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تسجيل مستخدم جديدRadio galaxies and their magnetic fields out to z <= 3
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We present polarisation properties at $1.4,$GHz of two separate extragalactic source populations: passive quiescent galaxies and luminous quasar-like galaxies. We use data from the {it 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, and $1.4,$GHz luminosity of $6times10^{21}<L_{rm 1.4}<7times10^{25},$W Hz$^{-1}$, while the quasar-like galaxies have smaller percentage polarisation, larger radio linear size at radio wavelengths, and a $1.4,$GHz luminosity of $9times10^{23}<L_{rm 1.4}<7times10^{28},$W Hz$^{-1}$, suggesting that the environment of the quasar-like galaxies is responsible for the lower percentage polarisation. Our results confirm previous studies that found an inverse correlation between percentage polarisation and total flux density at $1.4,$GHz. 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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