Session 53 -- Cluster Cooling Flows and Abundances
Display presentation, Thursday, January 13, 9:30-6:45, Salons I/II Room (Crystal Gateway)

## [53.10] Radio Polarimetry of 3C\,84 (NGC~1275)

Jingping Ge and David H. Roberts (Brandeis University)

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The bright radio source 3C\,84 is associated with the giant elliptical NGC~1275. An extensive X-ray halo surrounds NGC~1275, and the morphology indicates that the gas in the cluster core is cooling and accreting onto NGC~1275 (Fabian \etal\ 1981). NGC~1275 is surrounded by a unique system of H$\alpha$ filaments. The central regions of NGC~1275 have broad emission lines and a compact optical continuum source.

3C\,84 is an example of a core dominated radio source. Most sources of this type are associated with quasars at high redshift. The optical and radio properties of 3C\,84 are more closely related to those of BL~Lacertae objects. The relative proximity of 3C\,84 allows a detailed study of polarization to explore the magnetic field structure, thermal environment, and kinematics of this compact radio source. 3C\,84 has very low integrated polarization compared to most core-dominated sources, which typically show significant polarization on both arcsecond and milliarcsecond scales. This could be due to depolarization from a huge Faraday rotation in the hot cluster medium or the cold line emitting medium.

We present recent VLA and VLBI observations of 3C\,84. The high dynamic range (200,000:1) VLA image of 3C\,84 was made at 3.6~cm in the spectral-line mode. Special calibration techniques were used to correct for the time variation of the VLA polarization response. These observations show that compact core is not polarized (less than 0.05\%). 3C\,84 has been used as a VLBI polarization calibrator because of its low integrated polarization (Roberts, Wardle, \& Brown 1994). We have reanalyzed our Mk~III VLBI data using AIPS to search for very weak polarization on parsec scales. We found no polarization from any component (polarized flux less than 10~mJy).

This work was supported by grants from the National Science Foundation to DHR.