2008/02/25 by Daniel R. Wik, Craig L. Sarazin, Paul M. Ricker +1
Physics and Astronomy · #Cosmology and Gravitation Theories #Galaxies: Formation, Evolution, Phenomena #Gamma-ray bursts and supernovae #astro-ph
paper · pdf · doi:10.1086/587790
16 pages, 6 figures, Accepted for publication in the Astrophysical Journal
arxiv created 2008/02/25 · openalex publication_date 2008/06/06 · arxiv updated 2009/12/01 · openalex created_date 2016/06/24 · openalex updated_date 2026/07/31
Sensitive surveys of the cosmic microwave background will detect thousands of galaxy clusters via the Sunyaev-Zel'dovich (SZ) effect. Two SZ observables, the central or maximum and integrated Comptonization parameters y max and Y , relate in a simple way to the total cluster mass, which allows the construction of mass functions (MFs) that can be used to estimate cosmological parameters such as Ω M , σ 8 , and the dark energy parameter w . However, clusters form from the mergers of smaller structures, events that can disrupt the equilibrium of intracluster gas on which SZ- M relations rely. From a set of N -body/hydrodynamical simulations of binary cluster mergers, we calculate the evolution of Y and y max over the course of merger events and find that both parameters are transiently "boosted," primarily during the first core passage. We then use a semianalytic technique developed by Randall et al. to estimate the effect of merger boosts on the distribution functions YF and yF of Y and y max , respectively, via cluster merger histories determined from extended Press-Schechter (PS) merger trees. We find that boosts do not induce an overall systematic effect on YFs, and the values of Ω M , σ 8 , and w were returned to within 2% of values expected from the nonboosted YFs. The boosted yFs are significantly biased, however, causing Ω M to be underestimated by 15%-45%, σ 8 to be overestimated by 10%-25%, and w to be pushed to more negative values by 25%-45%. We confirm that the integrated SZ effect, Y , is far more robust to mergers than y max , as previously reported by Motl et al. and similarly found for the X-ray equivalent Y X , and we conclude that Y is the superior choice for constraining cosmological parameters.