Extinction Mapping of Pre-stellar Cores
Abstract
This project is aimed at studying the evolution of ice mantles on dust grains during the process of molecular core collapse and early protostellar evolution.
We will use the NIRCam grism mode to obtain spectra of background stars behind the target molecular cores in the wavelength range covering the absorption features of molecular cloud H2O, CH3OH, CO2 , XCN, and CO ices. In order to cover the full spectral range, we will use 6 different wide and medium filters in conjunction with the grism. We will obtain a few hundred spectra per target core, an order-of-magnitude improvement over existing studies. Our data will also contain regions of feature-free continuum extinction, which will allow to distinguish the effects of continuum extinction from ice feature absorption. These data will be the basis for future detailed comparisons with theoretical and laboratory models of ice mantle formation and grain surface chemistry. We will also obtain very deep continuum images with parallel observations with the short-wave channel of NIRCam for detailed mapping of the continuum extinction and studies of the core-shine in the target molecular cores. We are aware that the recommended procedure for NIRCam slitless spectroscopy is to use both grism orientations so that spectrum overlap can be resolved. For our project, using both grism orientations would exceed the allocated time. We have run simulation with axesim and actual deep images of our fields plus a model faint object distribution of the fraction of overlapping spectra, and are convinced that the better strategy for obtaining the maximum number of reducable spectra is to do deep observations in one grism orientation only. There will be a small fraction of spectra with unrecoverable spectrum overlap, but this loss is acceptable. Our goal is not completeness, but maximum source density.- Publication:
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JWST Proposal. Cycle 1
- Pub Date:
- June 2017
- Bibcode:
- 2017jwst.prop.1187H