VLA HI Zeeman observations of Centaurus A

We present H I absorption observations toward the nucleus and neighboring radio features of Centaurus A, with the aim of studying the magnetic field using the Zeeman effect. The H I profiles toward the nucleus reveal for the first time a broad absorption component that extends up to 635 km s(-1) and is centered near 583 km s(-1). This broad component may be a blend of absorption in several clouds located in the similar to100 pc radius circumnuclear ring of Cen A. We set upper limits on the line-of-sight magnetic field (B-los) in Cen A in the regions traced by the H I absorption components. The best value (fit +/- 1 sigma error) for B-los in the dust lane is -3 +/- 7 muG. For the redshifted narrow line width components observed toward the nucleus, B-los is similar to10 +/- 20 muG. If we assume the spin temperature T-s less than or equal to 50 K in these redshifted clouds, our analysis shows that the magnetic fields will be energetically significant if B-los greater than or equal to 5 muG for cloud sizes around a few parsecs or larger.