Redshift effect on the timescale of quasar radio variability

Abstract

IT has been suggested (ref. 1 and McCrea (I.A.U. Symposium No. 63, 1972)) that the radio or optical variability of quasars should be related to their redshifts. If the latter originate from the Doppler effect, or are gravitational, the observed fluctuation rate of the radio or optical emission should also be redshifted, that is, slowed down, in proportion to 1 + z, where z is the usual redshift factor. Medd et al., measuring quasar flux densities with the Algonquin telescope, attempted to detect this effect by plotting the frequency of maxima occurrence in the flux-density curves against z but obtained an inconclusive result. Scargle2 also analysed the Algonquin observations, using the half-width of the autocorrelation function of the flux-density curve as a measure of fluctuation rate. Again, the results show considerable dispersion, but Scargle argues that regression analysis supports the expected relationship. We present here a preliminary version of an analysis based on the power spectrum of the flux-density curves, which establishes the expected result.