The Experts below are selected from a list of 23136 Experts worldwide ranked by ideXlab platform
Steven W. Allen - One of the best experts on this subject based on the ideXlab platform.
-
New constraints on f(R) gravity from clusters of galaxies
Physical Review D, 2015Co-Authors: Matteo Cataneo, Adam Mantz, Steven W. Allen, David Rapetti, Patrick L. Kelly, Fabian Schmidt, Douglas Applegate, Anja Von Der Linden, R. Glenn MorrisAbstract:The abundance of massive galaxy clusters is a powerful probe of departures from general relativity (GR) on cosmic scales. Despite current stringent constraints placed by stellar and galactic tests, on larger scales alternative theories of gravity such as $f(R)$ can still work as effective theories. Here we present constraints on two popular models of $f(R)$, Hu-Sawicki and ``designer,'' derived from a fully self-consistent analysis of current samples of x-ray selected clusters and accounting for all the covariances between cosmological and astrophysical parameters. Using cluster number counts in combination with recent data from the cosmic microwave background (CMB) and the CMB lensing potential generated by large scale structures, as well as with other cosmological constraints on the background expansion history and its Mean Matter Density, we obtain the upper bounds ${\mathrm{log}}_{10}|{f}_{R0}|l4.79$ and ${\mathrm{log}}_{10}{B}_{0}l3.75$ at the 95.4% confidence level, for the Hu-Sawicki (with $n=1$) and designer models, respectively. The robustness of our results derives from high-quality cluster growth data for the most massive clusters known out to redshifts $z\ensuremath{\sim}0.5$, a tight control of systematic uncertainties including an accurate and precise mass calibration from weak gravitational lensing data, and the use of the full shape of the halo mass function over the mass range of our data.
-
Weighing the giants – IV. Cosmology and neutrino mass
Monthly Notices of the Royal Astronomical Society, 2014Co-Authors: Adam Mantz, Steven W. Allen, David Rapetti, Patrick L. Kelly, Robert Schmidt, Douglas Applegate, Anja Von Der Linden, R. Glenn Morris, Saroj Adhikari, Mark T. AllenAbstract:We employ robust weak gravitational lensing measurements to improve cosmological constraints from measurements of the galaxy cluster mass function and its evolution, using X-ray selected clusters detected in the ROSAT All-Sky Survey. Our lensing analysis constrains the absolute mass scale of such clusters at the 8 per cent level, including both statistical and systematic uncertainties. Combining it with the survey data and X-ray follow-up observations, we find a tight constraint on a combination of the Mean Matter Density and late-time normalization of the Matter power spectrum, $\sigma_8(\Omega_m/0.3)^{0.17}=0.81\pm0.03$, with marginalized, one-dimensional constraints of $\Omega_m=0.26\pm0.03$ and $\sigma_8=0.83\pm0.04$. For these two parameters, this represents a factor of two improvement in precision with respect to previous work, primarily due to the reduced systematic uncertainty in the absolute mass calibration provided by the lensing analysis. Our new results are in good agreement with constraints from cosmic microwave background (CMB) data, both WMAP and Planck (plus WMAP polarization), under the assumption of a flat $\Lambda$CDM cosmology with minimal neutrino mass. Consequently, we find no evidence for non-minimal neutrino mass from the combination of cluster data with CMB, supernova and baryon acoustic oscillation measurements, regardless of which all-sky CMB data set is used (and independent of the recent claimed detection of B-modes on degree scales). We also present improved constraints on models of dark energy (both constant and evolving), modifications of gravity, and primordial non-Gaussianity. Assuming flatness, the constraints for a constant dark energy equation of state from the cluster data alone are at the 15 per cent level, improving to $\sim 6$ per cent when the cluster data are combined with other leading probes.
-
Measuring cosmic distances with galaxy clusters
arXiv: Cosmology and Nongalactic Astrophysics, 2013Co-Authors: Steven W. Allen, D. Rapetti, A. Von Der Linden, Patrick L. Kelly, D. E. Applegate, A. Mantz, Robert Schmidt, R. G. MorrisAbstract:In addition to cosmological tests based on the mass function and clustering of galaxy clusters, which probe the growth of cosmic structure, nature offers two independent ways of using clusters to measure cosmic distances. The first uses measurements of the X-ray emitting gas mass fraction, which is an approximately standard quantity, independent of mass and redshift, for the most massive clusters. The second uses combined millimeter (mm) and X-ray measurements of cluster pressure profiles. We review these methods, their current status and the prospects for improvements over the next decade. For the first technique, which currently provides comparable dark energy constraints to type Ia supernova studies, improvements of a factor of 6 or more should be readily achievable, together with tight constraints on the Mean Matter Density that are largely independent of the cosmological model assumed. Realizing this potential will require a coordinated, multiwavelength approach, utilizing new cluster surveys, X-ray, optical and mm facilities, and a continued emphasis on improved hydrodynamical simulations.
