[en] Standard model of Big Bang cosmology is surveyed and explained in an elementary manner. Some unsolved problems, e.g. missing masses on galactic and cosmological scales, the unexplained size of the largest objects of the Universe, the galaxy superclusters are reviewed. These problems can be solved by assuming the neutrino having nonvanishing rest mass of about 30 eV. The main events of the development of a neutrino-dominated Universe are summarized. Decoupling and cooling, i.e. stopping of neutrinos give the possibility of formation of neutrino superstars, with their gravitational potential wells serving as birth-places of galaxy superclusters. The value of neutrino mass, predicted by the authors based on cosmological considerations ten years ago, was verified recently by laboratory experiments. (D.Gy.)

[en] Extreme value statistics is applied to the distribution of galaxy luminosities in the Sloan Digital Sky Survey. We analyze the DR8 Main Galaxy Sample (MGS), as well as the luminous red galaxies (LRGs). Maximal luminosities are sampled from batches consisting of elongated pencil beams in the radial direction of sight. For the MGS, results suggest a small and positive tail index ξ, effectively ruling out the possibility of having a finite maximum cutoff luminosity, and implying that the luminosity distribution function may decay as a power law at the high-luminosity end. Assuming, however, ξ = 0, a non-parametric comparison of the maximal luminosities with the Fisher-Tippett-Gumbel distribution (limit distribution for variables distributed by the Schechter fit) indicates a good agreement provided that uncertainties arising from both the finite batch size and the batch-size distribution are accounted for. For a volume-limited sample of LRGs, results show that they can be described as being the extremes of a luminosity distribution with an exponentially decaying tail, provided that the uncertainties related to batch-size distribution are taken care of.

[en] In view of future high-precision large-scale structure surveys, it is important to quantify the percent and subpercent level effects in cosmological N-body simulations from which theoretical predictions are drawn. One such effect involves deciding whether to zero all modes above the one-dimensional Nyquist frequency, the so-called “corner” modes, in the initial conditions. We investigate this effect by comparing power spectra, density distribution functions, halo mass functions, and halo profiles in simulations with and without these modes. For a simulation with a mass resolution of $m_p\sim <!--\; ???\; -->{10}^{11}$ $h^{-<!--\; ???\; -->1}{M}_{\odot <!--\; ???\; -->}$, we find that at $z><!--\; >\; -->6$, the difference in the matter power spectrum is large at wavenumbers above ∼80% of $k_{\mathrm{N}\mathrm{y}}$, reducing to below 2% at all scales by $z\sim <!--\; ???\; -->3$. Including corner modes results in a better match between low- and high-resolution simulations at wavenumbers around the Nyquist frequency of the low-resolution simulation, but the effect of the corner modes is smaller than the effect of particle discreteness. The differences in mass functions are 3% for the smallest halos at z = 6 for the $m_p\sim <!--\; ???\; -->{10}^{11}$ $h^{-<!--\; ???\; -->1}{M}_{\odot <!--\; ???\; -->}$ simulation, but we find no significant difference in the stacked profiles of well-resolved halos at $z⩽<!--\; ???\; -->6$. Thus removing power at $|\mathit{k}|><!--\; >\; -->k_{\mathrm{N}\mathrm{y}}$ in the initial conditions of cosmological simulations has a small effect on small scales and high redshifts, typically below a few percent.

[en] We will discuss the challenges of visualizing large cosmological datasets. These include observational issues such as the masks and incomplete nature of the survey volume, cosmological issues such as redshift distortions and the difficulty of visualizing datasets that span cosmological epochs, as well as the inherent visualization challenges in presenting dense three-dimensional (3D) datasets. Two case studies will be presented. The first will feature the identification of filamentary structures in the large scale distribution of galaxies. The second case study will feature visualizations of the correlations between quasar absorption line systems and luminous red galaxies. Finally, we will give an overview of our visualization work-flow which features the use of the open-source 3D modeling program Blender.

[en] Under the unified model for active galactic nuclei (AGNs), narrow-line (Type 2) AGNs are, in fact, broad-line (Type 1) AGNs but each with a heavily obscured accretion disk. We would therefore expect the optical continuum emission from Type 2 AGNs to be composed mainly of stellar light and nonvariable on the timescales of months to years. In this work we probe the spectroscopic variability of galaxies and narrow-line AGNs using the multiepoch data in the Sloan Digital Sky Survey Data Release 6. The sample contains 18,435 sources for which there exist pairs of spectroscopic observations (with a maximum separation in time of ∼700 days) covering a wavelength range of 3900-8900 A. To obtain a reliable repeatability measurement between each spectral pair, we consider a number of techniques for spectrophotometric calibration resulting in an improved spectrophotometric calibration of a factor of 2. From these data we find no obvious continuum and emission-line variability in the narrow-line AGNs on average-the spectroscopic variability of the continuum is 0.07 ± 0.26 mag in the g band and, for the emission-line ratios log₁₀([N II]/Hα) and log₁₀([O III]/Hβ), the variability is 0.02 ± 0.03 dex and 0.06 ± 0.08 dex, respectively. From the continuum variability measurement we set an upper limit on the ratio between the flux of the varying spectral component, presumably related to AGN activities, and that of the host galaxy to be ∼30%. We provide the corresponding upper limits for other spectral classes, including those from the BPT diagram, eClass galaxy classification, stars, and quasars.