Cosmology (ligo.skymap.postprocess.cosmology)

Cosmology-related utilities.

All functions in this module use the Planck15 cosmological parameters.

ligo.skymap.postprocess.cosmology.dDL_dz_for_z(z)

Derivative of luminosity distance with respect to redshift.

ligo.skymap.postprocess.cosmology.dVC_dVL_for_DL(DL)

Same as dVC_dVL_for_z(), but as a function of luminosity distance.

ligo.skymap.postprocess.cosmology.dVC_dVL_for_z(z)

Ratio, $\mathrm{d}{V}_C/\mathrm{d}{V}_L$, between the comoving volume element and a naively Euclidean volume element in luminosity distance space; given as a function of redshift.

Given the differential comoving volume per unit redshift, $\mathrm{d}{V}_C/\mathrm{d}z$, and the derivative of luminosity distance in terms of redshift, $\mathrm{d}{D}_L/\mathrm{d}z$, this is expressed as:

$$\frac{\mathrm{d}{V}_C}{\mathrm{d}{V}_L}=\frac{\mathrm{d}{V}_C}{\mathrm{d}z}{\left({D_L}^2\frac{\mathrm{d}{D}_L}{\mathrm{d}z}\right)}^{-1}.$$