Licia Verde
Hands on cosmology
What do we know today
MCMC
Sample the posterior distribu8on (Bayesian)
GOAL:
Use MCMC outputs used to do a cosmological analysis of the most recent data
Find out what we know, or rather, what are the constraints on selected cosmological parameters, within selected models
Here they are: • Planck Legacy archive (balance between robustness and small errors)
Decide what you are interested in: LCDM model or simple extensions: curvature, neutrino families, neutrino masses, dark energy proper8es Decide which data set combina8on among those available (I would encourage you to cover all possible combina8on of data set/ neutrino proper8es so they you can compare findings)
Get the posterior constraints! And discuss.
hQp://pla.esac.esa.int/pla/aio/planckResults.jsp?
Get this
Here they are:
• Planck Legacy archive (balance between robustness and small errors)
Decide what you are interested in: LCDM model or simple extensions: curvature, neutrino families, neutrino masses, dark energy proper8es Decide which data set combina8on among those available (I would encourage you to cover all possible combina8on of data set/ neutrino proper8es so they you can compare findings)
Get the posterior constraints! And discuss.
hQp://pla.esac.esa.int/pla/aio/planckResults.jsp?
Anatomy of a chain output Weight, likelihood, parameter1, parameter2, ……….
To know the order of the parameters look at file with extension “paramnames”
There are 8 of these , just merge them, let’s call this a “chain”
By virtue of being an MCMC a weighted histogram for parameter x gives you the marginalized posterior for that parameter
For neutrino proper8es
• base_nnu: LCDM+neutrino mass • base_nnu: LCDM+Neff as parameter • base_nnu_mnu: LCDM+Neff+nu mass • base_nnu_yhe: LCDM+Neff+primordial Helium (in helium not fixed by BBN) • base_mnu_omegak LCDM+mass nu+ curvature
For data combo: • Planck_lowl (Planck only) • Planck_lowl_lowlike (Planck +WMAP polariza8on) use this one rather than the above
• +highL (includes ACT and SPT ground based data at high l, useful for beQer foreground control)
• +Lensing: inlcudes the CMB lensing signal from Planck • +BAO includes BAO • +SNLS or Union: supernovae data • +HST includes local Hubble constant measure • Post: the data set has been added via importance sampling
And the result is….
Parameter constraints: Neutrino mass Planck collabora8on, 2013, paper XVI
Parameter constraints: Neutrino species Planck collabora8on, 2013, paper XVI
Parameter constraints:
Neutrino species and total mass
With galaxy surveys
@ 95%CL
SDSS BOSS DR9 Wigglez
Riemer-Sørensen et al. 2013 Archidiacono et al 2013
Neutrino species and total mass
Advanced!
Archidiacono et al 2013 arxiv:1307.0637