A New Robust Low-Scatter X-ray Mass Indicator for Clusters of Galaxies

University of Chicago, Chicago, Illinois, United States
The Astrophysical Journal (Impact Factor: 5.99). 03/2006; 650(1). DOI: 10.1086/506319
Source: arXiv


We present comparison of X-ray proxies for the total cluster mass, including the spectral temperature (Tx), gas mass measured within r500 (Mg), and the new proxy, Yx, which is a simple product of Tx and Mg and is related to the total thermal energy of the ICM. We use mock Chandra images constructed for a sample of clusters simulated with the eulerian N-body+gasdynamics adaptive mesh refinement ART code in the concordance LCDM cosmology. The simulations achieve high spatial and mass resolution and include radiative cooling, star formation, and other processes accompanying galaxy formation. Our analysis shows that simulated clusters exhibit a high degree of regularity and tight correlations between the considered observables and total mass. The normalizations of the M-Tx, Mg-Tx, and M-Yx relations agree to better than 10-15% with the current observational measurements of these relations. Our results show that Yx is the best mass proxy with a remarkably low scatter of only ~5-7% in M500 for a fixed Yx, at both low and high redshifts and regardless of whether clusters are relaxed or not. In addition, we show that redshift evolution of the Yx-M500 relation is close to the self-similar prediction, which makes Yx a very attractive mass indicator for measurements of the cluster mass function from X-ray selected samples. Comment: submitted to ApJ; 9 pages, 6 figures, uses emulateapj

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Available from: Daisuke Nagai, Oct 30, 2012
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    • "The spectroscopically determined ICM temperature thus turns out to be one of the best mass proxies as single observable parameter (e.g. Kravtsov et al. 2006). The tightest relations are obtained, if the core regions are excluded in the global temperature measurement, due to the disproportionate influence of the central CCs as will become apparent below, and it has thus become standard to quote the mean temperature in the radial region r = 0.15−1×r 500 as the most reliable single observable mass proxy for clusters (e.g. "
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    ABSTRACT: Wilkinson Microwave Anisotropy Probe (WMAP) has provided us with the yet highest resolution all-sky maps of the Cosmic Microwave Background. As a result of thermal Sunyaev-Zel'dovich effect, clusters of galaxies are imprinted as tiny, poorly resolved dips on top of primary CMB anisotropies in these maps. Here, I describe different efforts to extract the physics of Intracluster Medium (ICM) from the sea of primary CMB, through combining WMAP with low-redshift galaxy or X-ray cluster surveys. This finally culminates at a mean (universal) ICM pressure profile, which is for the first time directly constrained from WMAP 3yr maps, and leads to interesting constraints on the ICM baryonic budget. Comment: 9 pages and 4 figures; Proceedings of the Fundamental Physics With CMB workshop, UC Irvine, March 23-25, 2006, to be published in New Astronomy Reviews
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