Alma Mater Studiorum Universit`a degli Studi di Bologna ... - Inaf

Chapter 6
Faraday rotation in two extreme
environments ‡
In this Chapter I will present polarization analyses of two radio galaxies embedded in very
different environments. The sources are: B2 0755+37, located in a very sparse group, and
M 87, located at the centre of the cool core Virgo cluster. I will described the results of twodimensional
analyses of the RM and depolarization distributions. In both sources, the geometry
of the surrounding X-ray emitting gas appears to be complex than for the sources studied in
Chapters 4 and 5, so a three-dimensional analysis will be deferred to a later study.
6.1 The sources
The general parameters of the sources are listed in Table 6.1, while Table 6.2 shows the X-ray
parameters taken from the literature and the equipartition parameters derived from radio data in
this work. I refer to parts of the sources by the abbreviations N, S, E, W (for North, South, East,
West).
6.1.1 B2 0755+37
B2 0755+37 (hereafter 0755+37) is an extended FR I radio source whose optical counterpart,
NGC 2484, is a D-galaxy, classified as central member of a nearby and very poor group of galaxies
(Mulchaey et al. 2003). The source is one of the most isolated radio galaxies in the B2 catalogue.
Here I briefly summarize the radio properties of 0755+37, which are described in detail in the
Appendix of this thesis along with a description of the VLA observations. At a resolution of
‡ Guidetti et al. in prep
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