The Impact of Galaxy Cluster Mergers on Cosmological Parameter Estimation from Surveys of the Sunyaev-Zel'dovich Effect - AstrophysicsReport as inadecuate




The Impact of Galaxy Cluster Mergers on Cosmological Parameter Estimation from Surveys of the Sunyaev-Zel'dovich Effect - Astrophysics - Download this document for free, or read online. Document in PDF available to download.

Abstract: Sensitive surveys of the Cosmic Microwave Background will detect thousands ofgalaxy clusters via the Sunyaev-Zel-dovich SZ effect. Two SZ observables, thecentral or maximum and integrated Comptonization parameters y max and Y, relatein a simple way to the total cluster mass, which allow the construction of massfunctions MFs that can be used to estimate cosmological parameters such asOmega M, sigma 8, and the dark energy parameter w. However, clusters form fromthe mergers of smaller structures, events that can disrupt the equilibrium ofintracluster gas upon which SZ-M relations rely. From a set ofN-body-hydrodynamical simulations of binary cluster mergers, we calculate theevolution of Y and y max over the course of merger events and find that bothparameters are transiently -boosted,- primarily during the first core passage.We then use a semi-analytic technique developed by Randall et al. 2002 toestimate the effect of merger boosts on the distribution functions YF and yF ofY and y max, respectively, via cluster merger histories determined fromextended Press-Schechter PS merger trees. We find that boosts do not inducean overall systematic effect on YFs, and the values of Omega M, sigma 8, and wwere returned to within 2% of values expected from the nonboosted YFs. Theboosted yFs are significantly biased, however, causing Omega M to beunderestimated by 15-45%, sigma 8 to be overestimated by 10-25%, and w to bepushed to more negative values by 25-45%. We confirm that the integrated SZeffect, Y, is far more robust to mergers than y max, as previously reported byMotl et al. 2005 and similarly found for the X-ray equivalent Y X, and weconclude that Y is the superior choice for constraining cosmologicalparameters.



Author: Daniel R. Wik 1, Craig L. Sarazin 1, Paul M. Ricker 2, Scott W. Randall 3 1 University of Virginia, 2 University of Illinois, 3 H

Source: https://arxiv.org/



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