We perform a joint likelihood analysis of the power spectra of the 2dF Galaxy Redshift Survey ( 2dFGRS ) and the cosmic microwave background ( CMB ) anisotropies under the assumptions that the initial fluctuations were adiabatic , Gaussian and well described by power laws with scalar and tensor indices of n _ { s } and n _ { t } .
On its own , the 2dFGRS sets tight limits on the parameter combination \Omega _ { m } h Here h is Hubble ’ s constant H _ { 0 } in units of 100 { km } { s } ^ { -1 } { Mpc } ^ { -1 } .
The cosmic densities in baryons , cold dark matter and vacuum energy are denoted by \Omega _ { b } , \Omega _ { c } and \Omega _ { \Lambda } .
The total matter density is \Omega _ { m } = \Omega _ { b } + \Omega _ { c } and the curvature is fixed by \Omega _ { k } = 1 - \Omega _ { m } - \Omega _ { \Lambda } . , but relatively weak limits on the fraction of the cosmic matter density in baryons \Omega _ { b } / \Omega _ { m } .
The CMB anisotropy data alone set poor constraints on the cosmological constant and Hubble constant because of a ‘ geometrical degeneracy ’ among parameters .
Furthermore , if tensor modes are allowed , the CMB data allow a wide range of values for the physical densities in baryons and cold dark matter ( \omega _ { b } = \Omega _ { b } h ^ { 2 } and \omega _ { c } = \Omega _ { c } h ^ { 2 } ) .
Combining the CMB and 2dFGRS data sets helps to break both the geometrical and tensor mode degeneracies .
The values of the parameters derived here are consistent with the predictions of the simplest models of inflation , with the baryon density derived from primordial nucleosynthesis and with direct measurements of the Hubble parameter .
In particular , we find strong evidence for a positive cosmological constant with a \pm 2 \sigma range of 0.65 < \Omega _ { \Lambda } < 0.85 , completely independently of constraints on \Omega _ { \Lambda } derived from Type Ia supernovae .

Key words : Galaxy clustering , large-scale structure , cosmic microwave background- cosmology : miscellaneous .