-
A combined measurement of cosmic growth and expansion from clusters of galaxies, the CMB and galaxy clustering
Monthly Notices of the Royal Astronomical Society, 2013Co-Authors: David Rapetti, Adam Mantz, Steven W. Allen, Chris Blake, David Parkinson, Florian BeutlerAbstract:Combining galaxy cluster data from the ROSAT All-Sky Survey and the Chandra Xray Observatory, cosmic microwave background data from the Wilkinson Microwave Anisotropy Probe, and galaxy clustering data from the WiggleZ Dark Energy Survey, the 6-degree Field Galaxy Survey and the Sloan Digital Sky Survey III, we test for consistency the cosmic growth of structure predicted by General Relativity (GR) and the cosmic expansion history predicted by the cosmological constant plus cold dark Matter paradigm (�CDM). The combination of these three independent, well studied measurements of the evolution of the Mean energy Density and its fluctuations is able to break strong degeneracies between model parameters. We model the key properties of cosmic growth with the normalization of the Matter power spectrum, σ8, and the cosmic growth index, γ, and those of cosmic expansion with the Mean Matter Density, m, the Hubble constant, H0, and a kinematical parameter equivalent to that for the dark energy equation of state, w. For a spatially flat geometry, w = −1, and allowing for systematic uncertainties, we obtain σ8 = 0.785± 0.019 and γ = 0.570 +0.064 0.063 (at the 68.3 per cent confidence level). Allowing both w and γ to vary we find w = −0.950 +0.069 0.070 and γ = 0.533 ± 0.080. To further tighten the constraints on the expansion parameters, we also include supernova, Cepheid variable and baryon acoustic oscillation data. For w = −1, we have γ = 0.616±0.061. For our most general model with a free w, we measure m = 0.278 +0.012 0.011 , H0 = 70.0 ± 1.3 km s 1 Mpc 1 and w = −0.987 +0.054 0.053 for the expansion parameters, and σ8 = 0.789 ± 0.019 and γ = 0.604±0.078 for the growth parameters. These results are in excellent agreement with GR+�CDM (γ ≃ 0.55; w = −1) and represent the tightest and most robust simultaneous constraint on cosmic growth and expansion to date.
-
Constraints on modified gravity from the observed X-ray luminosity function of galaxy clusters
Monthly Notices of the Royal Astronomical Society, 2009Co-Authors: David Rapetti, Adam Mantz, Steven W. Allen, Harald EbelingAbstract:We use measurements of the growth of cosmic structure, as inferred from the observed evolution of the X-ray luminosity function (XLF) of galaxy clusters, to constrain departures from General Relativity (GR) on cosmological scales. We employ the popular growth rate parameterization, Omega_m(z)^gamma, for which GR predicts a growth index gamma~0.55. We use observations of the cosmic microwave background (CMB), type Ia supernovae (SNIa), and X-ray cluster gas-mass fractions (fgas), to simultaneously constrain the expansion history and energy content of the Universe, as described by the background model parameters: Omega_m, w, and Omega_k, i.e., the Mean Matter Density, the dark energy equation of state parameter, and the Mean curvature, respectively. Using conservative allowances for systematic uncertainties, in particular for the evolution of the mass-luminosity scaling relation in the XLF analysis, we find gamma=0.51+0.16-0.15 and Omega_m=0.27+-0.02 (68.3 per cent confidence limits), for a flat cosmological constant (LCDM) background model. Allowing w to be a free parameter, we find gamma=0.44+0.17-0.15. Relaxing the flatness prior in the LCDM model, we obtain gamma=0.51+0.19-0.16. When in addition to the XLF data we use the CMB data to constrain gamma through the ISW effect, we obtain a combined constraint of gamma=0.45+0.14-0.12 for the flat LCDM model. Our analysis provides the tightest constraints to date on the growth index. We find no evidence for departures from General Relativity on cosmological scales.
David Rapetti - One of the best experts on this subject based on the ideXlab platform.
