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HORIZON RUN 3: TOPOLOGY AS A STANDARD RULER
Speare, Robert,Gott, J. Richard,Kim, Juhan,Park, Changbom IOP Publishing 2015 The Astrophysical journal Vol.799 No.2
<P>We study the physically self-bound cold dark matter halo distribution, which we associate with the massive galaxies within Horizon Run 3, to estimate the accuracy of the determination of the cosmological distance scale measured by the topology analysis. We apply the routine 'Contour 3D' to the 108 Mock Survey of p steradians out to redshift z = 0.6, which effectively corresponds to the SDSS-III Baryon Oscillation Spectroscopic Survey (BOSS) survey, and compare the topology with that of a Gaussian random phase field. We find that given three separate smoothing lengths. = 15, 21, and 34 h(-1) Mpc, the least chi(2) fit genus per unit volume (g) yields a 1.7% fractional uncertainty in smoothing length and angular diameter distance to z = 0.6. This is an improvement on former calibrations and presents an error estimate competitive with baryon acoustic oscillation scale techniques. We also present three-dimensional graphics of the Horizon Run 3 spherical mock survey to show a wealth of large-scale structures of the universe that are expected for surveys like BOSS.</P>
THE CHALLENGE OF THE LARGEST STRUCTURES IN THE UNIVERSE TO COSMOLOGY
Park, Changbom,Choi, Yun-Young,Kim, Juhan,Gott III, J. Richard,Kim, Sungsoo S.,Kim, Kap-Sung IOP Publishing 2012 ASTROPHYSICAL JOURNAL LETTERS - Vol.759 No.1
<P>Large galaxy redshift surveys have long been used to constrain cosmological models and structure formation scenarios. In particular, the largest structures discovered observationally are thought to carry critical information on the amplitude of large-scale density fluctuations or homogeneity of the universe, and have often challenged the standard cosmological framework. The Sloan Great Wall (SGW) recently found in the Sloan Digital Sky Survey (SDSS) region casts doubt on the concordance cosmological model with a cosmological constant (i.e., the flat Lambda CDM model). Here we show that the existence of the SGW is perfectly consistent with the Lambda CDM model, a result that only our very large cosmological N-body simulation (the Horizon Run 2, HR2) could supply. In addition, we report on the discovery of a void complex in the SDSS much larger than the SGW, and show that such size of the largest void is also predicted in the Lambda CDM paradigm. Our results demonstrate that an initially homogeneous isotropic universe with primordial Gaussian random phase density fluctuations growing in accordance with the general relativity can explain the richness and size of the observed large-scale structures in the SDSS. Using the HR2 simulation we predict that a future galaxy redshift survey about four times deeper or with 3mag fainter limit than the SDSS should reveal a largest structure of bright galaxies about twice as big as the SGW.</P>
A TOPOLOGICAL ANALYSIS OF LARGE-SCALE STRUCTURE, STUDIED USING THE CMASS SAMPLE OF SDSS-III
Parihar, Prachi,Vogeley, Michael S.,Gott III, J. Richard,Choi, Yun-Young,Kim, Juhan,Kim, Sungsoo S.,Speare, Robert,Brownstein, Joel R.,Brinkmann, J. IOP Publishing 2014 The Astrophysical journal Vol.796 No.2
<P>We study the three-dimensional genus topology of large-scale structure using the northern region of the CMASS Data Release 10 (DR10) sample of the SDSS-III Baryon Oscillation Spectroscopic Survey. We select galaxies with redshift 0.452 < z < 0.625 and with a stellar mass M-stellar > 10(11.56) M-circle dot. We study the topology at two smoothing lengths: R-G = 21 h(-1) Mpc and R-G = 34 h(-1) Mpc. The genus topology studied at the R-G = 21 h(-1) Mpc scale results in the highest genus amplitude observed to date. The CMASS sample yields a genus curve that is characteristic of one produced by Gaussian random phase initial conditions. The data thus support the standard model of inflation where random quantum fluctuations in the early universe produced Gaussian random phase initial conditions. Modest deviations in the observed genus from random phase are as expected from shot noise effects and the nonlinear evolution of structure. We suggest the use of a fitting formula motivated by perturbation theory to characterize the shift and asymmetries in the observed genus curve with a single parameter. We construct 54 mock SDSS CMASS surveys along the past light cone from the Horizon Run 3 (HR3) N-body simulations, where gravitationally bound dark matter subhalos are identified as the sites of galaxy formation. We study the genus topology of the HR3 mock surveys with the same geometry and sampling density as the observational sample and find the observed genus topology to be consistent with ACDM as simulated by the HR3 mock samples. We conclude that the topology of the large-scale structure in the SDSS CMASS sample is consistent with cosmological models having primordial Gaussian density fluctuations growing in accordance with general relativity to form galaxies in massive dark matter halos.</P>