Local measurement of H₀

Synopsis

Prototype class for local Hubble parameter measurements

Author

Jesus Torrado, Pablo Lemos

This is a simple gaussian likelihood for the latest local \(H_0\) measurements using a combination of different data.

It defines the following likelihoods

• H0.riess2018a: A legacy local measurement of \(H_0\), used in the analysis of Planck data for the Planck 2018 release. (arXiv:1801.01120)

• H0.riess2018b: Updated local measurement of \(H_0\). (arXiv:1804.10655)

• H0.riess201903: Riess et al. 2019 constraint (arXiv:1903.07603)

• H0.riess2020: Riess et al. 2020 constraint (arXiv:2012.08534)

• H0.freedman2020: Freedman et al. 2020 constraint (arXiv:2002.01550)

The above are all based on simple Gaussian posteriors for the value of H0 today, which is not what is directly measured. It can be more accurate to put a constraint on the intrinsic magnitude, which can then be combined with Supernovae constraints to relate to the expansion. An example is provided in

• H0.riess2020Mb: Riess et al. 2020 constraint on M_b (arXiv:2012.08534)

which should be run in combination with sn.pantheon with use_abs_mag: True (contributed by Pablo Lemos).

Using a different measurement

If you would like to use different values for the \(H_0\) constraint, as a mean and a standard deviation, simply add the following likelihood, substituting mu_H0 and sigma_H0 for the respective values:

likelihood:
  my_H0:
    external: 'lambda _self: -0.5 * (_self.provider.get_param("H0") - mu_H0)**2 / (sigma_H0)**2'
    requires: ["H0"]