ar X iv : a st ro - p h / 97 10 30 3 v 1 2 8 O ct 1 99 7 Can Baryonic Features

We assess the possibility that baryonic acoustic oscillations in adiabatic models may explain the observations of excess power in large-scale structure on 100h Mpc scales. The observed location restricts models to two extreme areas of parameter space. In either case, the baryon fraction must be large (Ωb/Ω0 ∼> 0.3) to yield significant features. The first region requires Ω0 ∼< 0.2h to match the location, implying large blue tilts (n ∼> 1.4) to satisfy cluster abundance constraints. The power spectrum also continues to rise toward larger scales in these models. The second region requires Ω0 ≈ 1, implying Ωb well out of the range of big bang nucleosynthesis constraints; moreover, the peak is noticeably wider than the observations suggest. Testable features of both solutions are that they require moderate reionization and thereby generate potentially observable (∼ 1μK) large-angle polarization, as well as sub-arc-minute temperature fluctuations. In short, baryonic features in adiabatic models may explain the observed excess only if currently favored determinations of cosmological parameters are in substantial error or if present surveys do not represent a fair sample of 100h Mpc structures. Alfred P. Sloan Fellow