CO Depletion and Deuterium Fractionation in Barnard 5

In this work, we investigate how deuterium fractionation correlates with CO depletion factor in the Barnard 5 filament in the low-mass star formation region of the Perseus molecular cloud. Reactions of deuteration start in the gas phase, and CO concentration in the gas affects the rate of these reactions. The lines N2H+(1-0), N2D+(1-0), H13CO+(1-0), DCO+(2- 1), and C18O(2-1) were observed with the IRAM-30m telescope. The column densities were calculated from the observation maps. The maps of the deuterium fraction N2D+/N2H+ , DCO+/HCO+ , and CO depletion factor were plotted to analyse their distribution in the filament. Based on the distributions of the deuterium fraction and CO depletion factor, we conclude that the deuterium fraction increases with CO depletion in nitrogen-bearing species by more than a factor of 2. The deuterium fraction of DCO+/HCO+ increases by a factor of 2 along the direction from the protostar to the cold dense core.