-
New constraints on f(R) gravity from clusters of galaxies
Physical Review D, 2015Co-Authors: Matteo Cataneo, Adam Mantz, Steven W. Allen, David Rapetti, Patrick L. Kelly, Fabian Schmidt, Douglas Applegate, Anja Von Der Linden, R. Glenn MorrisAbstract:The abundance of massive galaxy clusters is a powerful probe of departures from general relativity (GR) on cosmic scales. Despite current stringent constraints placed by stellar and galactic tests, on larger scales alternative theories of gravity such as $f(R)$ can still work as effective theories. Here we present constraints on two popular models of $f(R)$, Hu-Sawicki and ``designer,'' derived from a fully self-consistent analysis of current samples of x-ray selected clusters and accounting for all the covariances between cosmological and astrophysical parameters. Using cluster number counts in combination with recent data from the cosmic microwave background (CMB) and the CMB lensing potential generated by large scale structures, as well as with other cosmological constraints on the background expansion history and its Mean Matter Density, we obtain the upper bounds ${\mathrm{log}}_{10}|{f}_{R0}|l4.79$ and ${\mathrm{log}}_{10}{B}_{0}l3.75$ at the 95.4% confidence level, for the Hu-Sawicki (with $n=1$) and designer models, respectively. The robustness of our results derives from high-quality cluster growth data for the most massive clusters known out to redshifts $z\ensuremath{\sim}0.5$, a tight control of systematic uncertainties including an accurate and precise mass calibration from weak gravitational lensing data, and the use of the full shape of the halo mass function over the mass range of our data.
-
Weighing the giants – IV. Cosmology and neutrino mass
Monthly Notices of the Royal Astronomical Society, 2014Co-Authors: Adam Mantz, Steven W. Allen, David Rapetti, Patrick L. Kelly, Robert Schmidt, Douglas Applegate, Anja Von Der Linden, R. Glenn Morris, Saroj Adhikari, Mark T. AllenAbstract:We employ robust weak gravitational lensing measurements to improve cosmological constraints from measurements of the galaxy cluster mass function and its evolution, using X-ray selected clusters detected in the ROSAT All-Sky Survey. Our lensing analysis constrains the absolute mass scale of such clusters at the 8 per cent level, including both statistical and systematic uncertainties. Combining it with the survey data and X-ray follow-up observations, we find a tight constraint on a combination of the Mean Matter Density and late-time normalization of the Matter power spectrum, $\sigma_8(\Omega_m/0.3)^{0.17}=0.81\pm0.03$, with marginalized, one-dimensional constraints of $\Omega_m=0.26\pm0.03$ and $\sigma_8=0.83\pm0.04$. For these two parameters, this represents a factor of two improvement in precision with respect to previous work, primarily due to the reduced systematic uncertainty in the absolute mass calibration provided by the lensing analysis. Our new results are in good agreement with constraints from cosmic microwave background (CMB) data, both WMAP and Planck (plus WMAP polarization), under the assumption of a flat $\Lambda$CDM cosmology with minimal neutrino mass. Consequently, we find no evidence for non-minimal neutrino mass from the combination of cluster data with CMB, supernova and baryon acoustic oscillation measurements, regardless of which all-sky CMB data set is used (and independent of the recent claimed detection of B-modes on degree scales). We also present improved constraints on models of dark energy (both constant and evolving), modifications of gravity, and primordial non-Gaussianity. Assuming flatness, the constraints for a constant dark energy equation of state from the cluster data alone are at the 15 per cent level, improving to $\sim 6$ per cent when the cluster data are combined with other leading probes.
-
A combined measurement of cosmic growth and expansion from clusters of galaxies, the CMB and galaxy clustering
Monthly Notices of the Royal Astronomical Society, 2013Co-Authors: David Rapetti, Adam Mantz, Steven W. Allen, Chris Blake, David Parkinson, Florian BeutlerAbstract:Combining galaxy cluster data from the ROSAT All-Sky Survey and the Chandra Xray Observatory, cosmic microwave background data from the Wilkinson Microwave Anisotropy Probe, and galaxy clustering data from the WiggleZ Dark Energy Survey, the 6-degree Field Galaxy Survey and the Sloan Digital Sky Survey III, we test for consistency the cosmic growth of structure predicted by General Relativity (GR) and the cosmic expansion history predicted by the cosmological constant plus cold dark Matter paradigm (�CDM). The combination of these three independent, well studied measurements of the evolution of the Mean energy Density and its fluctuations is able to break strong degeneracies between model parameters. We model the key properties of cosmic growth with the normalization of the Matter power spectrum, σ8, and the cosmic growth index, γ, and those of cosmic expansion with the Mean Matter Density, m, the Hubble constant, H0, and a kinematical parameter equivalent to that for the dark energy equation of state, w. For a spatially flat geometry, w = −1, and allowing for systematic uncertainties, we obtain σ8 = 0.785± 0.019 and γ = 0.570 +0.064 0.063 (at the 68.3 per cent confidence level). Allowing both w and γ to vary we find w = −0.950 +0.069 0.070 and γ = 0.533 ± 0.080. To further tighten the constraints on the expansion parameters, we also include supernova, Cepheid variable and baryon acoustic oscillation data. For w = −1, we have γ = 0.616±0.061. For our most general model with a free w, we measure m = 0.278 +0.012 0.011 , H0 = 70.0 ± 1.3 km s 1 Mpc 1 and w = −0.987 +0.054 0.053 for the expansion parameters, and σ8 = 0.789 ± 0.019 and γ = 0.604±0.078 for the growth parameters. These results are in excellent agreement with GR+�CDM (γ ≃ 0.55; w = −1) and represent the tightest and most robust simultaneous constraint on cosmic growth and expansion to date.
