Page 1 of 1

Spurious points in WMAP3 likelihood code

Posted: August 02 2006
by Michael Bridges
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.

Spurious points in WMAP3 likelihood code

Posted: August 02 2006
by Loison Hoi
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