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تسجيل مستخدم جديدA Cosmic Void Catalog of SDSS DR12 BOSS Galaxies
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We present a cosmic void catalog using the large-scale structure galaxy catalog from the Baryon Oscillation Spectroscopic Survey (BOSS). This galaxy catalog is part of the Sloan Digital Sky Survey (SDSS) Data Release 12 and is the final catalog of SDSS-III. We take into account the survey boundaries, masks, and angular and radial selection functions, and apply the ZOBOV void finding algorithm to the galaxy catalog. We identify a total of 10,643 voids. After making quality cuts to ensure that the voids represent real underdense regions, we obtain 1,228 voids with effective radii spanning the range 20-100Mpc/h and with central densities that are, on average, 30% of the mean sample density. We relea
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We apply the Alcock-Paczynski (AP) test to the stacked voids identified using the large-scale structure galaxy catalog from the Baryon Oscillation Spectroscopic Survey (BOSS). This galaxy catalog is part of the Sloan Digital Sky Survey (SDSS) Data Re
lease 12 and is the final catalog of SDSS-III. We also use 1000 mock galaxy catalogs that match the geometry, density, and clustering properties of the BOSS sample in order to characterize the statistical uncertainties of our measurements and take into account systematic errors such as redshift space distortions. For both BOSS data and mock catalogs, we use the ZOBOV algorithm to identify voids, we stack together all voids with effective radii of 30-100Mpc/h in the redshift range 0.43-0.7, and we accurately measure the shape of the stacked voids. Our tests with the mock catalogs show that we measure the stacked void ellipticity with a statistical precision of 2.6%. We find that the stacked voids in redshift space are slightly squashed along the line of sight, which is consistent with previous studies. We repeat this measurement of stacked void shape in the BOSS data assuming several values of Omega_m within the flat LCDM model, and we compare to the mock catalogs in redshift space in order to perform the AP test. We obtain a constraint of $Omega_m = 0.38^{+0.18}_{-0.15}$ at the 68% confidence level from the AP test. We discuss the various sources of statistical and systematic noise that affect the constraining power of this method. In particular, we find that the measured ellipticity of stacked voids scales more weakly with cosmology than the standard AP prediction, leading to significantly weaker constraints. We discuss how AP constraints will improve in future surveys with larger volumes and densities.
In this study, we probe the transition to cosmic homogeneity in the Large Scale Structure (LSS) of the Universe using the CMASS galaxy sample of BOSS spectroscopic survey which covers the largest effective volume to date, $3 h^{-3} mathrm{Gpc}^3$ at
$0.43 leq z leq 0.7$. We study the scaled counts-in-spheres, $mathcal{N}(<r)$, and the fractal correlation dimension, $mathcal{D}_2(r)$, to assess the homogeneity scale of the universe using a $Landy & Szalay$ inspired estimator. Defining the scale of transition to homogeneity as the scale at which $mathcal{D}_2(r)$ reaches 3 within $1%$, i.e. $mathcal{D}_2(r)>2.97$ for $r>mathcal{R}_H$, we find $mathcal{R}_H = (63.3pm0.7) h^{-1} mathrm{Mpc}$, in agreement at the percentage level with the predictions of the $Lambda$CDM model $mathcal{R}_H=62.0 h^{-1} mathrm{Mpc}$. Thanks to the large cosmic depth of the survey, we investigate the redshift evolution of the transition to homogeneity scale and find agreement with the $Lambda$CDM prediction. Finally, we find that $mathcal{D}_2$ is compatible with $3$ at scales larger than $300 h^{-1} $Mpc in all redshift bins. These results consolidate the Cosmological Principle and represent a precise consistency test of the $Lambda CDM$ model.
We present the first high significance detection ($4.1sigma$) of the Baryon Acoustic Oscillations (BAO) feature in the galaxy bispectrum of the twelfth data release (DR12) of the Baryon Oscillation Spectroscopic Survey (BOSS) CMASS sample ($0.43 leq
z leq 0.7$). We measured the scale dilation parameter, $alpha$, using the power spectrum, bispectrum, and both simultaneously for DR12, plus 2048 MultiDark-PATCHY mocks in the North and South Galactic Caps (NGC and SGC, respectively), and the volume weighted averages of those two samples (N+SGC). The fitting to the mocks validated our analysis pipeline, yielding values consistent with the mock cosmology. By fitting to the power spectrum and bispectrum separately, we tested the robustness of our results, finding consistent values from the NGC, SGC and N+SGC in all cases. We found $D_{mathrm{V}} = 2032 pm 24 (mathrm{stat.}) pm 15 (mathrm{sys.})$ Mpc, $D_{mathrm{V}} = 2038 pm 55 (mathrm{stat.}) pm 15 (mathrm{sys.})$ Mpc, and $D_{mathrm{V}} = 2031 pm 22 (mathrm{stat.}) pm 10 (mathrm{sys.})$ Mpc from the N+SGC power spectrum, bispectrum and simultaneous fitting, respectively.