-
Constraints on modified gravity from the observed X-ray luminosity function of galaxy clusters
Monthly Notices of the Royal Astronomical Society, 2009Co-Authors: David Rapetti, Adam Mantz, Steven W. Allen, Harald EbelingAbstract:We use measurements of the growth of cosmic structure, as inferred from the observed evolution of the X-ray luminosity function (XLF) of galaxy clusters, to constrain departures from General Relativity (GR) on cosmological scales. We employ the popular growth rate parameterization, Omega_m(z)^gamma, for which GR predicts a growth index gamma~0.55. We use observations of the cosmic microwave background (CMB), type Ia supernovae (SNIa), and X-ray cluster gas-mass fractions (fgas), to simultaneously constrain the expansion history and energy content of the Universe, as described by the background model parameters: Omega_m, w, and Omega_k, i.e., the Mean Matter Density, the dark energy equation of state parameter, and the Mean curvature, respectively. Using conservative allowances for systematic uncertainties, in particular for the evolution of the mass-luminosity scaling relation in the XLF analysis, we find gamma=0.51+0.16-0.15 and Omega_m=0.27+-0.02 (68.3 per cent confidence limits), for a flat cosmological constant (LCDM) background model. Allowing w to be a free parameter, we find gamma=0.44+0.17-0.15. Relaxing the flatness prior in the LCDM model, we obtain gamma=0.51+0.19-0.16. When in addition to the XLF data we use the CMB data to constrain gamma through the ISW effect, we obtain a combined constraint of gamma=0.45+0.14-0.12 for the flat LCDM model. Our analysis provides the tightest constraints to date on the growth index. We find no evidence for departures from General Relativity on cosmological scales.
-
New constraints on dark energy from the observed growth of the most X-ray luminous galaxy clusters
Monthly Notices of the Royal Astronomical Society, 2008Co-Authors: Adam Mantz, Steven W. Allen, Harald Ebeling, David RapettiAbstract:We present constraints on the Mean Matter Density, Omega_m, the normalization of the Density fluctuation power spectrum, sigma_8, and the dark-energy equation-of-state parameter, w, obtained from measurements of the X-ray luminosity function of the largest known galaxy clusters at redshifts z
Robert Schmidt - One of the best experts on this subject based on the ideXlab platform.
-
Weighing the giants – IV. Cosmology and neutrino mass
Monthly Notices of the Royal Astronomical Society, 2014Co-Authors: Adam Mantz, Steven W. Allen, David Rapetti, Patrick L. Kelly, Robert Schmidt, Douglas Applegate, Anja Von Der Linden, R. Glenn Morris, Saroj Adhikari, Mark T. AllenAbstract:We employ robust weak gravitational lensing measurements to improve cosmological constraints from measurements of the galaxy cluster mass function and its evolution, using X-ray selected clusters detected in the ROSAT All-Sky Survey. Our lensing analysis constrains the absolute mass scale of such clusters at the 8 per cent level, including both statistical and systematic uncertainties. Combining it with the survey data and X-ray follow-up observations, we find a tight constraint on a combination of the Mean Matter Density and late-time normalization of the Matter power spectrum, $\sigma_8(\Omega_m/0.3)^{0.17}=0.81\pm0.03$, with marginalized, one-dimensional constraints of $\Omega_m=0.26\pm0.03$ and $\sigma_8=0.83\pm0.04$. For these two parameters, this represents a factor of two improvement in precision with respect to previous work, primarily due to the reduced systematic uncertainty in the absolute mass calibration provided by the lensing analysis. Our new results are in good agreement with constraints from cosmic microwave background (CMB) data, both WMAP and Planck (plus WMAP polarization), under the assumption of a flat $\Lambda$CDM cosmology with minimal neutrino mass. Consequently, we find no evidence for non-minimal neutrino mass from the combination of cluster data with CMB, supernova and baryon acoustic oscillation measurements, regardless of which all-sky CMB data set is used (and independent of the recent claimed detection of B-modes on degree scales). We also present improved constraints on models of dark energy (both constant and evolving), modifications of gravity, and primordial non-Gaussianity. Assuming flatness, the constraints for a constant dark energy equation of state from the cluster data alone are at the 15 per cent level, improving to $\sim 6$ per cent when the cluster data are combined with other leading probes.
