no_bias

Generate galaxy power P(k) as though galaxies were unbiased DM tracers

File	bias/no_bias/no_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(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=1. It generates the galaxy power and matter-galaxy cross-power from the non-linear power spectrum, just by copying them.

This can be useful if you plan to apply a more complicated bias model to calculated observables later, for example.

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

Assumptions

• Unit galaxy bias; at all scales and redshifts galaxies perfectly trace dark matter

Setup Parameters

None

Input values

Section	Name	Type	Default	Description
matter_power_nl	k_h	real 1d		Wavenumber in h/Mpc of NL matter power
	z	real 1d		Redshift of NL matter power
	P_k	real 2d		Nonlinear matter power
matter_intrinsic_power	k_h	real 1d		Wavenumber in h/Mpc of matter-intrinsic power (optional)
	z	real 1d		Optional, redshift
	P_k	real 2d		Optional, nonlinear matter power

Output values

Output values

Section	Name	Type	Description
galaxy_power	k_h	real 1d	Wavenumber in h/Mpc
	z	real 1d	Redshift
	P_k	real 2d	Galaxy power
matter_galaxy_power	k_h	real 1d	Wavenumber in h/Mpc
	z	real 1d	Redshift
	P_k	real 2d	Matter-galaxy cross power
galaxy_intrinsic_power	k_h	real 1d	Only if matter_intrinsic_power found, wavenumber in h/Mpc
	z	real 1d	Only if matter_intrinsic_power found, optional, redshift
	P_k	real 2d	Only if matter_intrinsic_power found, optional, nonlinear matter power