CN Zeeman measurements in star formation regions

Aims. Magnetic fields play a primordial role in the star formation process. The Zeeman effect on the CN radical lines is one of the few methods of measuring magnetic fields in the dense gas of star formation regions. Methods. We report new observations of the Zeeman effect on seven hyperfine CN N = 1-0 lines in the direction of 14 regions of star formation. Results. We have improved the sensitivity of previous detections, and obtained five new detections. Good upper limits are also achieved. The probability distribution of the line-of-sight field intensity, including non-detections, provides a median value of the total field B-tot = 0.56 mG while the average density of the medium sampled is n(H-2) = 4.5 x 10(5)cm(-3). We show that the CN line probably samples regions similar to those traced by CS and that the magnetic field observed mostly pervades the dense cores. The dense cores are found to be critical to slightly supercritical with a mean mass-to-flux ratio M/Phi similar to 1 to 4 with respect to critical. Their turbulent and magnetic energies are in approximate equipartition.