The radial distance must be supplied using the r_parsec
parameter. A naive estimate from quantities in the Gaia
source catalogue may be made with the expression
1000./parallax
,
though note that this simple inversion of parallax
is not in general reliable for parallaxes with non-negligable errors.
The calculations are fairly straightforward,
following Eq. 1.5.74 from the Hipparcos catalogue.
A (usually small) Doppler factor accounting for light-time effects
can also optionally be applied. The effect of this is to multiply
the returned vector by a factor of 1/(1-radial_velocity/c)
,
as discussed in Eq. 1.2.21 of the Hipparcos catalogue.
Note that no attempt is made to adjust for solar motion.
astromUVW(ra, dec, pmra, pmdec,
radial_velocity, dist, true)
icrsToGal(astromUVW(ra, dec, pmra, pmdec,
radial_velocity, 1000./parallax, false))