We survey the kinematics of over one hundred and fifty candidate ( and potentially star-forming ) dense cores in the Perseus molecular cloud with pointed N _ { 2 } H ^ { + } ( 1-0 ) and simultaneous C ^ { 18 } O ( 2-1 ) observations .
Our detection rate of N _ { 2 } H ^ { + } is 62 % , rising to 84 % for JCMT SCUBA-selected targets .
In agreement with previous observations , we find that the dense N _ { 2 } H ^ { + } targets tend to display nearly thermal linewidths , particularly those which appear to be starless ( using Spitzer data ) , indicating turbulent support on the small scales of molecular clouds is minimal .
For those N _ { 2 } H ^ { + } targets which have an associated SCUBA dense core , we find their internal motions are more than sufficient to provide support against the gravitational force on the cores .
Comparison of the N _ { 2 } H ^ { + } integrated intensity and SCUBA flux reveals fractional N _ { 2 } H ^ { + } abundances between 10 ^ { -10 } and 10 ^ { -9 } .
We demonstrate that the relative motion of the dense N _ { 2 } H ^ { + } gas and the surrounding C ^ { 18 } O gas is less than the sound speed in the vast majority of cases ( \sim 90 % ) .
The point-to-point motions we observe within larger extinction regions appear to be insufficient to provide support against gravity , although we sparsely sample these regions .