Abstract
Deuterium fractionation is dependent on various physical and chemical parameters. Thus, the formation location and thermal history of material in the solar system is often studied by measuring its D/H ratio. This requires knowledge about the deuteration processes operating during the planet formation era. We aim to study these processes by radially resolving the DCN/HCN (at 0 3 resolution) and N2D+/N2H+ (∼0 3-0 9) column density ratios toward the five protoplanetary disks observed by the Molecules with ALMA at Planet-forming scales (MAPS) Large Program. DCN is detected in all five sources, with one newly reported detection. N2D+ is detected in four sources, two of which are newly reported detections. We derive column density profiles that allow us to study the spatial variation of the DCN/HCN and N2D+/N2H+ ratios at high resolution. DCN/HCN varies considerably for different parts of the disks, ranging from 10−3 to 10−1. In particular, the inner-disk regions generally show significantly lower HCN deuteration compared with the outer disk. In addition, our analysis confirms that two deuterium fractionation channels are active, which can alter the D/H ratio within the pool of organic molecules. N2D+ is found in the cold outer regions beyond ∼50 au, with N2D+/N2H+ ranging between 10−2 and 1 across the disk sample. This is consistent with the theoretical expectation that N2H+ deuteration proceeds via the low-temperature channel only. This paper is part of the MAPS special issue of the Astrophysical Journal Supplement.
Original language | English (US) |
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Article number | 10 |
Journal | Astrophysical Journal, Supplement Series |
Volume | 257 |
Issue number | 1 |
DOIs | |
State | Published - Nov 2021 |
All Science Journal Classification (ASJC) codes
- Astronomy and Astrophysics
- Space and Planetary Science