constant_bias

Apply a galaxy bias constant with k and z.

File	bias/constant_bias/constant_bias.py
Attribution	CosmoSIS Team
URL

Galaxy bias relates the distribution of galaxies to the underlying (dark) matter field whose skeleton they trace.

The matter power spectrum of galaxies is related to that of matter by a bias:

P_gal(k,z) = b^2(k,z,…) P_m(k,z)

where the most general bias is a function of wavenumber k, redshift z, galaxy type, and a whole host of other values. Realistic bias models can be complicated; the purpose of this module is to act as a placeholder, usually when testing pipelines or forecasting.

In this module, b is just a single constant number. It generates the galaxy power and matter-galaxy cross-power from the non-linear power spectrum.

Optionally, if it finds you have generated the matter-intrinsic alignment cross-power, it will calculate and save the galaxy-intrinsic cross power from it.

Assumptions

• Galaxy bias constant with k and z

Setup Parameters

None

Input values

Section	Name	Type	Default	Description
galaxy_bias	b	real		Constant galaxy bias value.
matter_power_nl	k_h	real 1d		Wavenumber samples in h/Mpc for NL power
	z	real 1d		Redshift samples for NL power
	P_k	real 2d		Nonlinear matter power grid
matter_intrinsic_power	k_h	real 1d		Optional wavenumber in h/Mpc for matter-intrinsic cross-power
	z	real 1d		Optional redshift for matter-intrinsic cross-power
	P_k	real 2d		Optional nonlinear matter-intrinsic cross-power

Output values

Output values

Section	Name	Type	Description
galaxy_power	k_h	real 1d	Wavenumber in h/Mpc of galaxy density power
	z	real 1d	Redshift of galaxy density power
	P_k	real 2d	Galaxy density power spectrum
matter_galaxy_power	k_h	real 1d	Wavenumber in h/Mpc of matter-galaxy cross-power
	z	real 1d	Redshift of matter-galaxy cross-power
	P_k	real 2d	Matter-galaxy cross power
galaxy_intrinsic_power	k_h	real 1d	Wavenumber in h/Mpc of matter-intrinsic power (if computed)
	z	real 1d	Redshift of matter-intrinsic power (if computed)
	P_k	real 2d	Non-linear cross galaxy-intrinsic power spectrum (if computed)