4.8. Volume Prior

The volume prior takes into account the fact that the volume sampled by a survey increases with redshfit. It increases therefore the likelihood of sources being at higher redshifts and disfavours low-redshift solutions where the volume sampled is very small. Phosphoros assumes a volume prior proportional to the redshift-dependent differential comoving volume, i.e. \(p(z)\propto dV_C(z)/dz\) (see Methodology: Priors, or the Phosphoros paper for more details).

In the GUI mode

Volume prior is simply included in the redshifts computation by selecting Volume Prior in the Compute Redshifts --> 3. Prior sub-panel.

In the CLI mode

Volume prior is enabled by setting --volume-prior=YES in the compute redshifts executable (by default it is NO). An effectiveness value different from 1 can be set with the command option --volume-prior-effectiveness (see Prior effectiveness).