skypy.power_spectrum.growth_function

skypy.power_spectrum.growth_function(redshift, cosmology, gamma=0.5454545454545454, z_upper=1100)

Growth function.

Function used to calculate \(D(z)\), growth function at different redshifts, as described in [1] equation 16.

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, optional

Growth index providing an efficient parametrization of the matter perturbations. Default is the 6/11 LCDM value.

z_upperfloat, optional

Redshift for the early-time integral cutoff. Default is 1100.

Returns

growth_function(nz,) array_like

The redshift scaling of the growth function.

References

1

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

Examples

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

>>> import numpy as np
>>> from scipy import integrate
>>> from astropy.cosmology import FlatLambdaCDM
>>> cosmology = FlatLambdaCDM(H0=67.04, Om0=0.3183, Ob0=0.047745)
>>> growth_function(0, cosmology)
0.7909271056297236