Background geometry (geometry)

Compute geometrical quantities in a cosmological background.

redshift_from_distance(cosmo[, lg_num_sample])

Invert redshift-to-distance relationship of a cosmological model to redshift-from-distance.

differential_AP_distortion(fiducial_z_to_r, ...)

Compute the differential Alcock--Paczynski distortion between a fiducial and a cosmological redshift-to-distance conversion as a fuction of redshift.

harmonia.cosmology.geometry.redshift_from_distance(cosmo, lg_num_sample=5)[source]

Invert redshift-to-distance relationship of a cosmological model to redshift-from-distance.

Notes

This is useful when the Alcock–Paczynski effect needs to be included in modelling. Only valid for redshift between 1.e-3 and 100.

Parameters:

  • cosmo (nbodykit.cosmology.cosmology.Cosmology) – Cosmological model.

  • lg_num_sample (float, optional) – Base-10 logarithm of the number of redshift points to sample the comoving distance as a function of redshift (default is 5, i.e. 100000 samle points).

Returns:

Redshift-from-distance function.

Return type:

callable

harmonia.cosmology.geometry.differential_AP_distortion(fiducial_z_to_r, variable_z_to_r, max_redshift=10.0, lg_num_sample=5)[source]

Compute the differential Alcock–Paczynski distortion between a fiducial and a cosmological redshift-to-distance conversion as a fuction of redshift.

Parameters:

  • fiducial_z_to_r (callable) – Fiducial redshift-to-distance conversion.

  • variable_z_to_r (callable) – Variable redshift-to-distance conversion.

  • max_redshift (float, optional) – Maximum redshift to sample for interpolation (default is 10).

  • lg_num_sample (float, optional) – Base-10 logarithm of the number of redshift points to sample the differential distortion as a function of redshift (default is 5, i.e. 100000 samle points).

Returns:

Differential distortion as a fuction of redshift.

Return type:

callable