pantheon module

Likelihood of the Pantheon supernova analysis

Name: pantheon

File: cosmosis-standard-library/likelihood/pantheon/pantheon.py

Version: 2018

Author(s):

Scolnic et al (measurement)
CosmoSIS team (code)

URL: http://dx.doi.org/10.17909/T95Q4X

Cite:

Scolnic et al, ApJ, 859, 28

Rules:

None.

Assumptions:

Pantheon statistical and systematic analysis

Explanation

Supernova IA can be used as standardisable candles,
letting us estimate a redshift-distance relation.

The Pantheon sample collected together a combined SN IA
sample from the Pan-Starrs1, Medium Deep Survey, SDSS,
SNLS, and various HST data sets into a joint analysis.

This module uses that data set to constrain the distance modulus
vs redshift relation.

There are two Pantheon data variants - this version uses the
compressed (binned) version since it is much smaller and faster
to use and produces nearly identical results to the full version.
You can separately download and use the full version files if you
wish.

The Pantheon data release was analyzed with a much more complex code
in CosmoMC, but almost all of the machinery in that code was unusued,
because the various systematic effects that it implements were subsumed
into a single systematic covariance matrix. This code therefore omits
that machinery for simlicitiy.

##Parameters

These parameters can be set in the module's section in the ini parameter file.
If no default is specified then the parameter is required.

Parameter	Description
data_file	string, optional. File containing supernova measurements (default=module dir + /lcparam_DS17f.txt)
covmat_file	string, optional. File containing supernova measurements (default=module dir + /lcparam_DS17f.txt)
x_section	string, optional. Use to override the default datablock section for input theory redshift
x_name	string, optional. Use to override the default datablock name for input theory redshift
y_section	string, optional. Use to override the default datablock section for input theory distance modulus
y_name	string, optional. Use to override the default datablock name for input theory distance modulus
like_name	string, optional. Use to override the default named for the saved output likelihood
likelihood_only	bool, optional. Skip saving everything except the likelihood. This prevents you from using e.g. the Fisher matrix sampler but can be faster for quick likelihoods
include_norm	bool, default=F. Include the normalizing constant at the start of the likelihood. May be needed when comparing models.

##Inputs

These parameters and data are inputs to the module, either supplied as parameters by the sampler or computed by some previous module. They are loaded from the data block.

Section	Parameter	Description
distances	z	double 1D array, redshifts of calculated theory mu(z)
	mu	double 1D array, distance modulus mu(z) at given redshifts
supernova_params	M	double, SN IA absolute magnitude

##Outputs

These parameters and data are computed as outputs from the module

Section	Parameter	Description
likelihoods	pantheon_like	double. Gaussian likelihood value of supplied theory mu(z) and M
data_vector	pantheon_covariance	double. Fixed covariance matrix, only if likelihood_only=F
	pantheon_data	double 1D array. Fixed data vector mu_obs, only if likelihood_only=F
	pantheon_simulation	double 1D array. Simulated data vector including simulated noise for e.g. ABC, only if likelihood_only=F
	pantheon_theory	double 1D array. Predicted theory values mu_theory(z_obs) only if likelihood_only=F
	pantheon_chi2	double. chi^2 value, only if likelihood_only=F

Wiki

cosmosis / default_modules / pantheon_2018

pantheon module

Likelihood of the Pantheon supernova analysis