Vol. 587
In section 6. Interstellar and circumstellar matter

Deuterium fractionation in the Ophiuchus molecular cloud

The authors use several transitions of N_2H and N_2D, along with optically thin 17CO transitions, in a very careful study of the deuterated fraction, CO depletion factors, and internal dynamics over a wider range of starless cores in the dark cloud L1668. They show that the more highly deuterated cores are also more quiescent; most of the CO lines are supersonic, while most N_2H lines are subsonic. They suggest that these quiescent pre-star forming cores may be an initiating stage in cloud evolution without the densest cores. The paper also importantly indicates what the ALMA high spatial resolution will be able to test beyond these few molecular probes.