Radio galaxies and their magnetic fields out to z <= 3

We recently had a paper ” Radio galaxies and their magnetic fields out to z <= 3″ published. This is the result of a discussion from 2010 and has resulted in another probe of the excellent NVSS. You can read the paper on arxiv.

In the paper we present polarisation properties for two separate extragalactic source populations: passive quiescent galaxies and luminous quasar-like galaxies. We use data from the Wide-Field Infrared Survey Explorer data to determine the host galaxy population of the polarised extragalactic radio sources. The quiescent galaxies have higher percentage polarisation, smaller radio linear size, while the quasar-like galaxies have smaller percentage polarisation, larger radio linear size at radio wavelengths. Our results confirm previous studies that found an inverse correlation between percentage polarisation and total flux density at 1.4GHz. We suggest that the population change between the polarised extragalactic radio sources is the origin of this inverse correlation and suggest a cosmic evolution of the space density of quiescent galaxies. Finally, we find that the extragalactic contributions to the rotation measures (RMs) of the nearby passive galaxies and the distant quasar-like galaxies are different. After accounting for the RM contributions by cosmological large-scale structure and intervening Mg\,{II} absorbers we show that the distribution of intrinsic RMs of the distant quasar-like sources is at most four times as wide as the RM distribution of the nearby quiescent galaxies, if the distribution of intrinsic RMs of the WISE-Star sources itself is at least several rad m−2 wide.

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