-
Measuring cosmic distances with galaxy clusters
arXiv: Cosmology and Nongalactic Astrophysics, 2013Co-Authors: Steven W. Allen, D. Rapetti, A. Von Der Linden, Patrick L. Kelly, D. E. Applegate, A. Mantz, Robert Schmidt, R. G. MorrisAbstract:In addition to cosmological tests based on the mass function and clustering of galaxy clusters, which probe the growth of cosmic structure, nature offers two independent ways of using clusters to measure cosmic distances. The first uses measurements of the X-ray emitting gas mass fraction, which is an approximately standard quantity, independent of mass and redshift, for the most massive clusters. The second uses combined millimeter (mm) and X-ray measurements of cluster pressure profiles. We review these methods, their current status and the prospects for improvements over the next decade. For the first technique, which currently provides comparable dark energy constraints to type Ia supernova studies, improvements of a factor of 6 or more should be readily achievable, together with tight constraints on the Mean Matter Density that are largely independent of the cosmological model assumed. Realizing this potential will require a coordinated, multiwavelength approach, utilizing new cluster surveys, X-ray, optical and mm facilities, and a continued emphasis on improved hydrodynamical simulations.
-
Improved constraints on dark energy from Chandra X-ray observations of the largest relaxed galaxy clusters
Monthly Notices of the Royal Astronomical Society, 2007Co-Authors: Steven W. Allen, Harald Ebeling, David Rapetti, Robert Schmidt, R. G. Morris, Andrew C. FabianAbstract:We present constraints on the Mean Matter Density, � m, dark energy Density, � DE, and the dark energy equation of state parameter, w, using Chandra measurements of the X-ray gas mass fraction (fgas )i n 42 hot (kT > 5 keV), X-ray luminous, dynamically relaxed galaxy clusters spanning the redshift range 0.05 < z < 1.1. Using only the fgas data for the six lowest redshift clusters at z < 0.15, for which dark energy has a negligible effect on the measurements, we measurem = 0.28 ± 0.06 (68 per cent confidence limits, using standard priors on the Hubble constant, H0, and Mean baryon Density, � b h 2 ). Analysing the data for all 42 clusters, employ- ing only weak priors on H0 andb h 2 , we obtain a similar result onm and a detection of the effects of dark energy on the distances to the clusters at ∼99.99 per cent confidence, with � DE = 0.86 ± 0.21 for a non-flatCDM model. The detection of dark energy is comparable in significance to recent type Ia supernovae (SNIa) studies and represents strong, independent evidence for cosmic acceleration. Systematic scatter remains undetected in the fgas data, despite a weighted Mean statistical scatter in the distance measurements of only ∼5 per cent. For a flat cosmology with a constant dark energy equation of state, we measurem = 0.28 ± 0.06 and w =− 1.14 ± 0.31. Combining the fgas data with independent constraints from cosmic mi- crowave background and SNIa studies removes the need for priors onb h 2 and H0 and leads to tighter constraints: � m = 0.253 ± 0.021 and w =− 0.98 ± 0.07 for the same constant-w model. Our most general analysis allows the equation of state to evolve with redshift. Marginalizing over possible transition redshifts 0.05 < zt < 1, the combined fgas + CMB + SNIa data set constrains the dark energy equation of state at late and early times to be w0 =− 1.05 ± 0.29 and wet =− 0.83 ± 0.46, respectively, in agreement with the cosmological constant paradigm. Relaxing the assumption of flatness weakens the constraints on the equation of state by only a factor of ∼2. Our analysis includes conservative allowances for systematic uncertainties as- sociated with instrument calibration, cluster physics and data modelling. The measured small systematic scatter, tight constraint onm and powerful constraints on dark energy from the fgas data bode well for future dark energy studies using the next generation of powerful X-ray observatories, such as Constellation-X.
-
Constraints on dark energy from Chandra observations of the largest relaxed galaxy clusters
Monthly Notices of the Royal Astronomical Society, 2004Co-Authors: Steven W. Allen, Harald Ebeling, Robert Schmidt, Andrew C. Fabian, L. Van SpeybroeckAbstract:We present constraints on the Mean Matter Density, {Omega}{sub m}, dark energy Density, {Omega}{sub DE}, and the dark energy equation of state parameter, w, using Chandra measurements of the X-ray gas mass fraction (fgas) in 42 hot (kT > 5keV), X-ray luminous, dynamically relaxed galaxy clusters spanning the redshift range 0.05 < z < 1.1. Using only the fgas data for the 6 lowest redshift clusters at z < 0.15, for which dark energy has a negligible effect on the measurements, we measure {Omega}{sub m}=0.28{+-}0.06 (68% confidence, using standard priors on the Hubble Constant, H{sub 0}, and Mean baryon Density, {Omega}{sub b}h{sup 2}). Analyzing the data for all 42 clusters, employing only weak priors on H{sub 0} and {Omega}{sub b}h{sup 2}, we obtain a similar result on {Omega}{sub m} and detect the effects of dark energy on the distances to the clusters at {approx}99.99% confidence, with {Omega}{sub DE}=0.86{+-}0.21 for a non-flat LCDM model. The detection of dark energy is comparable in significance to recent SNIa studies and represents strong, independent evidence for cosmic acceleration. Systematic scatter remains undetected in the f{sub gas} data, despite a weighted Mean statistical scatter in the distance measurements of only {approx}5%. For a flat cosmology with constant w, we measure {Omega}{sub m}=0.28{+-}0.06 and w=-1.14{+-}0.31. Combining the fgas data with independent constraints from CMB and SNIa studies removes the need for priors on {Omega}{sub b}h{sup 2} and H{sub 0} and leads to tighter constraints: {Omega}{sub m}=0.253{+-}0.021 and w=-0.98{+-}0.07 for the same constant-w model. More general analyses in which we relax the assumption of flatness and/or allow evolution in w remain consistent with the cosmological constant paradigm. Our analysis includes conservative allowances for systematic uncertainties. The small systematic scatter and tight constraints bode well for future dark energy studies using the f{sub gas} method.
