Constraining Cosmological Parameters with CMB Measurements

Abstract

The current enthusiam to measure fluctuations in the CMB power spectrum at angular scales between 0.1 and 1 degree is largely motivated by the expectation that CMB determinations of cosmological parameters will be of unprecedented precision. In such circumstances it is important to estimate what we can already say about the cosmological parameters. In two recent papers (Lineweaver etal 1997a & 1997b) we have compiled the most recent CMB measurements, used a fast Boltzmann code to calculate model power spectra (Seljak & Zaldarriaga 1996) and, with a chi-squared analysis, we have compared the data to the power spectra from several large regions of parameter space. In the context of the flat models tested we obtain the following constraints on cosmological parameters: $Ho = 30^{+13}_{-9}$, $n=0.93^{+0.17}_{-0.16}$ and $Q=17.5^{+3.5}_{-2.5}$ uK. The n and Q values are consistent with previous estimates while the Ho result is surprisingly low.