Morphology and Evolution of Simulated and Optical Clusters: A Comparative Analysis (2005)
Rahman, Nurur, Krywult, Janusz, Motl, Patrick M., Flin, Piotr, Shandarin, Sergei F.
We have made a comparative study of morphological evolution in simulated DM halos and X-ray brightness distribution, and in optical clusters. Samples of simulated clusters include star formation with...
Morphological Statistics of the Cosmic Web (2004)
We report the {\em first} systematic study of the supercluster-void network in the $\Lambda$CDM concordance cosmology treating voids and superclusters on an equal footing. We study the dark matter...
Rahman, Nurur, Shandarin, Sergei F., Motl, Patrick M., Melott, Adrian L.
We have studied morphological evolution in clusters simulated in the adiabatic limit and with radiative cooling. Cluster morphology in the redshift range, $0 < z < 0.5$, is quantified by multiplicity...
Measuring Shapes of Galaxy Images II: Morphology of 2MASS Galaxies (2003)
Rahman, Nurur, Shandarin, Sergei F.
We study a sample of 112 galaxies of various Hubble types imaged in the Two Micron All Sky Survey (2MASS) in the Near-Infra Red (NIR; 1-2 $\mu$m) $J$, $H$, and $K_s$ bands. The sample contains...
Quantifying the Bull's Eye Effect (2003)
Thomas, Brian C., Melott, Adrian L., Feldman, Hume A., Shandarin, Sergei F.
We have used N-body simulations to develop two independent methods to quantify redshift distortions known as the Bull's Eye effect (large scale infall plus small scale virial motion). This effect...
Measuring Shapes of Galaxy Images I: Ellipticity and Orientation (2003)
Rahman, Nurur, Shandarin, Sergei F.
We suggest a set of morphological measures that we believe can help in quantifying the shapes of two-dimensional cosmological images such as galaxies, clusters, and superclusters of galaxies. The...
Sheth, Jatush V., Sahni, Varun, Shandarin, Sergei F., Sathyaprakash, B. S.
We present a new ansatz which can successfully be used to determine the morphological properties of the supercluster-void network. The ansatz is based on a surface modelling scheme SURFGEN, which...
Effects of Noise on Galaxy Isophotes (2002)
Rahman, Nurur, Shandarin, Sergei F.
The study of shapes of the images of objects is an important issue not only because it reveals its dynamical state but also it helps to understand the object's evolutionary history. We discuss a new...
Morphology of the Secondary CMB Anisotropies: the Key to "Smoldering" Reionization (2002)
Gnedin, Nickolay Y., Shandarin, Sergei F.
We show how the morphological analysis of the maps of the secondary CMB anisotropies can detect an extended period of ``smoldering'' reionization, during which the universe remains partially ionized....
Testing non-Gaussianity in CMB Maps by Morphological Statistic (2001)
The assumption of Gaussianity of the primordial perturbations plays an important role in modern cosmology. The most direct test of this hypothesis consists in testing Gaussianity of the CMB maps....
Morphological Measures of nonGaussianity in CMB Maps (2001)
Shandarin, Sergei F., Feldman, Hume A., Xu, Yongzhong, Tegmark, Max
We discuss the tests of nonGaussianity in CMB maps using morphological statistics known as Minkowski functionals. As an example we test degree-scale cosmic microwave background (CMB) anisotropy for...
Constraining Cosmological Models by the Cluster Mass Function (2000)
Rahman, Nurur, Shandarin, Sergei F.
We present a comparison between two observational and three theoretical mass functions for eight cosmological models suggested by the data from the recently completed BOOMERANG-98 and MAXIMA-1 cosmic...
The Cosmological Mass Function in the Zel'dovich Approximation (2000)
The Press-Schechter theory of the cosmological mass function and its modifications allow to constraint cosmological scenarios of the structure formation. Recently a few new models have been suggested...
Evidence for Filamentarity in the Las Campanas Redshift Survey (1999)
Bharadwaj, Somnath, Sahni, Varun, Sathyaprakash, B. S., Shandarin, Sergei F., Yess, Capp
We apply Shapefinders, statistical measures of `shape' constructed from two dimensional partial Minkowski functionals, to study the degree of filamentarity in the Las Campanas Redshift Survey (LCRS)....
Disentangling the Cosmic Web I: Morphology of Isodensity Contours (1999)
Schmalzing, Jens, Buchert, Thomas, Melott, Adrian L., Sahni, Varun, Sathyaprakash, B. S., Shandarin, Sergei F.
We apply Minkowski functionals and various derived measures to decipher the morphological properties of large-scale structure seen in simulations of gravitational evolution. Minkowski functionals of...
Multiple-streaming and the Probability Distribution of Density in Redshift Space (1999)
Hui, Lam, Kofman, Lev, Shandarin, Sergei F.
We examine several aspects of redshift distortions by expressing the redshift-space density in terms of the eigenvalues and orientation of the local Lagrangian deformation tensor. We explore the...
