LoCuSS: CALIBRATING MASS–OBSERVABLE SCALING RELATIONS FOR CLUSTER COSMOLOGY WITH SUBARU WEAK-LENSING OBSERVATIONS
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Smith, G. P.
cosmology: observations – dark matter – galaxies: clusters: general – gravitational lensing: weak – X-rays: galaxies: clusters
We present a joint weak-lensing/X-ray study of galaxy cluster mass–observable scaling relations motivated by the critical importance of accurate calibration of mass proxies for future X-ray missions, including eROSITA. We use a sample of 12 clusters at z ≃ 0.2 that we have observed with Subaru and XMM-Newton to construct relationships between the weak-lensing mass (M) and three X-ray observables, gas temperature (T), gas mass (Mgas), and quasiintegrated gas pressure (YX), at overdensities of Δ = 2500, 1000, and 500 with respect to the critical density.We find that Mgas at Δ ≼ 1000 appears to be the most promising mass proxy of the three because it has the lowest intrinsic scatter in mass at a fixed observable, σlnM ≃ 0.1, independent of the cluster dynamical state. The scatter in mass at fixed T and YX is a factor of ∼2–3 larger than at fixedMgas, which are indicative of the structural segregation that we find in theM–T andM–YX relationships. Undisturbed clusters are found to be ∼40% and ∼20% more massive than disturbed clusters at fixed T and YX, respectively, at∼2σ significance. In particular, A 1914—a well-known merging cluster—significantly increases the scatter and lowers the normalization of the relation for disturbed clusters. We also investigated the covariance between the intrinsic scatter in M–Mgas and M–T relations, finding that they are positively correlated. This contradicts the adaptive mesh refinement simulations that motivated the idea that YX may be a low-scatter mass proxy, and agrees with more recent smoothed particle hydrodynamic simulations based on the Millennium Simulation. We also propose a method to identify a robust mass proxy based on principal component analysis. The statistical precision of our results is limited by the small sample size and the presence of the extreme merging cluster in our sample. We therefore look forward to studying a larger, more complete sample in the future.
N.O., M.T., and T.F. are supported in part by a Grant-in-Aid from the Ministry of Education, Culture, Sports, Science, and Technology of Japan (N.O.: 20740099; M.T.: 20740119; T.F.: 20540245). Y.-Y.Z. and N.O. acknowledge support by the DFG through the Emmy Noether Research Grant RE 1462/2, through Schwerpunkt Program 1177, and through project B6 “Gravitational Lensing and X-ray Emission by Non-Linear Structures” of Transregional Collaborative Research Centre TRR 33 “The Dark Universe,” and support by the German BMBF through the Verbundforschung under grants 50 OR 0601 and 50 OR 1005. A.F. acknowledges support from BMBF/DLR under grant 50 OR 0207 and MPG. A.F. was partially supported by NASA grant NNX08AX46G to UMBC. K.U. is partially supported by the National Science Council of Taiwan under the grant NSC95-2112-M-001-074-MY2. G.P.S. acknowledges support from the Royal Society. This work is supported by a Grant-in-Aid for the COE Program “Exploring NewScience by Bridging Particle–MatterHierarchy” and theGCOE Program “Weaving Science Web beyond Particle–Matter Hierarchy” in Tohoku University, funded by the Ministry of Education, Science, Sports and Culture of Japan. This work is in part supported by a Grant-in-Aid for Science Research in a Priority Area “Probing the Dark Energy through an Extremely Wide and Deep Survey with Subaru Telescope” (18072001) from the Ministry of Education, Culture, Sports, Science, and Technology of Japan. Y.-Y.Z. and A.F. acknowledge the hospitality of the Tohoku University during their frequent visits. This work is supported in part by the World Premier International Research Center Initiative (WPI Initiative), MEXT, Japan.
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