The environments where stars are born contain gas and dust grains covered by icy mantles. As the star forms and heats up its surroundings, the ices evaporate which leads to a very complex chemistry with high abundances of deuterated molecules. While formaldehyde and water are both ice constituents, deuterated formaldehyde is very abundant in comets and star forming regions, while deuterated water rarely is. Here, we explain this selective deuteration by following the formation and evolution of the ices as a cloud collapses to form a star. We show that the deuteration of formaldehyde is sensitive to the gas D/H ratio as the cloud undergoes gravitational collapse, while the deuteration of water strongly depends on the dust temperature at the time of ice formation.
| Comments: | 4 pages, 1 appendix, Submitted in A&A letter |
| Subjects: | Solar and Stellar Astrophysics (astro-ph.SR) |
| Cite as: | arXiv:1107.1984v1 [astro-ph.SR] |
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