-
A preference for a non-zero neutrino mass from cosmological data
Monthly Notices of the Royal Astronomical Society, 2003Co-Authors: Steven W. Allen, Robert Schmidt, Sarah BridleAbstract:We present results from the analysis of cosmic microwave background (CMB), large-scale structure (galaxy redshift survey) and X-ray galaxy cluster (baryon fraction and X-ray luminosity function) data, assuming a geometrically flat cosmological model and allowing for tensor components and a non-negligible neutrino mass. From a combined analysis of all data, assuming three degenerate neutrino species, we measure a contribution of neutrinos to the energy Density of the Universe, Omega(nu)h(2) = 0.0059(-0.0027)(+0.0033) (68 per cent confidence limits), with zero falling on the 99 per cent confidence limit. This corresponds to similar to4 per cent of the total mass Density of the Universe and implies a species-summed neutrino mass Sigma(i)m(i) = 0.56(-0.26)(+0.30) eV, or m(nu) similar to 0.2 eV per neutrino. We examine possible sources of systematic uncertainty in the results. Combining the CMB, large-scale structure and cluster baryon fraction data, we measure an amplitude of mass fluctuations on 8 h(-1) Mpc scales of sigma(8) = 0.74(-0.07)(+0.12), which is consistent with measurements based on the X-ray luminosity function and other studies of the number Density and evolution of galaxy clusters. This value is lower than that obtained when fixing a negligible neutrino mass (sigma(8) = 0.86(-0.07)(+0.08)). The combination of CMB, large-scale structure and cluster baryon fraction data also leads to remarkably tight constraints on the Hubble constant, H-0 = 68.4(-1.4)(+2.0) km s(-1) Mpc(-1), Mean Matter Density, Omega(m) = 0.31 +/- 0.02, and physical baryon Density, Omega(b) h(2) = 0.024 +/- 0.001, of the Universe.
Adam Mantz - One of the best experts on this subject based on the ideXlab platform.
-
New constraints on f(R) gravity from clusters of galaxies
Physical Review D, 2015Co-Authors: Matteo Cataneo, Adam Mantz, Steven W. Allen, David Rapetti, Patrick L. Kelly, Fabian Schmidt, Douglas Applegate, Anja Von Der Linden, R. Glenn MorrisAbstract:The abundance of massive galaxy clusters is a powerful probe of departures from general relativity (GR) on cosmic scales. Despite current stringent constraints placed by stellar and galactic tests, on larger scales alternative theories of gravity such as $f(R)$ can still work as effective theories. Here we present constraints on two popular models of $f(R)$, Hu-Sawicki and ``designer,'' derived from a fully self-consistent analysis of current samples of x-ray selected clusters and accounting for all the covariances between cosmological and astrophysical parameters. Using cluster number counts in combination with recent data from the cosmic microwave background (CMB) and the CMB lensing potential generated by large scale structures, as well as with other cosmological constraints on the background expansion history and its Mean Matter Density, we obtain the upper bounds ${\mathrm{log}}_{10}|{f}_{R0}|l4.79$ and ${\mathrm{log}}_{10}{B}_{0}l3.75$ at the 95.4% confidence level, for the Hu-Sawicki (with $n=1$) and designer models, respectively. The robustness of our results derives from high-quality cluster growth data for the most massive clusters known out to redshifts $z\ensuremath{\sim}0.5$, a tight control of systematic uncertainties including an accurate and precise mass calibration from weak gravitational lensing data, and the use of the full shape of the halo mass function over the mass range of our data.
