Speaker
Gan Luo
(IRAM)
Description
We report the first detection of DCN in a low-density translucent sightline ($n_{H_2}$~390 cm$^{-3}$, Av~0.85 mag) through sensitive absorption-line observations with NOEMA. The observed DCN/HCN ratio is two orders of magnitude higher than the elemental deuterium-to-hydrogen abundance ratio (D/H~10$^{-5}$), challenging predictions from current chemical models. This discrepancy suggests a significant and unexpected boost in deuterium fractionation under low-density conditions. To reconcile this result, we propose that the observed cloud may represent a dispersal phase of a previously denser core, where the gas density in its evolutionary history must have exceeded 10$^{3.5}$ cm$^{-3}$.
Primary author
Gan Luo
(IRAM)
Co-authors
Prof.
Di Li
(Tsinghua University)
Prof.
Serena Viti
(Leiden)
Thomas Bisbas
(Zhejiang Lab)
Prof.
Zhiyu Zhang
(NJU)
