Deuterium chemistry in protoplanetary disks II The inner 30 AU

TL;DR

This study models deuterium chemistry in the inner 30 AU of protoplanetary disks, showing how physical conditions influence molecular abundances and D/H ratios, with implications for understanding comet compositions.

Contribution

It provides detailed chemical models of the inner disk regions, highlighting the impact of physical assumptions on molecular distributions and D/H ratios compared to previous models.

Findings

Good agreement with gas phase observations of non-deuterated species

Calculated D/H ratios in ices are higher than measured without additional processing

Physical condition variations significantly alter chemical abundance predictions

Abstract

We present the results of models of the chemistry, including deuterium, in the inner regions of protostellar disks. We find good agreement with recent gas phase observations of several (non--deuterated) species. We also compare our results with observations of comets and find that in the absence of other processing e.g. in the accretion shock at the surface of the disk, or by mixing in the disk, the calculated D/H ratios in ices are higher than measured and reflect the D/H ratio set in the molecular cloud phase. Our models give quite different abundances and molecular distributions to other inner disk models because of the differences in physical conditions in the model disk. This emphasizes how changes in the assumptions about the density and temperature distribution can radically affect the results of chemical models.