Heliocentric cz

The heliocentric cz, v is the error-weighted average of vopt and vrad which are both derived from the compilation of redshifts.

v is used to compute the redshift in other reference frames: Namely in the Local Group referential, vlg, the Galactic referential, vgsr, the Virgo cluster referential, vvir, and the CMB referential, v3k.