SIMBAD references

We have used the 3 mm receiver and upgraded antenna of Haystack Observatory to make high spatial and spectral resolution observations of lines of N₂H⁺ and C₃H₂ in 60 dense cores. Both species are detected in most of the cores, and the velocities, and line widths are well correlated. This suggests that ions and neutrals are well coupled. We found v_D,max_ ≤ 0.03 km.s^–1, which is the first observational constraint on the relative speed of ions and neutrals in star-forming dense cores. Twenty of the cores were also observed in the J_N = 4₃-3₂ line of CCS. From our N₂H⁺ observations, the fractional abundance of the molecular nitrogen N₂ is found to be ≃7x10^–5, consistent with all the nitrogen being in molecular form and not depleted onto dust grains.