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 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 6 \times 10 ^ { 21 } < L _ { 1.4 } < 7 \times 10 ^ { 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 9 \times 10 ^ { 23 } < L _ { 1.4 } < 7 \times 10 ^ { 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 .