Fanaroff-Riley dichotomy of radio galaxies and the Malmquist bias
  We examine the possibility that a claimed dependence of the FR 1/2 break
value in radio luminosity on the absolute magnitude of the optical host galaxy
could be due to the Malmquist bias, where a redshift-luminosity correlation
appears in a flux-limited sample because of an observational selection effect.
In such a sample, the redshift dependence of a phenomenon could appear as a
luminosity-dependent effect and may not be really representing an intrinsic
property of the radio sample. We test this on the radio complete MRC (Molonglo
Reference Catalog) sample, where Spearman rank correlation and Kendall rank
correlation tests show that the correlations are indeed stronger between the
redshift and the optical luminosity than that between the radio luminosity and
the optical luminosity, suggesting that the latter correlation perhaps arises
because of the Malmquist Bias. We further show that similar effects of the
Malmquist bias could also be present elsewhere in other correlations claimed in
the literature between the radio luminosity and other observed properties of
FR1 and FR2 sources.
