The last tango before MAP

Here's a combination of all data as of December 2002 (incl. Acbar + new Boom) taking into account calibration and beam errors (click on it for ps). Curve shows best model fit for CMB+LSS data.
Here are text files with the corresponding data, window functions and correlation matrix. (These files and the plot above include the new Acbar and Boomerang (Ruhl et al MADCAP) measurements. If you for some reason want the pre-Acbar results, here's the data, window functions and correlation matrix.) The window function file above contains 28 columns, giving the window functions W_l for each of the 28 band power measurements with the convention
(dT)^2 = sum W_l (dT_l)^2 = sum l(l+1) W_l C_l/2 pi.
Note that this differs from the traditional definition by a factor of l - it's more approptiate to think of the band power as an average on a linear plot rather than on a log-plot now that we're all plotting small-scale CMB data with a linear l-axis. Also, note that some of these window functions go slightly negative, and that that's OK. Note that the file gives not the covariance matrix but the dimensionless correlation matrix R, which is related to the covariance matrix C by
C_ij = R_ij sigma_i sigma_j.
To test a model against this data, put the first 2000 values of dT_l^2 = l(l+1) C_l/2 pi into a vector c and compute
chi2 = (q-Wc)^t C^{-1} (q-Wc),
where q is our vector of 28 data points and W is our window matrix. You'll find more data details and links here. Update with Acbar and ultimate BOOM coming hopefully later today (02/12/20).

The last stand before MAP: cosmological parameters from lensing, CMB and galaxy clustering

Please click here to download our paper.
Click here if you are interested in other research of mine. 


Xiaomin Wang, Max Tegmark, Bhuvnesh Jain, Matias Zaldarriaga


Cosmic shear measurements have now improved to the point where they deserve to be trea ted on par with CMB and galaxy clustering data for cosmological parameter analysis, us ing the full measured aperture mass variance curve rather than a mere phenomenological parametrization thereof. We perform a detailed 9-parameter analysis of recent lensing (RCS), CMB (up to Archeops) and galaxy clustering (2dF) data, both separately and joi ntly. CMB and 2dF data are consistent with a simple flat adiabatic scale-invariant mod el with Omega_Lambda=0.72+/-0.09, omega_cdm=0.115+/- 0.013, omega_b=0.0024+/-0.003, an d a hint of reionization around z~8. Lensing helps further tighten these constraints, but reveals tension regarding the power spectrum normalization: including the RCS surv ey results raises sigma8 significantly and forces other parameters to uncomfortable va lues. Indeed, sigma8 is emerging as the currently most controversial cosmological para meter, and we discuss possible resolutions of this sigma8 problem. We also comment on the disturbing fact that most recent analyses (including this one) obtain error bars s maller than the Fisher matrix bound. We produce a CMB power spectrum combining all exi sting experiments, and using it for a "MAP versus world" comparison next month will pr ovide a powerful test of how realistic the error estimates have been in the cosmology community.

Reference info:

Submitted to Phys. Rev. D
Return to my home page
This page was last modified December 20, 2002.