COSMIC MICROWAVE BACKGROUND OBSERVATIONS - IMPLICATIONS FOR HUBBLES CONSTANT AND THE SPECTRAL PARAMETER-N AND PARAMETER-Q IN COLD DARK-MATTER CRITICAL DENSITY UNIVERSES
Ch. Lineweaver et D. Barbosa, COSMIC MICROWAVE BACKGROUND OBSERVATIONS - IMPLICATIONS FOR HUBBLES CONSTANT AND THE SPECTRAL PARAMETER-N AND PARAMETER-Q IN COLD DARK-MATTER CRITICAL DENSITY UNIVERSES, Astronomy and astrophysics, 329(3), 1998, pp. 799-808
Recent cosmic microwave background (CMB) measurements over a large ran
ge of angular scales have become sensitive enough to provide interesti
ng constraints on cosmological parameters within a restricted class of
models. We use the CMB measurements to study inflation-based, cold da
rk matter (CDM) critical density universes. We explore the 4-dimension
al parameter space having as free parameters, Hubble's constant H-o, b
aryonic fraction Omega b, the spectral slope of scalar perturbations n
and the power spectrum quadrupole normalization Q. We calculate chi(2
) minimization values and likelihood intervals for these parameters. W
ithin the models considered, a low value for the Hubble constant is pr
eferred: H-o = 30(-7)(+18) km s(-1) Mpc(-1). The baryonic fraction is
not as well-constrained by the CMB data: Omega(b) = 0.07(-0.07)(+0.24)
. The power spectrum slope is n = 0.91(-0.12)(+0.20). The power spectr
um normalization is Q = 18 +/- 2.5 mu K. The error bars on each parame
ter are approximately 1 sigma and are for the case where the other 3 p
arameters have been marginalized. If we condition on n = 1 we obtain t
he normalization Q = 17 +/- 1.0 mu K. The permitted regions of the 4-D
parameter space are presented in a series of 2-D projections. In the
context of the CDM critical density universes considered here, current
CMB data favor a low value for the Hubble constant. Such low-H-o mode
ls are consistent with Big Bang nucleosynthesis, cluster baryonic frac
tions, the large-scale distribution of galaxies and the ages of globul
ar clusters; although in disagreement with direct determinations of th
e Hubble constant.