gphist.distance module

Cosmological distance model.

class gphist.distance.HubbleDistanceModel(evol)

Bases: object

Models expansion history as multiplicative correction to the fiducial DH(z).

Parameters:evol – evolution parameter to use, which must have a zvalues attribute and implement a get_DC method.
get_DH(samples)

Build expansion histories from Gaussian process samples.

Each sample gamma(z) generates a Hubble distance function DH(z) = DH0(z)*exp(gamma(z)).

Parameters:samples (ndarray) – 2D array with shape (num_samples,num_steps) of num_samples samples gamma(z) tabulated at the num_steps redshifts z given in zvalues.
Returns:1D array with shape (num_steps,) of tabulated DH(z) values.
Return type:ndarray
gphist.distance.convert_DC_to_DA(DH, DC, omega_k)

Applies curvature to convert DC(z) into DA(z).

Parameters:
  • DH (ndarray) – input array with shape (nh,nz) of nh comoving distance functions DC(z) each tabulated at nz redshifts. Only the slice DH[:,0] corresponding to z=0 is actually used.
  • DC (ndarray) – input array with shape (nh,nz) of nh comoving distance functions DC(z) each tabulated at nz redshifts starting with z=0. The input values are overwritten with DA values.
  • omega_k (float) – curvature parameter Omega_k.
Returns:

a reference to the input array DC which now contains

values of DA.

Return type:

ndarray