We demonstrate the utility and constraining power of a new statistic for investigating galaxy bia... more We demonstrate the utility and constraining power of a new statistic for investigating galaxy bias: the galaxy-lensing phase difference. The statistic consists in taking the differences of the phases of the harmonic wave modes between the weak lensing convergence field and the galaxy count field. We use dark matter simulations populated with galaxies up to redshift z = 1 to test the performance of this estimator. We find that phase differences are sensitive to the absolute value of the second-order bias (c2 = b2/b1) and demonstrate why this is the case. For a $1500$ deg2 galaxy survey we recover c2 with an error of approximately 0.1 for a wide range of c2 values; current constraints from redshift surveys have errors of 0.1–0.6 depending on redshift. This new statistic is therefore expected to provide constraints for c2 which are complementary and competitive with constraining power by the conventional estimators from the power spectrum and bispectrum. For the Dark Energy Survey (DES...
We examine the density profiles of dark matter halos by analyzing data from the LasDamas (Large S... more We examine the density profiles of dark matter halos by analyzing data from the LasDamas (Large Suite of Dark Matter Simulations) project. LasDamas consists of a large suite of cosmological N-body simulations that follow the evolution of dark matter in the universe. The aim of LasDamas is to obtain adequate resolution in many large boxes, resulting in a huge volume appropriate for statistical studies of galaxies and halos. We measure density profiles for these halos, and fit NFW and other models to our measurements. With such a large dataset, we are able to study the full density profile distribution and its dependence on mass, redshift, and environment -- even in the regime of rare cluster-size halos. Finally, we investigate the sensitivity of our results to particle mass resolution, as well as choice of halo definition.
We present measurements of the anisotropic galaxy clustering from the Data Release 9 (DR9) CMASS ... more We present measurements of the anisotropic galaxy clustering from the Data Release 9 (DR9) CMASS sample of the SDSS-III Baryon Oscillation Spectroscopic Survey (BOSS). We analyze the broad-range shape of the monopole and quadrupole correlation functions to obtain constraints, at the effective redshift z=0.57 of the sample, on the Hubble expansion rate H(z), the angular-diameter distance D_A(z), the normalized growth rate f(z)\sigma_8(z), the physical matter density \Omega_m h^2, and the biased amplitude of matter fluctuation b\sigma_8(z). We obtain {H(0.57), D_A(0.57), f(0.57)\sigma_8(0.57), \Omega_m h^2, b\sigma_8(0.57)} = {87.6_{-6.8}^{+6.7}, 1396\pm73, 0.126_{-0.010}^{+0.008}, 1.19\pm0.14, 0.428\pm0.066} and their covariance matrix as well. The parameters which are not well constrained by our of galaxy clustering analysis are marginalized over with wide flat priors. Since no priors from other data sets (i.e., CMB) are adopted and no dark energy models are assumed, our results from BOSS CMASS galaxy clustering alone may be combined with other data sets, i.e. CMB, SNe, lensing or other galaxy clustering data to constrain the parameters of a given cosmological model. We show that the major power on constraining dark energy from the anisotropic galaxy clustering signal, as compared to the angular-averaged one (monopole), arises from including the normalized growth rate f(z)\sigma_8(z). In the case of the wCDM cosmological model our single-probe CMASS constraints, combined with CMB (WMAP9+SPT), yield a value for the dark energy equation of state parameter of w=-0.90\pm0.11. Therefore, it is important to include f(z)\sigma_8(z) while investigating the nature of dark energy with current and upcoming large-scale galaxy surveys.
We cross-correlate the third-year WMAP data with galaxy samples extracted from the SDSS DR5 (SDSS... more We cross-correlate the third-year WMAP data with galaxy samples extracted from the SDSS DR5 (SDSS5) covering 16% of the sky. These measurements confirm a positive cross-correlation, which is well fitted by the integrated Sachs-Wolfe (ISW) effect for flat LCDM models with a cosmological constant. The combined analysis of different samples gives Ω_Λ=0.79-0.83 (68% Confidence Level, CL) and Ω_Λ=0.75-0.85 (95% CL).
