Problems with Pantheon+ and wCDM

[DinorahBarbosa]

Hi,

So, recently I've been trying to use Pantheon+ (as well as Pantheon+SH0ES) to constrain wCDM but weirdly enough, it seems to be incapable of imposing constrains on w0_fld. Below is my .param file as is

data.experiments=['Pantheon_Plus_SH0ES']

# Cosmological parameters list
# Priors from table 9 of arXiv: 2007.08991
data.parameters['Omega_m']    = [ 0.295,   0.1, 0.9,     0.02,    1, 'cosmo']
data.parameters['H0']      = [  70,   20, 100,      1, 1, 'cosmo']
data.parameters['w0_fld'] = [-1., -2., 0., 0.08, 1, 'cosmo']

# Nuisance parameters list
data.parameters['M']       = [-19.2, -30, -10, 0.5,  1, 'nuisance']

# Fixed cosmological parameters
data.cosmo_arguments['n_s'] = 0.96
data.cosmo_arguments['ln10^{10}A_s'] = 3.05
data.cosmo_arguments['tau_reio'] = 0.06
data.cosmo_arguments['Omega_Lambda'] = 0.
data.cosmo_arguments['Omega_b'] = 0.0468
# Three massive neutrinos with sum(mnu)=0.06eV and Neff = 3.044
data.cosmo_arguments['N_ur'] = 0.00441
data.cosmo_arguments['N_ncdm'] = 1
data.cosmo_arguments['deg_ncdm'] = 3
data.cosmo_arguments['m_ncdm'] = 0.02
data.cosmo_arguments['T_ncdm'] = 0.71611

#------ Mcmc parameters ----

data.N=100000
data.write_step=5

I also did a run with LCDM and it went perfectly fine constraining Omega_Lambda. I ran the above script with 400k points, the contours for the other parameters are ok.

Thanks in advance!

Dinorah

[brinckmann]

Hi Dinorah,

Looking at https://arxiv.org/abs/2202.04077 figure 9 and table 3 I would indeed expect a weak constraint around w0 = −0.90 ± 0.14 when using just the Pantheon+SH0ES likelihood. Did your LCDM constraints match the article? Omega_M = 0.334 ± 0.018, Omega_Lambda = 0.666 ± 0.018, H0 = 73.6 ± 1.1

@PoulinV are you aware of any issues in the public MontePython version of this likelihood (or have any ideas about what went wrong here)? If you have your own version, could you do a diff to see if there are differences (or send me a copy and I'll check them out)? Thanks!

Best, Thejs