schechter_lf_redshift

skypy.galaxy.redshift.schechter_lf_redshift(redshift, M_star, phi_star, alpha, m_lim, fsky, cosmology, noise=True)

Sample redshifts from Schechter luminosity function.

Sample the redshifts of galaxies following a Schechter luminosity function with potentially redshift-dependent parameters, limited by an apparent magnitude m_lim, for a fraction fsky of the sky.

Parameters

redshiftarray_like

Input redshift grid on which the Schechter function parameters are evaluated. Galaxies are sampled over this redshift range.

M_stararray_like or function

Characteristic absolute magnitude of the Schechter function. Can be a single value, an array of values for each redshift, or a function of redshift.

phi_stararray_like or function

Normalisation of the Schechter function. Can be a single value, an array of values for each redshift, or a function of redshift.

alphaarray_like or function

Schechter function power law index. Can be a single value, an array of values for each redshift, or a function of redshift.

m_limfloat

Limiting apparent magnitude.

fskyarray_like

Sky fraction over which galaxies are sampled.

cosmologyCosmology, optional

Cosmology object to convert apparent to absolute magnitudes. If not given, the default cosmology is used.

noisebool, optional

Poisson-sample the number of galaxies. Default is True.

Returns

redshiftsarray_like

Redshifts of the galaxy sample described by the Schechter luminosity function.

Examples

Compute the number density of galaxies with redshifts between 0 and 5 for typical values of the “blue” galaxy luminosity function above an apparent magnitude cut of 22 for a survey of 1 square degree = 1/41253 of the sky.

>>> from skypy.galaxy.redshift import schechter_lf_redshift
>>> z = [0., 5.]
>>> M_star = -20.5
>>> phi_star = 3.5e-3
>>> alpha = -1.3
>>> z_gal = schechter_lf_redshift(z, M_star, phi_star, alpha, 22, 1/41253)