CN Zeeman measurements in star formation regions

¹ LERMA/LRA, CNRS UMR 8112, École Normale Supérieure and Observatoire de Paris, 24 rue Lhomond, 75231 Paris Cedex 05, France e-mail: edith@lra.ens.fr
² University of Kentucky, Department of Physics and Astronomy, Lexington, KY 40506, USA e-mail: troland@pa.uky.edu
³ University of Illinois, Department of Astronomy, Urbana, IL 61801, USA e-mail: crutcher@uiuc.edu
⁴ IRAM, 7 avenida Divina Pastora, Granada, Spain e-mail: paubert@iram.es

Received: 14 February 2008
Accepted: 17 May 2008

Abstract

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  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  mG while the average density of the medium sampled is 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 to 4 with respect to critical. Their turbulent and magnetic energies are in approximate equipartition.