Dense cores in Perseus molecular cloud

Our detection rate of N_2_H^+^ is 62%, rising to 84% for SCUBA-selected targets. In agreement with previous observations, we find that the dense N_2_H^+^ targets tend to display nearly thermal line widths, particularly those that appear to be starless (using Spitzer data), indicating that turbulent support on the small scales of molecular clouds is minimal.

For those N_2_H^+^ targets that have an associated SCUBA dense core, we find that their internal motions are more than sufficient to provide support against the gravitational force on the cores.