target.rates

target.rates#

This module provides utility functions for drawing and computing volumetric rates and redshift distributions.

skysurvey.target.rates.draw_redshift(size, rate, zmin=0.0, zmax=2.0, zstep=0.0001, cosmology=FlatLambdaCDM(name='Planck18', H0=<Quantity 67.66 km / (Mpc s)>, Om0=0.30966, Tcmb0=<Quantity 2.7255 K>, Neff=3.046, m_nu=<Quantity [0., 0., 0.06] eV>, Ob0=0.04897), rng=None, **kwargs)[source]#

Draw random redshift following the given rate.

Parameters:

  • size (int) – Number of target to draw.

  • rate (float or callable) – If a float is given, it is assumed to be the number of targets per Gpc3. If a callable is given, it is supposed to be a function of z that returns the volumetric rate as a function of redshift.

  • zmin (float, optional) – Minimum redshift. The default is 0.

  • zmax (float, optional) – Maximum redshift. The default is 2.

  • zstep (float, optional) – Sampling of the redshift. The default is 1e-5.

  • cosmology (astropy.Cosmology, optional) – Cosmology to use to compute volume, as the rate are “volumetric rates”.

  • rng (None, int, (Bit)Generator, optional) – seed for the random number generator. (doc adapted from numpy’s np.random.default_rng docstring. See that documentation for details.) If None, an unpredictable entropy will be pulled from the OS. If an int, (>0), it will set the initial BitGenerator state. If a (Bit)Generator, it will be returned as a Generator unaltered.

  • **kwargs – Goes to get_ntargets_per_shell() -> get_rate().

Returns:

A list of redshifts.

Return type:

list

skysurvey.target.rates.get_rate(z, rate, **kwargs)[source]#

Get the (volumetric) rate as a function of redshift.

Parameters:

  • z (array) – Array of redshifts.

  • rate (float or callable) – If a float is given, it is assumed to be the number of targets per Gpc3. If a callable is given, it is supposed to be a function of z that returns the volumetric rate as a function of redshift.

  • **kwargs – Rate options if rate is a function. ignored otherwise.

Returns:

the rate per Gpc, array (if func) or float

Return type:

rate

skysurvey.target.rates.get_ntargets_per_shell(zmax, rate, zmin=0, zstep=1e-05, cosmology=FlatLambdaCDM(name='Planck18', H0=<Quantity 67.66 km / (Mpc s)>, Om0=0.30966, Tcmb0=<Quantity 2.7255 K>, Neff=3.046, m_nu=<Quantity [0., 0., 0.06] eV>, Ob0=0.04897), astype='int', **kwargs)[source]#

Get the total number of target expected in the given volume.

Parameters:

  • zmax (float) – outter redshift of the volume.

  • rate (float, array or callable) – If a float is given, it is assumed to be the number of targets per Gpc3. If a callable is given, it is supposed to be a function of z that returns the volumetric rate as a function of redshift. If an array is given, if array broacasts with shell size, then it multiplies shell, if not than an axes is added and pdf is (rates.shape, nbins).

  • zmin (float) – inner redshift of the volume.

  • cosmology (astropy.Cosmology, optional) – Cosmology used to get the comoving_volume. The default is Planck18.

  • zstep (float) – binning of the redshift used for the computation.

  • astype (bool) – type of the returned number of target per shell.

  • **kwargs – goes to get_rate()

Returns:

  • zbins (array) – mid value of the redshift corresponding to the shell

  • pdf (nd-array) – 1d array if rate broadcast with shell, else nd-array with n the rate shape.

skysurvey.target.rates.get_ntargets(zmax, rate, zmin=0, cosmology=FlatLambdaCDM(name='Planck18', H0=<Quantity 67.66 km / (Mpc s)>, Om0=0.30966, Tcmb0=<Quantity 2.7255 K>, Neff=3.046, m_nu=<Quantity [0., 0., 0.06] eV>, Ob0=0.04897), zstep=1e-05, force_shell=False, astype='int', **kwargs)[source]#

Get the total number of target expected in the given volume.

Parameters:

  • zmax (float) – outter redshift of the volume.

  • rate (float or callable) – If a float is given, it is assumed to be the number of targets per Gpc3. If a callable is given, it is supposed to be a function of z that returns the volumetric rate as a function of redshift.

  • zmin (float) – inner redshift of the volume.

  • cosmology (astropy.Cosmology, optional) – Cosmology used to get the comoving_volume. The default is Planck18.

  • zstep (float) – binning of the redshift used for the computation.

  • force_shell (bool) – If the input rate is a constant, should this force the use of shell computation ?

  • astype (bool) – type of the returned value.

Returns:

ntargets – number(s) of target.

Return type:

float, array