Abstract:
We investigate the dependence of residual rotation measure (RRM) on intervening absorption
systems at cosmic distances by using a large sample of 539 Sloan Digital Sky survey quasars
in conjunction with the available rotation measure catalogue at around 21 cm wavelength. We
found an excess extragalactic contribution in the standard deviation of an observed RRM (σᵣᵣm )
of about 8.11 ± 4.83 rad m⁻² in our sample with an intervening Mg II absorber as compared
to the sample without an Mg II absorber. Our results suggest that intervening absorbers could
contribute to the enhancement of RRM at around 21 cm wavelength, as was found earlier for
rotation measure measurements at around 6 cm wavelength.