-
Weighing the giants – IV. Cosmology and neutrino mass
Monthly Notices of the Royal Astronomical Society, 2014Co-Authors: Adam Mantz, Steven W. Allen, David Rapetti, Patrick L. Kelly, Robert Schmidt, Douglas Applegate, Anja Von Der Linden, R. Glenn Morris, Saroj Adhikari, Mark T. AllenAbstract:We employ robust weak gravitational lensing measurements to improve cosmological constraints from measurements of the galaxy cluster mass function and its evolution, using X-ray selected clusters detected in the ROSAT All-Sky Survey. Our lensing analysis constrains the absolute mass scale of such clusters at the 8 per cent level, including both statistical and systematic uncertainties. Combining it with the survey data and X-ray follow-up observations, we find a tight constraint on a combination of the Mean Matter Density and late-time normalization of the Matter power spectrum, $\sigma_8(\Omega_m/0.3)^{0.17}=0.81\pm0.03$, with marginalized, one-dimensional constraints of $\Omega_m=0.26\pm0.03$ and $\sigma_8=0.83\pm0.04$. For these two parameters, this represents a factor of two improvement in precision with respect to previous work, primarily due to the reduced systematic uncertainty in the absolute mass calibration provided by the lensing analysis. Our new results are in good agreement with constraints from cosmic microwave background (CMB) data, both WMAP and Planck (plus WMAP polarization), under the assumption of a flat $\Lambda$CDM cosmology with minimal neutrino mass. Consequently, we find no evidence for non-minimal neutrino mass from the combination of cluster data with CMB, supernova and baryon acoustic oscillation measurements, regardless of which all-sky CMB data set is used (and independent of the recent claimed detection of B-modes on degree scales). We also present improved constraints on models of dark energy (both constant and evolving), modifications of gravity, and primordial non-Gaussianity. Assuming flatness, the constraints for a constant dark energy equation of state from the cluster data alone are at the 15 per cent level, improving to $\sim 6$ per cent when the cluster data are combined with other leading probes.
-
A combined measurement of cosmic growth and expansion from clusters of galaxies, the CMB and galaxy clustering
Monthly Notices of the Royal Astronomical Society, 2013Co-Authors: David Rapetti, Adam Mantz, Steven W. Allen, Chris Blake, David Parkinson, Florian BeutlerAbstract:Combining galaxy cluster data from the ROSAT All-Sky Survey and the Chandra Xray Observatory, cosmic microwave background data from the Wilkinson Microwave Anisotropy Probe, and galaxy clustering data from the WiggleZ Dark Energy Survey, the 6-degree Field Galaxy Survey and the Sloan Digital Sky Survey III, we test for consistency the cosmic growth of structure predicted by General Relativity (GR) and the cosmic expansion history predicted by the cosmological constant plus cold dark Matter paradigm (�CDM). The combination of these three independent, well studied measurements of the evolution of the Mean energy Density and its fluctuations is able to break strong degeneracies between model parameters. We model the key properties of cosmic growth with the normalization of the Matter power spectrum, σ8, and the cosmic growth index, γ, and those of cosmic expansion with the Mean Matter Density, m, the Hubble constant, H0, and a kinematical parameter equivalent to that for the dark energy equation of state, w. For a spatially flat geometry, w = −1, and allowing for systematic uncertainties, we obtain σ8 = 0.785± 0.019 and γ = 0.570 +0.064 0.063 (at the 68.3 per cent confidence level). Allowing both w and γ to vary we find w = −0.950 +0.069 0.070 and γ = 0.533 ± 0.080. To further tighten the constraints on the expansion parameters, we also include supernova, Cepheid variable and baryon acoustic oscillation data. For w = −1, we have γ = 0.616±0.061. For our most general model with a free w, we measure m = 0.278 +0.012 0.011 , H0 = 70.0 ± 1.3 km s 1 Mpc 1 and w = −0.987 +0.054 0.053 for the expansion parameters, and σ8 = 0.789 ± 0.019 and γ = 0.604±0.078 for the growth parameters. These results are in excellent agreement with GR+�CDM (γ ≃ 0.55; w = −1) and represent the tightest and most robust simultaneous constraint on cosmic growth and expansion to date.
-
Constraints on modified gravity from the observed X-ray luminosity function of galaxy clusters
Monthly Notices of the Royal Astronomical Society, 2009Co-Authors: David Rapetti, Adam Mantz, Steven W. Allen, Harald EbelingAbstract:We use measurements of the growth of cosmic structure, as inferred from the observed evolution of the X-ray luminosity function (XLF) of galaxy clusters, to constrain departures from General Relativity (GR) on cosmological scales. We employ the popular growth rate parameterization, Omega_m(z)^gamma, for which GR predicts a growth index gamma~0.55. We use observations of the cosmic microwave background (CMB), type Ia supernovae (SNIa), and X-ray cluster gas-mass fractions (fgas), to simultaneously constrain the expansion history and energy content of the Universe, as described by the background model parameters: Omega_m, w, and Omega_k, i.e., the Mean Matter Density, the dark energy equation of state parameter, and the Mean curvature, respectively. Using conservative allowances for systematic uncertainties, in particular for the evolution of the mass-luminosity scaling relation in the XLF analysis, we find gamma=0.51+0.16-0.15 and Omega_m=0.27+-0.02 (68.3 per cent confidence limits), for a flat cosmological constant (LCDM) background model. Allowing w to be a free parameter, we find gamma=0.44+0.17-0.15. Relaxing the flatness prior in the LCDM model, we obtain gamma=0.51+0.19-0.16. When in addition to the XLF data we use the CMB data to constrain gamma through the ISW effect, we obtain a combined constraint of gamma=0.45+0.14-0.12 for the flat LCDM model. Our analysis provides the tightest constraints to date on the growth index. We find no evidence for departures from General Relativity on cosmological scales.
