Possible detection of baryonic fluctuations in the large-scale structure power spectrum

We present a joint analysis of the power spectra of density fluctuations fr om three independent cosmological redshift surveys : the IRAS Point Source redshift catalog (PSCz) galaxy survey, the Automated Plate Measuring Machin e (APM) galaxy cluster catalog, and the Abell/ACO cluster survey. Over the range 0.03 h Mpc(-1) less than or equal to k less than or equal to 0.15 h M pc(-1), the amplitudes of these three power spectra are related through a s imple linear-biasing model with b = 1.5 and b = 3.6 for Abell/ACO versus AP M and Abell/ACO versus PSCz, respectively. Furthermore, the shape of these power spectra are remarkably similar despite the fact that they are compris ed of significantly different objects (individual galaxies through to rich clusters). Individually, each of these surveys shows visible evidence for " valleys" in their power spectra-i.e., departures from a smooth featureless spectrum-at similar wavenumbers. We use a newly developed statistical techn ique called the false discovery rate to show that these valleys are statist ically significant. One favored cosmological explanation for such features in the power spectrum is the presence of a nonnegligible baryon fraction in the universe, which causes acoustic oscillations in the transfer function of adiabatic inflationary models. We have performed a maximum likelihood ma rginalization over four important cosmological parameters of this model (Om ega (m), Q(b), n(s), and H-0). We use a prior on H-0 = 69 +/- 15 and find O mega (m) h(2) = 0.12(-0.03)(+0.02), Omega (b) h(2) = 0.029(-0.015)(+0.011), and n(s) = 1.08(-0.20)(+0.17) (2 sigma confidence limits), which are fully consistent with the favored values of these cosmological parameters from t he recent cosmic microwave background (CMB) experiments. This agreement str ongly suggests that we have detected baryonic oscillations in the power spe ctrum of matter at a level expected from a cold dark matter model normalize d to fit these CMB measurements.