Monthly Notices of the Royal Astronomical Society, 2014
ABSTRACT In light of the tension in cosmological constraints reported by the Planck team between ... more ABSTRACT In light of the tension in cosmological constraints reported by the Planck team between their SZ-selected cluster counts and Cosmic Microwave Background (CMB) temperature anisotropies, we compare the Planck cluster mass estimates with robust, weak-lensing mass measurements from the Weighing the Giants (WtG) project. For the 22 clusters in common between the Planck cosmology sample and WtG, we find an overall mass ratio of $\left< M_{Planck}/M_{\rm WtG} \right> = 0.688 \pm 0.072$. Extending the sample to clusters not used in the Planck cosmology analysis yields a consistent value of $\left< M_{Planck}/M_{\rm WtG} \right> = 0.698 \pm 0.062$ from 38 clusters in common. Identifying the weak-lensing masses as proxies for the true cluster mass (on average), these ratios are $\sim 1.6\sigma$ lower than the default mass bias of 0.8 assumed in the Planck cluster analysis. Adopting the WtG weak-lensing-based mass calibration would substantially reduce the tension found between the Planck cluster count cosmology results and those from CMB temperature anisotropies. We also find modest evidence (at 95 per cent confidence) for a mass dependence of the calibration ratio and discuss its potential origin in light of systematic uncertainties in the temperature calibration of the X-ray measurements used to calibrate the Planck cluster masses. Our results exemplify the critical role that robust absolute mass calibration plays in cluster cosmology, and the invaluable role of accurate weak-lensing mass measurements in this regard.
Mon. Not. R. Astron. Soc. 000, 000000 (0000) Printed October 6, 2010 (MN LATEX style file v2.2) ... more Mon. Not. R. Astron. Soc. 000, 000000 (0000) Printed October 6, 2010 (MN LATEX style file v2.2) ... Extreme AGN Feedback and Cool Core Destruction in the X-ray ... S. Ehlert,1⋆ SW Allen,1 A. von der Linden,1 A. Simionescu,1 N. Werner,1 GB Taylor,2
Chandra is a key instrument to understand the physics and evolution of galaxy clusters. But the c... more Chandra is a key instrument to understand the physics and evolution of galaxy clusters. But the combination with other high-quality, multi-wavelength observations is arguably even more powerful. We are conducting a multi-wavelength follow-up survey of 30 of the most massive clusters known at z=0.3-0.6, selected from the MAssive Clusters Survey (MACS). Our follow-up data consists of Chandra X-ray imaging, deep multi-color imaging from SuprimeCam and HST imaging. The weak lensing mass measurements derived from the optical imaging will be a vital ingredient to determine the non-thermal pressure component in clusters, and thus to calibrate them as cosmological probes. At the same time, the multi-wavelength data allows us to study intriguing clusters in more detail, e.g. to study the physics of merging clusters. I will present our first results, and highlight some of the most intriguing clusters, such as the cousin of the Bullet Cluster, MACSJ0025.4-1222.
Monthly Notices of the Royal Astronomical Society, 2014
ABSTRACT In light of the tension in cosmological constraints reported by the Planck team between ... more ABSTRACT In light of the tension in cosmological constraints reported by the Planck team between their SZ-selected cluster counts and Cosmic Microwave Background (CMB) temperature anisotropies, we compare the Planck cluster mass estimates with robust, weak-lensing mass measurements from the Weighing the Giants (WtG) project. For the 22 clusters in common between the Planck cosmology sample and WtG, we find an overall mass ratio of $\left< M_{Planck}/M_{\rm WtG} \right> = 0.688 \pm 0.072$. Extending the sample to clusters not used in the Planck cosmology analysis yields a consistent value of $\left< M_{Planck}/M_{\rm WtG} \right> = 0.698 \pm 0.062$ from 38 clusters in common. Identifying the weak-lensing masses as proxies for the true cluster mass (on average), these ratios are $\sim 1.6\sigma$ lower than the default mass bias of 0.8 assumed in the Planck cluster analysis. Adopting the WtG weak-lensing-based mass calibration would substantially reduce the tension found between the Planck cluster count cosmology results and those from CMB temperature anisotropies. We also find modest evidence (at 95 per cent confidence) for a mass dependence of the calibration ratio and discuss its potential origin in light of systematic uncertainties in the temperature calibration of the X-ray measurements used to calibrate the Planck cluster masses. Our results exemplify the critical role that robust absolute mass calibration plays in cluster cosmology, and the invaluable role of accurate weak-lensing mass measurements in this regard.
Mon. Not. R. Astron. Soc. 000, 000000 (0000) Printed October 6, 2010 (MN LATEX style file v2.2) ... more Mon. Not. R. Astron. Soc. 000, 000000 (0000) Printed October 6, 2010 (MN LATEX style file v2.2) ... Extreme AGN Feedback and Cool Core Destruction in the X-ray ... S. Ehlert,1⋆ SW Allen,1 A. von der Linden,1 A. Simionescu,1 N. Werner,1 GB Taylor,2
Chandra is a key instrument to understand the physics and evolution of galaxy clusters. But the c... more Chandra is a key instrument to understand the physics and evolution of galaxy clusters. But the combination with other high-quality, multi-wavelength observations is arguably even more powerful. We are conducting a multi-wavelength follow-up survey of 30 of the most massive clusters known at z=0.3-0.6, selected from the MAssive Clusters Survey (MACS). Our follow-up data consists of Chandra X-ray imaging, deep multi-color imaging from SuprimeCam and HST imaging. The weak lensing mass measurements derived from the optical imaging will be a vital ingredient to determine the non-thermal pressure component in clusters, and thus to calibrate them as cosmological probes. At the same time, the multi-wavelength data allows us to study intriguing clusters in more detail, e.g. to study the physics of merging clusters. I will present our first results, and highlight some of the most intriguing clusters, such as the cousin of the Bullet Cluster, MACSJ0025.4-1222.
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