ScaleFactor

class astropy.cosmology.traits.ScaleFactor

Bases: object

The trait for computing the cosmological scale factor.

The scale factor is defined as \(a = a_0 / (1 + z)\).

Attributes Summary

scale_factor0

Scale factor at redshift 0.

Methods Summary

scale_factor(z)

Compute the scale factor at redshift z.

Attributes Documentation

scale_factor0

Scale factor at redshift 0.

The scale factor is defined as \(a = a_0 / (1 + z)\). The common convention is to set \(a_0 = 1\). However, in some cases, like in some old CMB papers, \(a_0\) is used to normalize a to be a convenient number at the redshift of interest for that paper. Explicitly using \(a_0\) in both calculation and code avoids ambiguity.

Methods Documentation

scale_factor(z)

Compute the scale factor at redshift z.

The scale factor is defined as \(a = a_0 / (1 + z)\).

Parameters:

zQuantity-like [‘redshift’] | numpy:array_like

Input redshift.

Changed in version 7.0: Passing z as a keyword argument is deprecated.

Returns:

|Quantity|

Scale factor at each input redshift.