We use the joint measurement of geometry and growth from anisotropic galaxy clustering in the Bar... more We use the joint measurement of geometry and growth from anisotropic galaxy clustering in the Baryon Oscillation Spectroscopic Survey Data Release 9 CMASS sample reported by Reid et al. to constrain dark energy properties and possible deviations from the General Relativity. Assuming GR and taking a prior on the linear matter power spectrum at high redshift from the cosmic microwave background (CMB), anisotropic clustering of the CMASS DR9 galaxies alone constrains $\Omega_{\rm m} = 0.308 \pm 0.022$ and $100\Omega_{\rm k} = 5.9 \pm 4.8$ for $w = -1$, or $w = -0.91 \pm 0.12$ for $\Omega_k = 0$. When combined with the full CMB likelihood, the addition of the anisotropic clustering measurements to the spherically-averaged BAO location increases the constraining power on dark energy by a factor of 4 in a flat CDM cosmology with constant dark energy equation of state $w$ (giving $w = -0.87 \pm 0.05$). This impressive gain depends on our measurement of both the growth of structure and Alcock-Paczynski effect, and is not realised when marginalising over the amplitude of redshift space distortions. Combining with both the CMB and Supernovae Type Ia (SNeIa), we find $\Omega_{\rm m} = 0.281 \pm 0.014$ and $1000\Omega_{\rm k}=-9.2\pm5.0$ for $w = -1$, or $w_0 = -1.13 \pm 0.12$ and $w_{\rm a}=0.65 \pm 0.36$ assuming $\Omega_k = 0$. Finally, when a $\Lambda$CDM background expansion is assumed, the combination of our estimate of the growth rate with previous growth measurements provides tight constraints on the parameters describing possible deviations from GR giving $\gamma = 0.64 \pm 0.05$. For one parameter extensions of the flat $\Lambda$CDM model, we find a $\sim 2\sigma$ preference either for $w > -1$ or slower growth than in GR. However, the data is fully consistent with the concordance model, and the evidence for these additional parameters is weaker than $2\sigma$.
ABSTRACT Robust measurements based on current large-scale structure surveys require precise knowl... more ABSTRACT Robust measurements based on current large-scale structure surveys require precise knowledge of statistical and systematic errors. This can be obtained from large numbers of realistic mock galaxy catalogues that mimic the observed distribution of galaxies within the survey volume. To this end we present a fast, distributed-memory, planar-parallel code, L-PICOLA, which can be used to generate and evolve a set of initial conditions into a dark matter field much faster than a full non-linear N-Body simulation. Additionally, L-PICOLA has the ability to include primordial non-Gaussianity in the simulation and simulate the past lightcone at run-time, with optional replication of the simulation volume. Through comparisons to fully non-linear N-Body simulations we find that our code can reproduce the $z=0$ power spectrum and reduced bispectrum of dark matter to within 2% on all scales of interest to measurements of Baryon Acoustic Oscillations and Redshift Space Distortions, but 3 orders of magnitude faster. The accuracy, speed and scalability of this code, alongside the additional features we have implemented, make it extremely useful for both current and next generation large-scale structure surveys. L-PICOLA is publicly available at https://cullanhowlett.github.io/l-picola.
We study the abundance of clusters in the LasDamas suite of cosmological N-body simulations. Thes... more We study the abundance of clusters in the LasDamas suite of cosmological N-body simulations. These simulations contain an unprecedented volume (750 Gpc3/h3) and are seeded with initial conditions using second order lagrangian perturbation theory (2LPT) instead of the standard Zel'Dovich approximation (ZA). Recent results show that ZA leads to unphysical transients that predominantly inhibit the collapse of the earliest forming density peaks such as massive halos of galaxy clusters. We compare our results to simulations seeded with ZA, but using the same starting redshift, cosmology, simulation parameters, and phases. We find a significant systematic bias in the number density of clusters that grows with both halo mass and redshift. For masses greater than 2e14 Msun/h, we find that ZA underpredicts the abundance of halos by 3% at z=0 and 15% at z=1. For masses greater than 5e14 Msun/h, these rise to 5% and 20%, respectively. We show that this bias is only partially mitigated by u...
