## The role of bbn_consistency flag in CosmoMC

Use of Healpix, camb, CLASS, cosmomc, compilers, etc.
Erick Almaraz
Posts: 25
Joined: June 10 2012
Affiliation: University of Mexico

### The role of bbn_consistency flag in CosmoMC

Hello everybody.

I have some doubts on the role of the bbn_consistency flag in CosmoMC. First of all, by default this flag is set to T in batch2/params_CMB_defaults.ini:

Code: Select all

bbn_consistency = T
As far as I see, this means that we use the Parthenelope fitting table (at $COSMOMC/data) just to calculate the primordial abundances of helium and deuterium as a function of omegabh2 and the extra relativistic number of species (see source/CosmologyParametrizations). These calculations are just theoretical predictions, since the program does not handle observational data on that subject against which these predictions can be compared. Am I right? Regards Antony Lewis Posts: 1352 Joined: September 23 2004 Affiliation: University of Sussex Contact: ### Re: The role of bbn_consistency flag in CosmoMC That's right. (there is a dataset format for element abundance data as well) Erick Almaraz Posts: 25 Joined: June 10 2012 Affiliation: University of Mexico ### The role of bbn_consistency flag in CosmoMC Dear Antony. Thanks for the quick reply. I suppose that the abundance data you mention is the Cooke's and Izotov's measurements of primordial deuterium and helium, respectively (these data can be found at$COSMOMC/data/D_Cooke2013.dataset & Yp_Izotov2014.dataset). If I'd like to take into account this information in my analysis, I guess that I would have to include batch2/abundances.ini in my ini file. Am I right?

Regards

Antony Lewis
Posts: 1352
Joined: September 23 2004
Affiliation: University of Sussex
Contact:

### Re: The role of bbn_consistency flag in CosmoMC

Yes, just include/edit batch2/abundances.ini as required.