Spurious points in WMAP3 likelihood code

Use of Healpix, camb, CLASS, cosmomc, compilers, etc.
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Michael Bridges
Posts: 2
Joined: August 02 2006
Affiliation: Cavendish Astrophysics, Cambridge

Spurious points in WMAP3 likelihood code

Post by Michael Bridges » August 02 2006

Apologies if this has already been discussed -but I've seen some spurious model likelihoods from the WMAP code, specifically beyond about 2sigma there are some parameter combinations that give a likelihood in excess of 200 ln units better than the maximum?

e.g. WMAP3 (TT,TE,EE) data only:

lhood \Omega_b h^2 \Omega_c h^2 \theta \tau n_s ln A_s
-5373.072 0.016048 0.177486 1.056867 0.501029 1.078956 3.022956

-5410.972 0.0161 0.156035 1.016962 0.462042 1.050303 2.878407

the best fit ln like is about -5626.

Loison Hoi
Posts: 23
Joined: February 21 2006
Affiliation: McGill University

Spurious points in WMAP3 likelihood code

Post by Loison Hoi » August 02 2006

Hi,

I have checked your models; they give large, negative values of TT beam and point source corrections, which almost cancel the likelihoods from TT spectrum. This may be due to the failure of the gaussian approximations in the TT beam and point source corrections. See the topic "WMAP likelihood approximations," where I gave a model with -ln L = 5302 (k_{pivot}=0.002).

Loison Hoi
2 Aug 2006

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