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actal correlation dimension, $D_2(r)$. For a homogeneous distribution $N(<! r) propto r^3$ and $D_2(r)=3$. Due to the uncertainty on tracer density evolution, 3D surveys can only probe homogeneity up to a redshift dependence, i.e. they probe so-called spatial isotropy. Our data demonstrate spatial isotropy of the quasar distribution in the redshift range $2.2<z<2.8$ in a model-independent way, independent of any FLRW fiducial cosmology, resulting in $3-langle D_2 rangle < 1.7 times 10^{-3}$ (2 $sigma$) over the range $250<r<1200 , h^{-1}$Mpc for the quasar distribution. If we assume that quasars do not have a bias much less than unity, this implies spatial isotropy of the matter distribution on large scales. Then, combining with the Copernican principle, we finally get homogeneity of the matter distribution on large scales. Alternatively, using a flat $Lambda$CDM fiducial cosmology with CMB-derived parameters, and measuring the quasar bias relative to this $Lambda$CDM model, our data provide a consistency check of the model, in terms of how homogeneous the Universe is on different scales. $D_2(r)$ is found to be compatible with our $Lambda$CDM model on the whole $10<r<1200 , h^{-1}$Mpc range. For the matter distribution we obtain $3-langle D_2 rangle < 5 times 10^{-5}$ (2 $sigma$) over the range $250<r<1200 , h^{-1}$Mpc, consistent with homogeneity on large scales.
[abridged] We present an anisotropic analysis of the baryonic acoustic oscillation (BAO) scale in the twelfth and final data release of the Baryonic Oscillation Spectroscopic Survey (BOSS). We independently analyse the LOWZ and CMASS galaxy samples:
the LOWZ sample contains contains 361 762 galaxies with an effective redshift of $z_{rm LOWZ}=0.32$; the CMASS sample consists of 777 202 galaxies with an effective redshift of $z_{rm CMASS}=0.57$. We extract the BAO peak position from the monopole power spectrum moment, $alpha_0$, and from the $mu^2$ moment, $alpha_2$, where $mu$ is the cosine of the angle to the line-of-sight. The $mu^2$-moment provides equivalent information to that available in the quadrupole but is simpler to analyse. After applying a reconstruction algorithm to reduce the BAO suppression by bulk motions, we measure the BAO peak position in the monopole and $mu^2$-moment, which are related to radial and angular shifts in scale. We report $H(z_{rm LOWZ})r_s(z_d)=(11.60pm0.60)cdot10^3 {rm km}s^{-1}$ and $D_A(z_{rm LOWZ})/r_s(z_d)=6.66pm0.16$ with a cross-correlation coefficient of $r_{HD_A}=0.41$, for the LOWZ sample; and $H(z_{rm CMASS})r_s(z_d)=(14.56pm0.37)cdot10^3 {rm km}s^{-1}$ and $D_A(z_{rm CMASS})/r_s(z_d)=9.42pm0.13$ with a cross-correlation coefficient of $r_{HD_A}=0.47$, for the CMASS sample. We combine these results with the measurements of the BAO peak position in the monopole and quadrupole correlation function of the same dataset citep[][companion paper]{Cuestaetal2015} and report the consensus values: $H(z_{rm LOWZ})r_s(z_d)=(11.63pm0.69)cdot10^3 {rm km}s^{-1}$ and $D_A(z_{rm LOWZ})/r_s(z_d)=6.67pm0.15$ with $r_{HD_A}=0.35$ for the LOWZ sample; $H(z_{rm CMASS})r_s(z_d)=(14.67pm0.42)cdot10^3 {rm km}s^{-1}$ and $D_A(z_{rm CMASS})/r_s(z_d)=9.47pm0.12$ with $r_{HD_A}=0.52$ for the CMASS sample.
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