Acoustic Oscillations in the Early Universe and Today

During its first ~100,000 years, the universe was a fully ionized plasma with a tight coupling by Thompson scattering between the photons and matter. The trade--off between gravitational collapse and photon pressure causes acoustic oscillations in this primordial fluid. These oscillations will leave predictable imprints in the spectra of the cosmic microwave background and the present day matter-density distribution. Recently, the BOOMERANG and MAXIMA teams announced the detection of these acoustic oscillations in the cosmic microwave background (observed at redshift ~1000). Here, we compare these CMB detections with the corresponding acoustic oscillations in the matter-density power spectrum (observed at redshift ~0.1). These consistent results, from two different cosmological epochs, provide further support for our standard Hot Big Bang model of the universe.Comment: To appear in the journal Science. 6 pages, 1 color figur

Nearest neighbor vector analysis of sdss dr5 galaxy distribution

We present the Nearest Neighbor Distance (NND) analysis of SDSS DR5 galaxies. We give NND results for observed, mock and random sample, and discuss the differences. We find that the observed sample gives us a significantly stronger aggregation characteristic than the random samples. Moreover, we investigate the direction of NND and find that the direction has close relation with the size of the NND for the observed sample.Comment: Natural Science, Vol.5, No.1 in January 201

Dense Galactic Superclusters Add New Structural Details to the Universe

At the American Astronomical Society meeting in Austin, Texas, Thursday, January 7, 1999, astronomers David Batuski and Chris Miller of the University of Maine, presented evidence of two relatively rare types of galaxy superclusters in a single colossal complex in the southern part of the constellation Aquarius. The complex consists of two long filaments, one of which is the longest such object yet seen, and a dense knot of clusters. These findings add significantly to the emerging picture of large-scale structure in the present-day universe and provide some well-defined examples of structure that must be explained by processes in the fireball of the Big Bang. Future analysis of the knot of clusters, when studied in detail with three other similar clumps of clusters, may prove that some vast objects may be collapsing within our otherwise expanding universe

Discovery of Extreme Examples of Superclustering in Aquarius

We report the discovery of two highly extended filaments and one extremely high density knot within the region of Aquarius. The supercluster candidates were chosen via percolation analysis of the Abell and ACO catalogs and include only the richest clusters (R >= 1). The region examined is a 10x45 degree strip and is now 87% complete in cluster redshift measurements to mag_10 = 18.3. In all, we report 737 galaxy redshifts in 46 cluster fields. One of the superclusters, dubbed Aquarius, is comprised of 14 Abell/ACO clusters and extends 110h^-1Mpc in length only 7 degrees off the line-of-sight. On the near-end of the Aquarius filament, another supercluster, dubbed Aquarius-Cetus, extends for 75h^-1Mpc perpendicular to the line-of-sight. After fitting ellipsoids to both Aquarius and Aquarius-Cetus, we find axis ratios (long-to- midlength axis) of 4.3 for Aquarius and 3.0 for Aquarius-Cetus. We fit ellipsoids to all N>=5 clumps of clusters in the Abell/ACO measured-z cluster sample. The frequency of filaments with axis ratios >=3.0 (~20%) is nearly identical with that found among `superclusters' in Monte Carlo simulations of random and random- clumped clusters, however, so the rich Abell/ACO clusters have no particular tendency toward filamentation. The Aquarius filament also contains a `knot' of 6 clusters at Z ~0.11, with five of the clusters near enough togeteher to represent an apparent overdensity of 150. There are three other R >= 1 cluster density enhancements similar to this knot at lower redshifts: Corona Borealis, the Shapely Concentration, and another grouping of seven clusters in Microscopium. All four of these dense superclusters appear near the point of breaking away from the Hubble Flow, and some may now be in collapse, but there is little evidence of any being virialized.Comment: 45 pages (+ e-tables), 7 figures, AASTeX Accepted for Publication in Ap

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

We present a joint analysis of the power spectra of density fluctuations from three independent cosmological redshift surveys; the PSCz galaxy catalog, the APM galaxy cluster catalog and the Abell/ACO cluster catalog. Over the range 0.03 <= k <= 0.15 h/Mpc,the amplitudes of these three power spectra are related through a simple linear biasing model with b = 1.5 and b = 3.6 for Abell/ACO versus APM and Abell/ACO versus the PSCz respectively. Furthermore, the shape of these power spectra are remarkably similar despite the fact that they are comprised of significantly different objects (individual galaxies through to rich clusters). Individually, each of these surveys show visible evidence for ``valleys'' in their power spectra. We use a newly developed statistical technique called the False Discovery Rate, to show that these ``valleys'' are statistically significant. One favored cosmological explanation for such features in the power spectrum is the presence of a non-negligible baryon fraction (Omega_b/Omega_m) in the Universe which causes acoustic oscillations in the transfer function of adiabatic inflationary models. We have performed a maximum-likelihood marginalization over four important cosmological parameters of 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 consistent with the favored values of these cosmological parameters from the recent Cosmic Microwave Background (CMB) experiments. This agreement strongly suggests that we have detected baryonic oscillations in the power spectrum of matter at a level expected from a Cold Dark Matter model normalized to fit these CMB measurements.Comment: 13 pages, 4 figures, ApJ in press. Typos fixed. Replaced Figure 4 with improved versio

The dynamics of Abell 2634

We have amassed a large sample of velocity data for the cluster of galaxies Abell 2634 which contains the wide-angle tail (WAT) radio source 3C 465. Robust indicators of location and scale and their confidence intervals are used to determine if the cD galaxy, containing the WAT, has a significant peculiar motion. We find a cD peculiar radial velocity of 219 plus or minus 98 km s(exp -1). Further dynamical analyses, including substructure and normality tests, suggest that A 2634 is an unrelaxed cluster whose radio source structure may be bent by the turbulent gas of a recent cluster-subcluster merger