Heliocentric radial velocity (cz) from radio measurements

vrad is computed from the radio (mostly HI) measurements in the compilation of redshifts by rejecting outliers and measurements marked for their bad quality and computing a weighted average of the remaining measurements. The "optical" measurements are homogenized and combined separately to produce another parameter, vopt, and both vopt and vrad are combined to produce v.

Details of the computation

The radio measurements are selected and weight-averaged. The weights are the inverse of the square of the errors. When the precision is not given it is assumed to be 0.3*resc+5.5, and if the resolution (resc) is not known, the precision is taken as 10 km/s.
HyperLeda Questions: prugniel@obs.univ-lyon1.fr