Joachimi_Bridle_alpha

Calculate the gradient of the galaxy luminosity function at the limiting magnitude of the survey.

File	luminosity_function/Joachimi_Bridle_alpha/interface.py
Attribution	CosmoSIS team
	Simon Samuroff
URL

The gradient of the cumulative galaxy luminosity function alpha is sensitive to both redshift and magnitude limit of the survey considered. Joachimi & Bridle (2010) extend the fitting function of Blake & Bridle (2005) to obtain a polynomial alpha(z, r_lim) at a range of redshifts, where z_i is the median in redshift bin i and r_lim is the r-band magnitude limit. Note that the fitting is based on ground-based data from the COMBO-17 survey. See Joachimi & Bridle (2010) for discussion of its applicability.

Assumptions

• The galaxy luminosity function is well approximated by the fitting function of Blake & Bridle (2005).

• The limiting r-band magnitude r_lim>16.9

Setup Parameters

Name	Type	Default	Description
magnitude_limit	real	24.0	Limiting r-band magnitude of the survey considered.
binned_alpha	bool	True	Compute alpha in the survey redshift bins, rather than as a continuous funtion of redshift.

Input values

Section	Name	Type	Default	Description
wl_num_density	Nz	int		Number of points used to evaluate the distribution in each redshift bin.
	nzbin	int		Number of survey redshift bins.
	zmax	real		Maximum redshift of the redshift distributions.
	bin_{i}	real 1d		An array of Nz points evenly sampled from the galaxy redshift distribution in bin i in the range z={0…zmax}. The index ranges i={0, 1, …, nzbin}.

Output values

Output values

Section	Name	Type	Description
galaxy_luminosity_function	z	real 1d	Redshift values of alpha(z) samples
	alpha	real 1d	Gradient of the logarithmic cumulative galaxy luminosity function at the limiting magnitude.
	z_binned	real 1d	Median values of the n(z) in the survey redshift bins.
	alpha_binned	real 1d	Gradient of the logarithmic cumulative galaxy luminosity function at the limiting magnitude, evaluated at the median redshift of each bin.