Dense Cores in Dark Clouds. XI. A Survey for N2H+, C3H2, and CCS

We have used the 3 mm receiver and upgraded antenna of Haystack Observatory to make high spatial and spectral resolution observations of lines of N 2 H + and C 3 H 2 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 = 4 3 -3 2 line of CCS. From our N 2 H + observations, the fractional abundance of the molecular nitrogen N 2 is found to be ≃7 × 10 -5 , consistent with all the nitrogen being in molecular form and not depleted onto dust grains.