We measure RSD in the two-point correlation function of a sample of 63,163 spectroscopically iden... more We measure RSD in the two-point correlation function of a sample of 63,163 spectroscopically identified galaxies with $z < 0.2$, an epoch where there are currently only limited measurements, from the Sloan Digital Sky Survey (SDSS) Data Release 7 Main Galaxy Sample. Our sample, which we denote MGS, covers 6,813 deg$^2$ with an effective redshift $z_{eff}=0.15$ and is described in our companion paper (Paper I), which concentrates on BAO measurements. In order to validate the fitting methods used in both papers, and derive errors, we create and analyse 1000 mock catalogues using a new algorithm called PICOLA to generate accurate dark matter fields. Halos are then selected using a friends-of-friends algorithm, and populated with galaxies using a Halo-Occupation Distribution fitted to the data. We fit a model to the monopole and quadrupole moments of the MGS correlation function, including both the RSD and the Alcock-Paczynski effect, the latter of which results in anisotropic distor...
We create a sample of spectroscopically identified galaxies with $z < 0.2$ from the Sloan Digi... more We create a sample of spectroscopically identified galaxies with $z < 0.2$ from the Sloan Digital Sky Survey (SDSS) Data Release 7, covering 6813 deg$^2$. Galaxies are chosen to sample the highest mass haloes, with an effective bias of 1.5, allowing us to construct 1000 mock galaxy catalogs (described in Paper II), which we use to estimate statistical errors and test our methods. We use an estimate of the gravitational potential to "reconstruct" the linear density fluctuations, enhancing the Baryon Acoustic Oscillation (BAO) signal in the measured correlation function and power spectrum. Fitting to these measurements, we determine $D_{V}(z_{\rm eff}=0.15) = (664\pm25)(r_d/r_{d,{\rm fid}})$ Mpc; this is a better than 4 per cent distance measurement. This "fills the gap" in BAO distance ladder between previously measured local and higher redshift measurements, and affords significant improvement in constraining the properties of dark energy. Combining our measur...
ABSTRACT We present the cosmic distance scale as measured from the detection of the baryon acoust... more ABSTRACT We present the cosmic distance scale as measured from the detection of the baryon acoustic oscillations (BAO) in the clustering of galaxies from the SDSS-III Baryon Oscillation Spectroscopic Survey (BOSS). Our analysis of the Data Release 11 sample uses 1.15 million massive galaxies with spectroscopic redshifts spanning redshift 0.15 to 0.70 and covering 8500 square degrees. We find strong detections of the acoustic peak signature in two redshift bins centered at z=0.32 and z=0.57; in the upper redshift, the detection significance exceeds 8-sigma. These detections produce a robust measurement of the cosmic distance scale at these redshifts, including a 1% measurement of the distance to z=0.57. We discuss the cosmological implications of the measurements, including combinations with cosmic microwave background anisotropy data sets.
We cross-correlate the third-year WMAP data with galaxy samples extracted from the SDSS DR5 (SDSS... more We cross-correlate the third-year WMAP data with galaxy samples extracted from the SDSS DR5 (SDSS5) covering 16% of the sky. These measurements confirm a positive cross-correlation, which is well fitted by the integrated Sachs-Wolfe (ISW) effect for flat LCDM models with a cosmological constant. The combined analysis of different samples gives Omega_Lambda=0.79-0.83 (68% Confidence Level, CL) and Omega_Lambda=0.75-0.85 (95% CL).
