*Astron. Astrophys. 329, 799-808 (1998)*
## Cosmic microwave background observations:
implications for Hubble's constant and the spectral parameters *n*
and *Q* in cold dark matter critical density universes
**
Charles H. Lineweaver **^{ 1} and
Domingos Barbosa ^{ 1, 2}
^{1} Observatoire astronomique de Strasbourg, U.L.P., F-67000
Strasbourg, France.
^{2} Centro de
Astrofsica da U.P., Rua do
Campo Alegre 823, PT-4150 Porto, Portugal.
*Received 2 December 1996 / Accepted 21 May 1997*
**Abstract**
Recent cosmic microwave background (CMB) measurements over a large
range of angular scales have become sensitive enough to provide
interesting constraints on cosmological parameters within a restricted
class of models. We use the CMB measurements to study inflation-based,
cold dark matter (CDM) critical density universes. We explore the
4-dimensional parameter space having as free parameters, Hubble's
constant , baryonic fraction
, the spectral slope of scalar perturbations
*n* and the power spectrum quadrupole normalization *Q*. We
calculate minimization values and likelihood
intervals for these parameters. Within the models considered, a low
value for the Hubble constant is preferred: . The
baryonic fraction is not as well-constrained by the CMB data:
. The power spectrum slope is
. The power spectrum normalization is
K. The error bars on each parameter are
approximately and are for the case where the
other 3 parameters have been marginalized. If we condition on
we obtain the normalization
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-
models are consistent with Big Bang
nucleosynthesis, cluster baryonic fractions, the large-scale
distribution of galaxies and the ages of globular clusters; although
in disagreement with direct determinations of the Hubble constant.
**Key words:** cosmic microwave
background
cosmology:
observations
theory
*Send offprint requests to:* Charley Lineweaver,
charley@edwin.phys.unsw.edu.au
### Contents
© European Southern Observatory (ESO) 1998
Online publication: December 16, 1997
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