TESTING DEPROJECTION ALGORITHMS ON MOCK ANGULAR CATALOGS - EVIDENCE FOR A BREAK IN THE POWER SPECTRUM

We produce mock angular catalogues from simulations with different ini tial power spectra to test methods that recover measures of clustering in three dimensions, such as the power spectrum, variance and higher order cumulants. We find that the statistical properties derived from the angular mock catalogues are in good agreement with the intrinsic c lustering in the simulations. In particular, we concentrate on the det ailed predictions for the shape of the power spectrum, P(k). We find t hat there is good evidence for a break in the galaxy P (k) at scales i n the range 0.02<k<0.06 h Mpc(-1), using an inversion technique applie d to the angular correlation function measured from the APM Galaxy Sur vey. For variants on the standard cold dark matter (CDM) model, a fit at the location of the break implies Omega h=0.45+/-0.10, where Omega is the ratio of the total matter density to the critical density, and Hubble's constant is parametrized as H-0=100 h km s(-1) Mpc(-1). On sl ightly smaller, though still quasi-linear scales, there is a feature i n the APM power spectrum where the local slope changes appreciably, wi th the best match to CDM models obtained for Omega similar or equal to 0.2. Hence the location and narrowness of the break in the APM power spectrum combined with the rapid change in its slope on quasi-linear s cales cannot be matched by any variant of CDM, including models that h ave a nonzero cosmological constant or a tilt to the slope of the prim ordial P (k). These results are independent of the overall normalizati on of the CDM models or any simple bias that exists betwen the galaxy and mass distributions.