We demonstrate the utility and constraining power of a new statistic for investigating galaxy bia... more We demonstrate the utility and constraining power of a new statistic for investigating galaxy bias: the galaxy-lensing phase difference. The statistic consists in taking the differences of the phases of the harmonic wave modes between the weak lensing convergence field and the galaxy count field. We use dark matter simulations populated with galaxies up to redshift z = 1 to test the performance of this estimator. We find that phase differences are sensitive to the absolute value of the second-order bias (c2 = b2/b1) and demonstrate why this is the case. For a $1500$ deg2 galaxy survey we recover c2 with an error of approximately 0.1 for a wide range of c2 values; current constraints from redshift surveys have errors of 0.1–0.6 depending on redshift. This new statistic is therefore expected to provide constraints for c2 which are complementary and competitive with constraining power by the conventional estimators from the power spectrum and bispectrum. For the Dark Energy Survey (DES...
We examine the density profiles of dark matter halos by analyzing data from the LasDamas (Large S... more We examine the density profiles of dark matter halos by analyzing data from the LasDamas (Large Suite of Dark Matter Simulations) project. LasDamas consists of a large suite of cosmological N-body simulations that follow the evolution of dark matter in the universe. The aim of LasDamas is to obtain adequate resolution in many large boxes, resulting in a huge volume appropriate for statistical studies of galaxies and halos. We measure density profiles for these halos, and fit NFW and other models to our measurements. With such a large dataset, we are able to study the full density profile distribution and its dependence on mass, redshift, and environment -- even in the regime of rare cluster-size halos. Finally, we investigate the sensitivity of our results to particle mass resolution, as well as choice of halo definition.
We present measurements of the anisotropic galaxy clustering from the Data Release 9 (DR9) CMASS ... more We present measurements of the anisotropic galaxy clustering from the Data Release 9 (DR9) CMASS sample of the SDSS-III Baryon Oscillation Spectroscopic Survey (BOSS). We analyze the broad-range shape of the monopole and quadrupole correlation functions to obtain constraints, at the effective redshift z=0.57 of the sample, on the Hubble expansion rate H(z), the angular-diameter distance D_A(z), the normalized growth rate f(z)\sigma_8(z), the physical matter density \Omega_m h^2, and the biased amplitude of matter fluctuation b\sigma_8(z). We obtain {H(0.57), D_A(0.57), f(0.57)\sigma_8(0.57), \Omega_m h^2, b\sigma_8(0.57)} = {87.6_{-6.8}^{+6.7}, 1396\pm73, 0.126_{-0.010}^{+0.008}, 1.19\pm0.14, 0.428\pm0.066} and their covariance matrix as well. The parameters which are not well constrained by our of galaxy clustering analysis are marginalized over with wide flat priors. Since no priors from other data sets (i.e., CMB) are adopted and no dark energy models are assumed, our results from BOSS CMASS galaxy clustering alone may be combined with other data sets, i.e. CMB, SNe, lensing or other galaxy clustering data to constrain the parameters of a given cosmological model. We show that the major power on constraining dark energy from the anisotropic galaxy clustering signal, as compared to the angular-averaged one (monopole), arises from including the normalized growth rate f(z)\sigma_8(z). In the case of the wCDM cosmological model our single-probe CMASS constraints, combined with CMB (WMAP9+SPT), yield a value for the dark energy equation of state parameter of w=-0.90\pm0.11. Therefore, it is important to include f(z)\sigma_8(z) while investigating the nature of dark energy with current and upcoming large-scale galaxy surveys.
We cross-correlate the third-year WMAP data with galaxy samples extracted from the SDSS DR5 (SDSS... more We cross-correlate the third-year WMAP data with galaxy samples extracted from the SDSS DR5 (SDSS5) covering 16% of the sky. These measurements confirm a positive cross-correlation, which is well fitted by the integrated Sachs-Wolfe (ISW) effect for flat LCDM models with a cosmological constant. The combined analysis of different samples gives Ω_Λ=0.79-0.83 (68% Confidence Level, CL) and Ω_Λ=0.75-0.85 (95% CL).