-
New constraints on dark energy from the observed growth of the most X-ray luminous galaxy clusters
Monthly Notices of the Royal Astronomical Society, 2008Co-Authors: Adam Mantz, Steven W. Allen, Harald Ebeling, David RapettiAbstract:We present constraints on the Mean Matter Density, Omega_m, the normalization of the Density fluctuation power spectrum, sigma_8, and the dark-energy equation-of-state parameter, w, obtained from measurements of the X-ray luminosity function of the largest known galaxy clusters at redshifts z
Michal Chodorowski - One of the best experts on this subject based on the ideXlab platform.
-
Influence of the Local Void on measurements of the clustering dipole
Monthly Notices of the Royal Astronomical Society, 2010Co-Authors: Maciej Bilicki, Michal ChodorowskiAbstract:In measurements of the clustering dipole from all-sky surveys, an important problem is the lack of information about galaxy distribution in the so-called zone of avoidance (ZoA). The existence of the Local Void (LV) has a systematic effect on these measurements. If the ZoA is randomly filled with mock galaxies, then the calculated acceleration of the Local Group (LG) of galaxies has a spurious component, resulting from the lack of real galaxies in the intersection of the LV with the ZoA. This component affects both the misalignment angle between the clustering dipole and the CMB dipole, and the inferred value of Mean Matter Density Ω m . We calculate the amplitude of the spurious acceleration acting on the LG due to the LV. Its value depends on the geometry and size of the LV, as well as on its Density contrast. However, under the simplest assumption of the LV being spherical and completely empty, within the linear theory this amplitude amounts only to about 45 km s -1 in units of velocity. The resulting change in the misalignment angle is smaller than 1°, and the fractional change in the deduced value of Ω m is about 5 per cent. Accounting for observationally indicated elongation of the LV and maintaining the maximizing assumption of a complete lack of galaxies inside increases these numbers only moderately. Specifically, the amplitude of the spurious acceleration rises to about 60 km s -1 , the misalignment angle remains still smaller than 1° and the fractional change in the deduced value of Ω m is enhanced to about 7 per cent. Thus, despite the overall importance of the LV for the motion of the LG, the influence of the intersection of the LV with the ZoA on measurements of the clustering dipole is found to be only a minor systematic effect.
-
Influence of the Local Void on measurements of the clustering dipole
Monthly Notices of the Royal Astronomical Society, 2010Co-Authors: Maciej Bilicki, Michal ChodorowskiAbstract:In measurements of the clustering dipole from all-sky surveys, an important problem is the lack of information about galaxy distribution in the so-called Zone of Avoidance (ZoA). The existence of the Local Void (LV) has a systematic effect on these measurements. If the ZoA is randomly filled with mock galaxies, then the calculated acceleration of the Local Group of galaxies (LG) has a spurious component, resulting from the lack of real galaxies in the intersection of the LV with the ZoA. This component affects both the misalignment angle between the clustering dipole and the CMB dipole, and the inferred value of Mean Matter Density Omega_m. We calculate the amplitude of the spurious acceleration acting on the LG due to the LV. Its value depends on the geometry and size of the LV, as well as on its Density contrast. However, under the simplest assumption of the LV being spherical and completely empty, within the linear theory this amplitude amounts only to about 45 km/s in units of velocity. The resulting change in the misalignment angle is smaller than 1 degree, and the fractional change in the deduced value of Omega_m is about 5%. Accounting for observationally indicated elongation of the LV and maintaining the maximising assumption of a complete lack of galaxies inside increases these numbers only moderately. Specifically, the amplitude of the spurious acceleration rises to about 60 km/s, the misalignment angle remains still smaller than 1 degree, and the fractional change in the deduced value of Omega_m is enhanced to about 7%. Thus, despite the overall importance of the Local Void for the motion of the Local Group, the influence of the intersection of the LV with the ZoA on measurements of the clustering dipole is found to be only a minor systematic effect.Comment: 6 pages, 2 figures; revised version, slightly expanded, accepted for publication in MNRAS