Large Scale Structure in an Era of Precision CMB Measurements

The advent of high signal-to-noise cosmic microwave background (CMB) anisotropy experiments now allow detailed studies on the statistics related to temperature fluctuations. The existence of acoustic oscillations in the anisotropy power spectrum is now established with the clear detection of the first, and to a lesser confidence the second and the third, peak. Beyond the acoustic peak structure associated with CMB photon temperature fluctuations, we study the possibility for an observational detection of oscillations in the large scale structure (LSS) matter power spectrum due to baryons. We also suggest a new cosmological test using the angular power spectrum of dark matter halos, or clusters of galaxies detected via wide-field surveys of the large scale structure. The standard rulers of the proposed test involve overall shape of the matter power spectrum and baryon oscillation peaks in projection. The test allows a measurement of the angular diameter distance as a function of redshift, similar to the distance to the last scattering surface from the first acoustic peak in the temperature anisotropy power spectrum. The simultaneous detection of oscillations in both photons and baryons will provide a strong, and a necessary, confirmation of our understanding related to the physics during the recombination era. The proposed studies can be carried out with a combined analysis of CMB data from missions such as the MAP and the large scale structure data from missions such as the DUET. 1 Oscillations in CMB The cosmic microwave background (CMB) is now a well known probe of the early universe. The temperature fluctuations in the CMB, especially the so-called acoustic peaks in the angular power spectrum of CMB anisotropies, capture the physics of primordial photon-baryon fluid undergoing oscillations in the potential wells of the dark matter [1]. The associated physics — involving the evolution of a single photon-baryon fluid under Compton scattering and gravity — are both simple and linear, and many aspects of it have been discussed in the literature since the early 1970s [2]. The gravitational redshift contribution at large angular scales [3] and the photon-diffusion damping at small angular scales [4] complete this description. By now, there are at least five independent detections of the first, and possibly the second and the third, acoustic peak in the anisotropy power spectrum [5,6]. We summarize these results in figure 1. Given the variety of experiments that are either collecting data or reducing data that were recently collected, more detections that extend to higher peaks are soon expected. The NASA’s