sncosmo.zdist

sncosmo.zdist(zmin, zmax, time=365.25, area=1.0, ratefunc=<function <lambda>>, cosmo=FlatLambdaCDM(H0=70.0 km / (Mpc s), Om0=0.3, Tcmb0=0.0 K, Neff=3.04, m_nu=None, Ob0=None))

Generate a distribution of redshifts.

Generates the correct redshift distribution and number of SNe, given the input volumetric SN rate, the cosmology, and the observed area and time.

Parameters:

zmin, zmaxfloat

Minimum and maximum redshift.

timefloat, optional

Time in days (default is 1 year).

areafloat, optional

Area in square degrees (default is 1 square degree). time and area are only used to determine the total number of SNe to generate.

ratefunccallable

A callable that accepts a single float (redshift) and returns the comoving volumetric rate at each redshift in units of yr^-1 Mpc^-3. The default is a function that returns 1.e-4.

cosmoCosmology, optional

Cosmology used to determine volume. The default is a FlatLambdaCDM cosmology with Om0=0.3, H0=70.0.

Examples

Loop over the generator:

>>> for z in zdist(0.0, 0.25):
...     print(z)
...
0.151285827576
0.204078030595
0.201009196731
0.181635472172
0.17896188781
0.226561237264
0.192747368762

This tells us that in one observer-frame year, over 1 square degree, 7 SNe occured at redshifts below 0.35 (given the default volumetric SN rate of 10^-4 SNe yr^-1 Mpc^-3). The exact number is drawn from a Poisson distribution.

Generate the full list of redshifts immediately:

>>> zlist = list(zdist(0., 0.25))

Define a custom volumetric rate:

>>> def snrate(z):
...     return 0.5e-4 * (1. + z)
...
>>> zlist = list(zdist(0., 0.25, ratefunc=snrate))