skypy.power_spectrum.growth_factor

skypy.power_spectrum.growth_factor(redshift, cosmology, gamma=0.5454545454545454)

Growth factor.

Function used to calculate \(f(z)\), parametrised growth factor as a function of redshift, as described in [1] equation 17.

Parameters

redshift(nz,) array_like

Array of redshifts at which to evaluate the growth function.

cosmologyastropy.cosmology.Cosmology

Cosmology object providing methods for the evolution history of omega_matter and omega_lambda with redshift.

gammafloat

Growth index providing an efficient parametrization of the matter perturbations.

Returns

growth_factor(nz,) array_like

The redshift scaling of the growth factor.

References

1

5. 22. Linder, Phys. Rev. D 72, 043529 (2005)

Examples

This example returns the growth factor for a given array of redshifts and for a given cosmology:

>>> import numpy as np
>>> from astropy.cosmology import FlatLambdaCDM
>>> cosmology = FlatLambdaCDM(H0=67.04, Om0=0.3183, Ob0=0.047745)
>>> growth_factor(0, cosmology)
0.5355746155304598