ALMA observations of doubly deuterated water: inheritance of water from the prestellar environment

Establishing the origin of water D/H ratio in Solar System is central to our understanding chemical trail during star and planet formation process. Recent modeling suggests that comparisons D$_2$O/HDO HDO/H$_2$O ratios are a powerful way trace evolution and, particular, determine whether inherited from molecular cloud or established locally. We seek D$_2$O column density derive warm region toward low-mass Class 0 sources B335 L483. The results compared with astrochemical models previous observations their implications for water. present ALMA transition at 316.8 GHz L483 $<$0.5" ($<$ 100 au) resolution, probing inner envelope gas. densities D$_2$O, HDO, H$_{2}^{18}$O determined by synthetic spectrum direct Gaussian fitting, under assumption single excitation temperature similar spatial extent three isotopologs. detected both envelope. derived $(1.0\pm0.2)\times10^{-2}$ $(1.4\pm0.1)\times10^{-2}$ B335. high strong indication inheritance prestellar phase down This implies local conditions phase, such as temperatures timescales, chemistry later stages could provide source differentiation young systems. In addition, observed D$_2$O/H$_2$O support an dichotomy deuterium fractionation isolated clustered protostars, namely, higher