We use the joint measurement of geometry and growth from anisotropic galaxy clustering in the Bar... more We use the joint measurement of geometry and growth from anisotropic galaxy clustering in the Baryon Oscillation Spectroscopic Survey Data Release 9 CMASS sample reported by Reid et al. to constrain dark energy properties and possible deviations from the General Relativity. Assuming GR and taking a prior on the linear matter power spectrum at high redshift from the cosmic microwave background (CMB), anisotropic clustering of the CMASS DR9 galaxies alone constrains $\Omega_{\rm m} = 0.308 \pm 0.022$ and $100\Omega_{\rm k} = 5.9 \pm 4.8$ for $w = -1$, or $w = -0.91 \pm 0.12$ for $\Omega_k = 0$. When combined with the full CMB likelihood, the addition of the anisotropic clustering measurements to the spherically-averaged BAO location increases the constraining power on dark energy by a factor of 4 in a flat CDM cosmology with constant dark energy equation of state $w$ (giving $w = -0.87 \pm 0.05$). This impressive gain depends on our measurement of both the growth of structure and Alcock-Paczynski effect, and is not realised when marginalising over the amplitude of redshift space distortions. Combining with both the CMB and Supernovae Type Ia (SNeIa), we find $\Omega_{\rm m} = 0.281 \pm 0.014$ and $1000\Omega_{\rm k}=-9.2\pm5.0$ for $w = -1$, or $w_0 = -1.13 \pm 0.12$ and $w_{\rm a}=0.65 \pm 0.36$ assuming $\Omega_k = 0$. Finally, when a $\Lambda$CDM background expansion is assumed, the combination of our estimate of the growth rate with previous growth measurements provides tight constraints on the parameters describing possible deviations from GR giving $\gamma = 0.64 \pm 0.05$. For one parameter extensions of the flat $\Lambda$CDM model, we find a $\sim 2\sigma$ preference either for $w > -1$ or slower growth than in GR. However, the data is fully consistent with the concordance model, and the evidence for these additional parameters is weaker than $2\sigma$.
ABSTRACT Robust measurements based on current large-scale structure surveys require precise knowl... more ABSTRACT Robust measurements based on current large-scale structure surveys require precise knowledge of statistical and systematic errors. This can be obtained from large numbers of realistic mock galaxy catalogues that mimic the observed distribution of galaxies within the survey volume. To this end we present a fast, distributed-memory, planar-parallel code, L-PICOLA, which can be used to generate and evolve a set of initial conditions into a dark matter field much faster than a full non-linear N-Body simulation. Additionally, L-PICOLA has the ability to include primordial non-Gaussianity in the simulation and simulate the past lightcone at run-time, with optional replication of the simulation volume. Through comparisons to fully non-linear N-Body simulations we find that our code can reproduce the $z=0$ power spectrum and reduced bispectrum of dark matter to within 2% on all scales of interest to measurements of Baryon Acoustic Oscillations and Redshift Space Distortions, but 3 orders of magnitude faster. The accuracy, speed and scalability of this code, alongside the additional features we have implemented, make it extremely useful for both current and next generation large-scale structure surveys. L-PICOLA is publicly available at https://cullanhowlett.github.io/l-picola.
We study the abundance of clusters in the LasDamas suite of cosmological N-body simulations. Thes... more We study the abundance of clusters in the LasDamas suite of cosmological N-body simulations. These simulations contain an unprecedented volume (750 Gpc3/h3) and are seeded with initial conditions using second order lagrangian perturbation theory (2LPT) instead of the standard Zel'Dovich approximation (ZA). Recent results show that ZA leads to unphysical transients that predominantly inhibit the collapse of the earliest forming density peaks such as massive halos of galaxy clusters. We compare our results to simulations seeded with ZA, but using the same starting redshift, cosmology, simulation parameters, and phases. We find a significant systematic bias in the number density of clusters that grows with both halo mass and redshift. For masses greater than 2e14 Msun/h, we find that ZA underpredicts the abundance of halos by 3% at z=0 and 15% at z=1. For masses greater than 5e14 Msun/h, these rise to 5% and 20%, respectively. We show that this bias is only partially mitigated by u...
