Dynamics of Dense Cores in the Perseus Molecular Cloud

TL;DR

This study investigates the kinematics of dense cores in the Perseus molecular cloud, revealing minimal turbulence, sufficient internal support against gravity, and small relative motions between dense gas and surroundings, enhancing understanding of star formation processes.

Contribution

It provides detailed kinematic analysis of dense cores using N2H+ and C18O observations, highlighting the support mechanisms and motions relevant to star formation.

Findings

Dense N2H+ cores show nearly thermal linewidths.

Internal motions in cores can support against gravity.

Dense gas motions are generally subsonic relative to surroundings.

Abstract

We survey the kinematics of over one hundred and fifty candidate (and potentially star-forming) dense cores in the Perseus molecular cloud with pointed N2H+(1-0) and simultaneous C18O(2-1) observations. Our detection rate of N2H+ is 62%, rising to 84% for JCMT SCUBA-selected targets. In agreement with previous observations, we find that the dense N2H+ 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 N2H+ 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 N2H+ integrated intensity and SCUBA flux reveals fractional N2H+ abundances between 10^-10 and 10^-9. We demonstrate that the relative motion of the dense N2H+ gas and the surrounding C18O gas is less than the sound speed in the vast majority of cases (~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.