clerkin

Compute galaxy bias as function of k, z for 3-parameter Clerkin et al 2014 model

File	bias/clerkin/clerkin_interface.py
Attribution	Clerkin
URL
Citations	arXiv:1405.5521
	Cole et al, MNRAS, 362, 2, 505–534

The GTD bias model provides a benchmark expression for the redshift evolution of galaxy bias on large scales. This is crucial for rigorous comparison or combination of results. Choice of biasing model has a significant impact on cosmological parameter constraints, and an incorrect bias model will cause a shift in measured values of cosmological parameters. The three parameter GTD model, which encompasses several common bias models, has been shown to outperform the popular approach of a binned constant bias in obtaining unbiased estimates of cosmological parameters.

The GTD model is:

\(b(z) = c + (b_0 - c) / D(z)^\alpha\)

where D(z) is the growth factor.

The Q model is:

\(b(k) = (1+Q k^2) / (a+A k)\)

This module creates bias fields and/or scales power spectra, depending on the chosen options

The version of this model without redshift dependence is from Cole et al.

Assumptions

• 3-parameter bias model from Clerkin et al l 2014

Setup Parameters

Name	Type	Default	Description
bias_only	bool	False	) If set, do not use the matter power spectrum, just save the bias field
model	str	gtd	Model choice. gtd, q, or q-gtd to use the GTD three-parameter model (z evolution only), the 2-parameter Q model (k scale only), or both
suffix	str	‘’	A suffix to append to the output section names below

Input values

Section	Name	Type	Default	Description
galaxy_bias	b0	real		Bias at z=0 if GTD model used
	c	real		Bias parameter for GTD model
	alpha	real		Power law index for growth in GTD model
	Q	real		Numerator parameter in Q model
	A	real		Denominator parameter in Q model
matter_power_nl	k_h	real 1d		Wavenumber in h/Mpc only if mode=power or both
	z	real 1d		Redshift only if mode=power or both
	P_k	real 2d		Nonlinear matter power only if mode=power or both

Output values

Output values

Section	Name	Type	Description
galaxy_power	k_h	real 1d	Wavenumber in h/Mpc, only if bias_only=F
	z	real 1d	Redshift, only if bias_only=F
	P_k	real 2d	Galaxy power, only if bias_only=F
matter_galaxy_power	k_h	real 1d	Wavenumber in h/Mpc, only if bias_only=F
	z	real 1d	Redshift, only if bias_only=F
	P_k	real 2d	Matter-galaxy cross power, only if bias_only=F
bias_field	k_h	real 1d	Wavenumber samples in h/Mpc of bias b(k, z)
	z	real 1d	Redshift samples
	b	real 2d	Galaxy bias b(k, z)
	r	real 2d	Stochastic bias r(k, z); identically 1 for these models.