Antony Lewis
Joined: 23 Sep 2004 Posts: 1333 Affiliation: University of Sussex
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Posted: December 06 2004 |
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I'm not sure when I'm going to get round to writing up the conclusions of this. Here's a summary.
Using the lensed Cl seems to work fine for parameter estimation as long as you compute the theoretical result accurately. In particular the 2nd-order perturbative result (e.g. astro-ph/0001303) is not accurate enough. Here's a comparison with the correct result
Red is the 2nd order result, and biases parameters for Planck. The blue result is that of astro-ph/9505109, which is actually pretty much accurate enough for Planck. The very accurate 'correct' result was generated using the Nov 2004 version of CAMB using a new full-sky generalization of the result in astro-ph/9505109 (work with Anthony Challinor).
Using the accurate Cl calculation, for a typical idealized Planck-like simulation I get parameter constraints for a vanilla model like this:
Here black is analysing the lensed sky with the lensed Cl, red is analysing the unlensed sky with the unlensed Cl, and blue is the wrong result if you analyse the lensed sky but neglect lensing in the Cl calculation. The lensed results neglects non-gaussianity of the lensed field.
[The simulation input model had ns = 0.99, As = 2.5×10 - 9, Ωbh2 = 0.022, Ωbh2 = 0.12, τ = 0.15 and h = 0.72]. |
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