 Compilation of cz (radial velocity) measurements Search the compilation of cz measurements

The catalog (table a110 in the database) presents the compilation of redshift of galaxies, z,

z = (λ-λ0) / λ0 = (ν0-ν) / ν
where λ and λ0 refer the observed and emitted wavelength, ν and ν0 are the observed and emitted frequency. The data are stored in units of km/s as cz, where c is the speed of light (299792.458 km/s). The redshift should be reduced to heliocentric restframe, where the rotation of Earth and orbital motions have been removed from the measured velocity.
The observed shift in wavelength or frequency of light emitted by an object consists of relativistic Doppler effect, gravitational and cosmological redshifts. We can neglect the gravitational redshift in most of cases of extragalactic astronomy because the effect is very small. The cosmological redshift arises due to Hubble expansion of the Universe. The relativistic Doppler effect appears because of physical motion of the object and observer with respect to each other. See also the article on redshift from Wikipedia.

Statistics of the compilation of cz measurements

The ten main references for this compilation are:

The first ten sources of redshifts

The relativistic Doppler effect is appeared due to relative motion of the observer and the source. The redial velocity can be expressed from the observable shift in the frequency or in the wavelength as
V = c (ν022) / (ν022) = c (λ202) / (λ202) = c [(1+z)2-1] / [(1+z)2+1]
There are two frequently used approximations of this equation for small z, the "optical" and "radio" conventions.

So called "optical" convention is

Voptic = c (λ-λ0) / λ0 = cz
Thus, for small z, z << 1, the value, cz, can be treated as radial velocity of the object. Because of it, the therminology "radial velocity" is often used as synonym of the redshift, cz. Many catalogs, databases and surveys use the "radial velocity" to refer the redshift. Of course, this interpretation can not be applied to object on high z.