2010
3853 Slichter Hall
Refreshments at 3:45 PM
Lecture at 4:00 PM