Possible Detection of Baryonic Fluctuations in the Large‐Scale Structure Power Spectrum

We present a joint analysis of the power spectra of density fluctuations fromthree independent cosmological redshift surveys; the PSCz galaxy catalog, theAPM galaxy cluster catalog and the Abell/ACO cluster catalog. Over the range0.03 <= k <= 0.15 h/Mpc,the amplitudes of these three power spectra are relatedthrough a simple linear biasing model with b = 1.5 and b = 3.6 for Abell/ACOversus APM and Abell/ACO versus the PSCz respectively. Furthermore, the shapeof these power spectra are remarkably similar despite the fact that they arecomprised of significantly different objects (individual galaxies through torich clusters). Individually, each of these surveys show visible evidence for``valleys'' in their power spectra. We use a newly developed statisticaltechnique called the False Discovery Rate, to show that these ``valleys'' arestatistically significant. One favored cosmological explanation for suchfeatures in the power spectrum is the presence of a non-negligible baryonfraction (Omega_b/Omega_m) in the Universe which causes acoustic oscillationsin the transfer function of adiabatic inflationary models. We have performed amaximum-likelihood marginalization over four important cosmological parametersof this model (Omega_m, Omega_b, n_s, H_o). We use a prior on H_0 = 69(+/-15),and find Omega_mh^2 = 0.12(+0.03/-0.02), Omega_bh^2 =0.029(+0.011/-0.015), n_s= 1.08^(+0.17/-0.20) (2 sigma confidence limits) which are fully consistentwith the favored values of these cosmological parameters from the recent CosmicMicrowave Background (CMB) experiments. This agreement strongly suggests thatwe have detected baryonic oscillations in the power spectrum of matter at alevel expected from a Cold Dark Matter model normalized to fit these CMBmeasurements.Comment: 13 pages, 4 figures, ApJ in press. Typos fixed. Replaced Figure 4 with improved versio