We measure RSD in the two-point correlation function of a sample of 63,163 spectroscopically iden... more We measure RSD in the two-point correlation function of a sample of 63,163 spectroscopically identified galaxies with $z < 0.2$, an epoch where there are currently only limited measurements, from the Sloan Digital Sky Survey (SDSS) Data Release 7 Main Galaxy Sample. Our sample, which we denote MGS, covers 6,813 deg$^2$ with an effective redshift $z_{eff}=0.15$ and is described in our companion paper (Paper I), which concentrates on BAO measurements. In order to validate the fitting methods used in both papers, and derive errors, we create and analyse 1000 mock catalogues using a new algorithm called PICOLA to generate accurate dark matter fields. Halos are then selected using a friends-of-friends algorithm, and populated with galaxies using a Halo-Occupation Distribution fitted to the data. We fit a model to the monopole and quadrupole moments of the MGS correlation function, including both the RSD and the Alcock-Paczynski effect, the latter of which results in anisotropic distor...
We create a sample of spectroscopically identified galaxies with $z < 0.2$ from the Sloan Digi... more We create a sample of spectroscopically identified galaxies with $z < 0.2$ from the Sloan Digital Sky Survey (SDSS) Data Release 7, covering 6813 deg$^2$. Galaxies are chosen to sample the highest mass haloes, with an effective bias of 1.5, allowing us to construct 1000 mock galaxy catalogs (described in Paper II), which we use to estimate statistical errors and test our methods. We use an estimate of the gravitational potential to "reconstruct" the linear density fluctuations, enhancing the Baryon Acoustic Oscillation (BAO) signal in the measured correlation function and power spectrum. Fitting to these measurements, we determine $D_{V}(z_{\rm eff}=0.15) = (664\pm25)(r_d/r_{d,{\rm fid}})$ Mpc; this is a better than 4 per cent distance measurement. This "fills the gap" in BAO distance ladder between previously measured local and higher redshift measurements, and affords significant improvement in constraining the properties of dark energy. Combining our measur...
ABSTRACT We present the cosmic distance scale as measured from the detection of the baryon acoust... more ABSTRACT We present the cosmic distance scale as measured from the detection of the baryon acoustic oscillations (BAO) in the clustering of galaxies from the SDSS-III Baryon Oscillation Spectroscopic Survey (BOSS). Our analysis of the Data Release 11 sample uses 1.15 million massive galaxies with spectroscopic redshifts spanning redshift 0.15 to 0.70 and covering 8500 square degrees. We find strong detections of the acoustic peak signature in two redshift bins centered at z=0.32 and z=0.57; in the upper redshift, the detection significance exceeds 8-sigma. These detections produce a robust measurement of the cosmic distance scale at these redshifts, including a 1% measurement of the distance to z=0.57. We discuss the cosmological implications of the measurements, including combinations with cosmic microwave background anisotropy data sets.
We cross-correlate the third-year WMAP data with galaxy samples extracted from the SDSS DR5 (SDSS... more We cross-correlate the third-year WMAP data with galaxy samples extracted from the SDSS DR5 (SDSS5) covering 16% of the sky. These measurements confirm a positive cross-correlation, which is well fitted by the integrated Sachs-Wolfe (ISW) effect for flat LCDM models with a cosmological constant. The combined analysis of different samples gives Omega_Lambda=0.79-0.83 (68% Confidence Level, CL) and Omega_Lambda=0.75-0.85 (95% CL).
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