Showing papers by "Anatoly Klypin published in 1993"
TL;DR: In this article, high-resolution particle-mesh (PM) N-body simulations of structure formation in an O(1) cosmological model with a mixture of Cold plus Hot Dark Matter (C+HDM) have been presented.
Abstract: We report results from high-resolution particle-mesh (PM) N-body simulations of structure formation in an $\Omega=1$ cosmological model with a mixture of Cold plus Hot Dark Matter (C+HDM) having $\Omega_{\rm cold}=0.6$, $\Omega_
u=0.3$, and $\Omega_{\rm baryon}=0.1$. We present analytic fits to the C+HDM power spectra for both cold and hot ($
u$) components, which provide initial conditions for our nonlinear simulations. In order to sample the neutrino velocities adequately, these simulations included six times as many neutrino particles as cold particles. Our simulation boxes were 14, 50, and 200~Mpc cubes (with $H_0=50$ km s$^{-1}$ Mpc$^{-1}$); we also did comparison simulations for Cold Dark Matter (CDM) in a 50~Mpc box. C+HDM with linear bias factor $b=1.5$ is consistent both with the COBE data and with the galaxy correlations we calculate. We find the number of halos as a function of mass and redshift in our simulations; our results for both CDM and C+HDM are well fit by a Press-Schechter model. The number density of galaxy-mass halos is smaller than for CDM, especially at redshift $z>2$, but the numbers of cluster-mass halos are comparable. We also find that on galaxy scales the neutrino velocities and flatter power spectrum in C+HDM result in galaxy pairwise velocities that are in good agreement with the data, and about 30\% smaller than in CDM with the same biasing factor. On scales of several tens of Mpc, the C+HDM streaming velocities are considerably larger than CDM. Thus C+HDM looks promising as a model of structure formation.
171 citations
TL;DR: In this paper, high-resolution particle-mesh (PM) N-body simulations of structure formation in an Ω=1 cosmological model with a mixture of cold plus hot dark matter (C+HDM) having Ω cold = 0.6, Ω ν =0.3, and Ω baryon = 1.1.
Abstract: We report results from high-resolution particle-mesh (PM) N-body simulations of structure formation in an Ω=1 cosmological model with a mixture of cold plus hot dark matter (C+HDM) having Ω cold =0.6, Ω ν =0.3, and Ω baryon =0.1. We present analytic fits to the C+HDM power spectra for both cold and hot (neutrino) components, which provide initial conditions for our nonlinear simulations. In order to sample the neutrino velocities adequately, these simulations included 6 times as many neutrino particles as cold particles. Our simulations boxes were 14, 50, and 200 Mpc cubes (with H 0 =50 km s −1 Mpc −1 ); we also did comparison simulations for cold dark matter (CDM) in a 50 Mpc box
162 citations
TL;DR: In this article, the authors present results of new high resolution simulations of CHDM and CDM and compare these two models in redshift space in a careful and consistent way, and find that CHDM remains a promising model, with for example $v_{\rmgr}(045) \approx 125 \pm 25 \kms$ in agreement with the CfA data.
Abstract: This letter presents results of new high resolution $\Omega=1$ Cold + Hot Dark Matter (CHDM) and Cold Dark Matter (CDM) simulations Properties of groups in these simulations reflect the lower small-scale velocities and the greater tendency to form distinct filaments on both small and large scales in CHDM as compared to CDM The fraction of galaxies in groups and the median group rms velocity are found to be powerful discriminators between models We combine these two features into a very robust statistic, median group rms velocity $v_{\rm gr}(f_{\rm gr})$ as a function of the fraction $f_{\rm gr}$ of galaxies in groups Using this statistic, we compare ``observed'' simulations to CfA data in redshift space in a careful and consistent way We find that CHDM remains a promising model, with for example $v_{\rmgr}(045) \approx 125 \pm 25 \kms$ in agreement with the CfA data, while CDM with bias b=10 (COBE-compatible) or b=15, both giving $v_{\rm gr}(045) \approx 400 \pm 25 \kms$, can be virtually ruled out Using median $M/L$, the observed value of $\Omega$ is $010$ (CHDM) to $038$ (CDM)
24 citations
TL;DR: In this article, the zero point of the cluster-cluster correlation function is defined as a sensitive test for the shape of the power spectrum of initial fluctuations, and four independent measurements indicate that the 0 point should be in the range (40-60)$h^{-1}$Mpc.
Abstract: We propose the zero-point of the cluster-cluster correlation function as a sensitive test for the shape of the power spectrum of initial fluctuations. It is now possible to go beyond the power law description to measure the point at which the correlation function becomes zero. Four independent measurements indicate that the zero point, $r_0$, should be in the range (40-60)$h^{-1}$Mpc. The large value of $r_0$ at which the zero-point occurs rules out conventional CDM models independently of the assumed amplitude. Models with $\Omega 0.55$ are rejected. We present the results of numerical simulations of clusters in an $\Omega=1$ cosmological model with a mixture of cold plus hot dark matter (CHDM). The correlation function we determined for the simulated clusters has a zero-point, $r_0=55h^{-1}$Mpc that accurately matches the zero point of the observed function.