We present resolved detections of DCO+, N2D+ and DCN towards the disk surrounding the Herbig Ae star HD 163296 using
ALMA.
Deuterated species have been detected in a handful of protoplanetary disks but the inheritance of the D/H ratio from early stages in the star
formation process to fully formed Solar System bodies remains unclear. In this talk, we spatially characterise the high and low temperature pathways
for the enhanced deuteration required to form these species. Using an estimate of the excitation of this molecules, we model the line emission of each
molecule in different radial zones with constant abundance. The DCO+ emission agrees well with a three-ring model with rings centered
at 70 AU, 160 AU and 260AU. The inner two rings roughly correspond to the DCN and N2D+ emission peaks and can be interpreted as
the regions where the high and low deuteration channels
dominate the formation of DCO+. We discuss several possible formation scenarios that can produce the third, outer ring of DCO+. We
also confirm previous estimates on the location of the CO snowline at 90 AU probed by N2D+. We conclude that the underlying radial
structure of DCO+ cannot
be fully understood with the current modest resolution but note the spatial scales of these features are similar to those seen in scattered light and
high resolution sub-millimeter continuum. Future high resolution observations and detailed chemical modelling will constrain the formation mechanism(s)
of DCO+ and the origin of the outer emission ring.
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