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

摘要

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 vD,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 JN = 43-32 line of CCS. From our N2H+ observations, the fractional abundance of the molecular nitrogen N2 is found to be 7 × 10-5, consistent with all the nitrogen being in molecular form and not depleted onto dust grains.