Comparison of Analytical Mass Functions with Numerical Simulations (1998)
Lee, Jounghun, Shandarin, Sergei F.
We present numerical testing results of our mass function derived in our previous paper, and compare the testing results with those of the popular Press-Schechter (PS) mass function. Two fiducial...
Minkowski Functionals and Cluster Analysis for CMB Maps (1998)
Novikov, D., Feldman, Hume A., Shandarin, Sergei F.
We suggest novel statistics for the CMB maps that are sensitive to non-Gaussian features. These statistics are natural generalizations of the geometrical and topological methods that have been...
Sathyaprakash, B. S., Sahni, Varun, Shandarin, Sergei F.
We analyse shapes of overdense regions (clusters and superclusters) in controlled N-body simulations of gravitational clustering with power law initial spectra P(k) \propto k^n, n = -3, -2, -1, 0. At...
Filaments and Pancakes in the IRAS 1.2 Jy Redshift Catalogue (1998)
Sathyaprakash, B. S., Sahni, Varun, Shandarin, Sergei F., Fisher, Karl B.
We explore shapes of clusters and superclusters in the IRAS 1.2 Jy redshift survey with three reconstructions spanning the range \beta = 0.1, 0.5, 1.0, where \beta = \Omega^{0.6}/b, b is the bias...
The Large Scale Biasing and the Primordial Gravitational Potential (1998)
Lee, Jounghun, Shandarin, Sergei F.
We modified the Press-Schechter (PS) formalism and then analytically derived a constrained mass distribution function n(M|varphi) for the regions having some specified value of the primordial...
Shapefinders: A new shape diagnostic for large scale structure (1998)
Sahni, Varun, Sathyaprakash, B. S., Shandarin, Sergei F.
We construct a set of shape-finders which determine shapes of compact surfaces (iso-density surfaces in galaxy surveys or N-body simulations) without fitting them to ellipsoidal configurations as...
Dark Matter, Discreteness and Collision Error in Cosmological N-Body Simulations (1997)
Splinter, Randall J., Melott, Adrian L., Shandarin, Sergei F.
We report on a series of tests of agreement between three types of N-body simulations: PM, P$^3$M, and Tree codes. We find good agreement in both the individual and the statistical properties only on...
The Cosmological Mass Distribution Function in the Zel'dovich Approximation (1997)
Lee, Jounghun, Shandarin, Sergei F.
An analytic approximation to the mass function for gravitationally bound objects is presented. We base on the Zel'dovich approximation to extend the Press-Schechter formalism to a nonspherical...
Fundamental Discreteness Limitations of Cosmological N-Body Clustering Simulations (1997)
Splinter, Randall J., Melott, Adrian L., Shandarin, Sergei F., Suto, Yasushi
We explore some of the effects that discreteness and two-body scattering may have on N-body simulations with ``realistic'' cosmological initial conditions. We use an identical subset of particles...
Detection of Network Structure in the Las Campanas Redshift Survey (1997)
Shandarin, Sergei F., Yess, Capp
We employ a percolation technique developed for pointwise distributions to analyze two-dimensional projections of the three northern and three southern slices in the Las Campanas Redshift Survey. One...
Modeling Gravitational Clustering without Computing Gravitational Force (1996)
Shandarin, Sergei F., Sathyaprakash, B. S.
The large-scale structure in the Universe is believed to arise out of small random density perturbations generated in the very early Universe, that are amplified by gravity. Large and usually...
Percolation Analysis of a Wiener Reconstruction of the IRAS 1.2 Jy Redshift Catalog (1996)
Yess, Capp, Shandarin, Sergei F., Fisher, Karl B.
We present percolation analyses of Wiener Reconstructions of the IRAS 1.2 Jy Redshift Survey. There are ten reconstructions of galaxy density fields in real space spanning the range $\beta= 0.1$ to...
Universality of the Network and Bubble Topology in Cosmological Gravitational Simulations (1995)
Yess, Capp, Shandarin, Sergei F.
Using percolation statistics we, for the first time, demonstrate the universal character of a network pattern in the real space, mass distributions resulting from nonlinear gravitational instability...
As galaxy redshift surveys probe deeper into the universe, they uncover ever more dramatic structures in the large-scale distribution of galaxies. In particular, the CfA2 and SSRS2 surveys to an...
Topology of the Galaxy Distribution (1995)
The history and the major results of the study of the topology of the large-scale structure are briefly reviewed. Two techniques based on percolation theory and the genus curve are discussed. The...
Fry, J. N., Melott, Adrian L., Shandarin, Sergei F.
We examine the effect of a threshold bias on the power spectrum and the bispectrum in an ensemble of numerical simulations (Gaussian initial perturbations with power law spectra P(k) \sim k^n, n=+1,...
The Evolution of Voids in the Adhesion Approximation (1994)
Sahni, Varun, Sathyaprakash, B. S., Shandarin, Sergei F.
We apply the adhesion approximation to study the formation and evolution of voids in the Universe. Our simulations -- carried out using 128$^3$ particles in a cubical box with side 128 Mpc --...