Cosmological Parameters from the 2003 flight of BOOMERANG

TL;DR

This study analyzes the 2003 BOOMERANG flight data, including polarization, to constrain cosmological parameters within a flat ΛCDM framework and to explore extensions such as running spectral index, curvature, tensors, massive neutrinos, dark energy w, and isocurvature admixtures. It employs two independent data pipelines, Xfaster likelihoods, and Bayesian MCMC (CosmoMC) on top of CAMB, integrating CMB data with SDSS/2dFGRS LSS information and SNIa/H_0 priors. The results show BOOMERANG data are consistent with WMAP and other CMB experiments, delivering precise constraints on θ and σ_8 and revealing modest support for small running, near-flat curvature, and a dark energy equation of state compatible with a cosmological constant. Polarization measurements are consistent with the adiabatic paradigm, while isocurvature components are tightly constrained but not entirely excluded, underscoring polarization’s role in breaking degeneracies and guiding future analyses.

Abstract

We present the cosmological parameters from the CMB intensity and polarization power spectra of the 2003 Antarctic flight of the BOOMERANG telescope. The BOOMERANG data alone constrains the parameters of the $Λ$CDM model remarkably well and is consistent with constraints from a multi-experiment combined CMB data set. We add LSS data from the 2dF and SDSS redshift surveys to the combined CMB data set and test several extensions to the standard model including: running of the spectral index, curvature, tensor modes, the effect of massive neutrinos, and an effective equation of state for dark energy. We also include an analysis of constraints to a model which allows a CDM isocurvature admixture.

Figures (10)

• Figure 1: The B03 bandpowers used in this analysis. We have included the total intensity TT, polarization EE and BB, and cross correlation TE spectra. The EB and TB spectra are excluded from this parameter analysis. The solid/black curve is the previous concordance model, a best fit to WMAP(first-year)+CBI+ACBAR data from http://lambda.gsfc.nasa.gov/product/map/, with ($\Omega_b h^2, \Omega_c h^2, n_{\rm s}(k=0.05), \exp(-2\tau), A(k=0.05), h$) = (0.0224, 0.111, 0.958, 0.802, 0.739, 0.720). The yellow/dotted curve is the CMBall (Table \ref{['tab:cmball']})+B03 maximum likelihood $\Lambda$CDM model from this analysis with (slightly different parameterization--see text), ($\Omega_b h^2, \Omega_c h^2, n_{\rm s}(k=0.05), \tau, \ln(10^{10} A_{\rm s}(k=0.05)), \theta$) = (0.0228, 0.108, 0.959, 0.138, 3.12, 1.04).
• Figure 2: Median values obtained from the marginalized probability for each parameter for the baseline, standard model. The errors bars represent the 68% confidence interval. The 95% upper limit is given for the case of $\tau$ for B03 data alone. The following flat weak priors are imposed (as outlined in Table \ref{['tab:weakpriors']}): $0.5 \leq n_{s} \leq 1.5$; $2.7 \leq \ln(10^{10} A_{s}) \leq 4.0$; $0.005 \leq \Omega_{b}h^{2} \leq 0.1$; $0.01 \leq \Omega_{c}h^{2} \leq 0.99$; $0.5 \leq \theta \leq 10.0$; and $0.01 \leq \tau \leq 0.8$. Additional weak priors restrict the age of the universe to $10 \text{Gyr} \leq \text{age} \leq 20 \text{Gyr}$ and the expansion rate to $45 \leq H_0 \leq 90$. Our baseline CMBall+B03+LSS result is fairly insensitive to $\delta b_g$ and we have chosen for this case the less restrictive flat, uniform prior in $b_g^2$.
• Figure 3: Constraints on $A_{\rm s} e^{-2\tau}$ versus $\theta$. Inner contours represent 68% likelihood regions and outer contours 95% likelihood regions. The peak position characterization parameter $\theta$ is best the determined parameter in cosmology, $1.045 \pm 0.004$, from the CMBall+B03 data set. We find that the B03 TT data does particularly well at constraining both the peak pattern and the combined $A_{\rm s} e^{-2\tau}$ amplitude parameter. The constraint from WMAP alone on $A_{\rm s}$ is better than that from B03. The agreement between the B03 pol and B03 TT data is consistent with the basic inflation picture.
• Figure 4: Marginalized one-dimensional distributions for the baseline model parameters for the data combinations WMAP only (black/dotted), WMAP + B03 (green/solid), CMBall + B03 (blue/dashed), and CMBall + B03 + LSS (red/dash-dotted). The curves are each normalized by their peak values. All distributions are derived from chains run with the weak set of external, uniform priors shown in Table \ref{['tab:weakpriors']}. The LSS data consists of the 2dFGRS and SDSS redshift surveys (with a flat $b_g^2$ prior imposed). The most significant impact of the B03 data is on ${\sigma}_8$. Moreover, the ${\sigma}_8$ constraint from CMB data alone is quite strong, with the addition of LSS data having little effect.
• Figure 5: Marginalized one-dimensional distributions for the ${n_{\rm run}}$ parameter for the baseline + running index model. Weak priors imposed are those outlined in Table \ref{['tab:weakpriors']}. The running index parameter is restricted to lie between -0.3 and 0.3. Application of the HST prior on $H_0$ slightly reduces the significance of a running index.