Astronomy and Astrophysics – Astronomy
Scientific paper
Dec 2006
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2006aas...209.0804h&link_type=abstract
2007 AAS/AAPT Joint Meeting, American Astronomical Society Meeting 209, #08.04; Bulletin of the American Astronomical Society, V
Astronomy and Astrophysics
Astronomy
2
Scientific paper
Circular polarization represents a tiny fraction of the synchrotron emission from extra-galactic radio jets; however, it has the potential to reveal important clues about their three-dimensional magnetic field structure and low energy particle population. We are currently obtaining multi-epoch circular polarization images of a large sample of active galactic jets with the MOJAVE VLBA program, and have started a follow-up program to obtain deep multi-frequency VLBA observations of the strongest detections. With this new program we are obtaining the first ever parsec-scale spectra of circular polarization at more than two frequencies. We present first results from recent six-frequency VLBA observations (from 8.0 to 24 GHz) of 18 Extra-galactic radio jets. Three well known radio jets: 3C84, 3C279, and 3C380 show different, interesting frequency dependent trends. 3C84 displays a clear change in sign of the circular polarization with frequency with a peak in the circular polarization at 15 GHz; however, 3C279 has a consistent sign for its circular polarization with a fractional level that appears to hold steady or perhaps increase with frequency. Finally, 3C380 displays an intriquing trend with strong negative circular polarization at low frequency (8-9 GHz), decreasing in strength at the intermediate frequencies (12-15 GHz), and potentially switching to positive circular polarization at high frequency (22 24 GHz). These changes in 3C380 are accompanied by a strong increase in core flux and linear polarization with frequency.
This work has been supported by an award from Research Corporation. The VLBA is operated by the National Radio Astronomy Observatory, a facility of the National Science Foundation operated under cooperative agreement by Associated Universities, Inc.
Aller Hugh D.
Aller Margo F.
Homan Daniel C.
Lister Matthew L.
Wardle J. F.
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