EPoS Contribution
EPoS Contribution
Slow magnetic dissipation in quiescent dark cores revealed by the HINSA Zeeman observations

Tao-Chung Ching
NAOC, Beijing, CN
We present the first clear evidence of evolving magnetic field in the center of quiescent dark molecular clouds. The strength of the magnetic field was derived from the Zeeman signature of the HI narrow self-absorption (HINSA) feature. HINSA zeeman measurements have crucial advantages over the more common spectral tracers, such as OH that is predicted to disappear in dense gas due to chemical evolution and CN that tends to suffer depletion. The combined analysis of both OH and HINSA Zeeman measurements reveal an evolving magnetic field, losing strength from outside-in, consistent with the classical ambipolar diffusion mechanism, which has long been proposed, but rarely corroborated by observations. Our observation and analysis thus support a relatively long time scale for star formation, due to the requirement to dissipate magnetic support.
Caption: The HINSA Stokes I and V spectra in L1544 of the Five-Hundred-meter Aperture Spherical (FAST) Telescope
Collaborators:
D. Li, NAOC, CN
C. Heiels, UC Berkely, US
Suggested Session: Magnetic Fields