Ω FROM THE COBE ‐DMR ANISOTROPY MAPS

The angular correlation of the Cosmic Microwave Background maps can be used to constrain galaxy formation scenarios. Low-density (Q) models can generate inflationary epoch adiabatic density perturbations in open universes (Lyth & Stewart 19901, Ratra & Peebles 1994' ). Other low-R models have power spectra as given by simple prescriptions. The pioniering calculation of Wilson ( 1983)3 assumed a power law in wavenumber while Kamionkowski and Spergel (1994)4 considered power laws in spatial volume and scalar spatial Laplacian eigenvalue. Here we consider a low-R model where the cosmological constant is zero. We assume a cold dark matter cosmogony with baryon density QB = 0.03 and h = 0.5 and as primordial spectrum, we will use the &-risonZeldovich one where P ( k ) a: k. At angular scales greater than (2R'f')o a generalized formula for nonflat universes can be obtained (Anile and Motta 1976', Abbott and Schaefer 19866, Traschen and Eardley 1986', Gouda et al. 1991') which gives the CMB anisotropy in terms of gravitational potential fluctuations at recombination with an integrated time-varying gravitational potential along the photon trajectory that depends on curvature. Recently low-R models and CMB anisotropies have used a multipole expansion for the temperature anisotropies AT/T = qm &,. To study the COBE cross-correlation data only multipoles up to 30 are considered (Sugiyama & Silk 1994', Kamionkowski et al. 1994"). We are interested to test with the most simple model (a CDM cosmogony with a HZ primordial spectrum) to what extend the COBEDMR two-year data imply or not the flatness of the universe, i.e. R = 1. To do this, we used two-year data from the most sensitive radiometers (53 and 90 G H z ) and we obtained the limits on Qrm.-p~ and fl imposed by the cross-correlation of the two maps.