By semi analytic approach, the estimate of the properties of the largest virialized dark halos in the present universe is presented for three different scenarios of structure formation: SCDM, ΛCDM and OCDM models. Th...By semi analytic approach, the estimate of the properties of the largest virialized dark halos in the present universe is presented for three different scenarios of structure formation: SCDM, ΛCDM and OCDM models. The resulting virial mass increases from the lowest values of 1.6×10 15 h -1 M ⊙ in OCDM, the mid range values of 9.0×10 15 h -1 M ⊙ in ΛCDM, to the highest values of 20.9×10 15 h -1 M ⊙ in SCDM. As compared with the largest virialized object seen in the universe, the OCDM model can safely be ruled out. Therefore, the computation in this paper favors the prevailing ΛCDM model in which superclusters may be marginally regarded as dynamically virialized systems.展开更多
The early universe inflation is well known as a promising theory to explain the origin of large-scale structure of universe and to solve the early universe pressing problems. For a reasonable inflation model, the pote...The early universe inflation is well known as a promising theory to explain the origin of large-scale structure of universe and to solve the early universe pressing problems. For a reasonable inflation model, the potential during inflation must be very flat, at least, in the direction of the inflaton. To construct the inflaton potential all the known related astrophysics observations should be included. For a general tree-level hybrid inflation potential, which is notdiscussed fully so far, the parameters in it are shown how to be constrained via the astrophysics data observed and to be obtained to the expected accuracy, and to be consistent with cosmology requirements.展开更多
We explore features of redshift distortion in Fourier analysis of N-body simulations. The phases of the Fourier modes of dark matter density fluctuation are generally shifted by the peculiar motion along the line of s...We explore features of redshift distortion in Fourier analysis of N-body simulations. The phases of the Fourier modes of dark matter density fluctuation are generally shifted by the peculiar motion along the line of sight, the induced phase shift is stochastic and has a probability distribution function （PDF） that is symmetric about the peak at zero shift and whose exact shape depends on the wave vector, except on very large scales where phases are invariant by linear perturbation theory. Analysis of the phase shifts motivates our phenomenological models for the bispectrum in redshift space. Comparison with simulations shows that our toy models are very successful in modeling bispectrum of equilateral and isosceles trian- gles at large scales. In the second part we compare the monopole of the power spectrum and bispectrum in the radial and plane-parallel distortion to test the plane-parallel approximation. We confirm the results of Scoccimarro that difference of power spectrum is at the level of 10%, and, in the reduced bispectrum, the difference is as small as a few percent. However, on the plane perpendicular to the line of sight of kz = 0, the difference in power spectrum be- tween the radial and plane-parallel approximation can be more than - 10%, and even worse on very small scales. Such difference is prominent for bispectrum, especially for configura- tions of tilted triangles. Non-Ganssian signals under the radial distortion on small scales are systematically biased downside than are in the plane-parallel approximation, with amplitudes depending on the opening angle of the sample point to the observer. This observation gives warning to the practice of using the power spectrum and bispectrum measured on the kz = 0 plane as estimates of the real space statistics.展开更多
We have accurately evaluated the halo pairwise velocity dispersion and the halo mean streaming velocity in the LCDM model (the fiat ω0 = 0.3 model) using a set of high-resolution N-body simulations. Based on the simu...We have accurately evaluated the halo pairwise velocity dispersion and the halo mean streaming velocity in the LCDM model (the fiat ω0 = 0.3 model) using a set of high-resolution N-body simulations. Based on the simulation results, we have developed a model for the pairwise velocity dispersion of halos. Our model agrees with the simulation results over all scales we studied. We have also tested the model of Sheth et al. for the mean streaming motion of halos derived from the pair-conservation equation. We found that their model reproduces the simulation data very well on large scale, but under-predicts the streaming motion on scales r < 10 h-1 Mpc. We have introduced an empirical relation to improve their model. These improved models are useful for predicting the redshift correlation functions and the redshift power spectrum of galaxies if the halo occupation number model, e.g. the cluster weighted model, is given for the galaxies.展开更多
文摘By semi analytic approach, the estimate of the properties of the largest virialized dark halos in the present universe is presented for three different scenarios of structure formation: SCDM, ΛCDM and OCDM models. The resulting virial mass increases from the lowest values of 1.6×10 15 h -1 M ⊙ in OCDM, the mid range values of 9.0×10 15 h -1 M ⊙ in ΛCDM, to the highest values of 20.9×10 15 h -1 M ⊙ in SCDM. As compared with the largest virialized object seen in the universe, the OCDM model can safely be ruled out. Therefore, the computation in this paper favors the prevailing ΛCDM model in which superclusters may be marginally regarded as dynamically virialized systems.
基金the One Hundred Talents projectShanghai Pujiang Program(07pj14102)+2 种基金973 Program(2007CB815402)the CAS Knowledge Innovation Program(KJCX2-YW-T05)grants from NSFC(10533030,10673023)
文摘The early universe inflation is well known as a promising theory to explain the origin of large-scale structure of universe and to solve the early universe pressing problems. For a reasonable inflation model, the potential during inflation must be very flat, at least, in the direction of the inflaton. To construct the inflaton potential all the known related astrophysics observations should be included. For a general tree-level hybrid inflation potential, which is notdiscussed fully so far, the parameters in it are shown how to be constrained via the astrophysics data observed and to be obtained to the expected accuracy, and to be consistent with cosmology requirements.
基金Supported by the National Natural Science Foundation of China.
文摘We explore features of redshift distortion in Fourier analysis of N-body simulations. The phases of the Fourier modes of dark matter density fluctuation are generally shifted by the peculiar motion along the line of sight, the induced phase shift is stochastic and has a probability distribution function （PDF） that is symmetric about the peak at zero shift and whose exact shape depends on the wave vector, except on very large scales where phases are invariant by linear perturbation theory. Analysis of the phase shifts motivates our phenomenological models for the bispectrum in redshift space. Comparison with simulations shows that our toy models are very successful in modeling bispectrum of equilateral and isosceles trian- gles at large scales. In the second part we compare the monopole of the power spectrum and bispectrum in the radial and plane-parallel distortion to test the plane-parallel approximation. We confirm the results of Scoccimarro that difference of power spectrum is at the level of 10%, and, in the reduced bispectrum, the difference is as small as a few percent. However, on the plane perpendicular to the line of sight of kz = 0, the difference in power spectrum be- tween the radial and plane-parallel approximation can be more than - 10%, and even worse on very small scales. Such difference is prominent for bispectrum, especially for configura- tions of tilted triangles. Non-Ganssian signals under the radial distortion on small scales are systematically biased downside than are in the plane-parallel approximation, with amplitudes depending on the opening angle of the sample point to the observer. This observation gives warning to the practice of using the power spectrum and bispectrum measured on the kz = 0 plane as estimates of the real space statistics.
基金the National Natural Science Foundation of China.
文摘We have accurately evaluated the halo pairwise velocity dispersion and the halo mean streaming velocity in the LCDM model (the fiat ω0 = 0.3 model) using a set of high-resolution N-body simulations. Based on the simulation results, we have developed a model for the pairwise velocity dispersion of halos. Our model agrees with the simulation results over all scales we studied. We have also tested the model of Sheth et al. for the mean streaming motion of halos derived from the pair-conservation equation. We found that their model reproduces the simulation data very well on large scale, but under-predicts the streaming motion on scales r < 10 h-1 Mpc. We have introduced an empirical relation to improve their model. These improved models are useful for predicting the redshift correlation functions and the redshift power spectrum of galaxies if the halo occupation number model, e.g. the cluster weighted model, is given for the galaxies.
