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# Scaling relation between Sunyaev–Zel’dovich effect and X-ray luminosity and scale-free evolution of cosmic baryon field

Department of Astronomy, Beijing Normal University, Beijing 100875, PR China; Key Laboratory of Particle Astrophysics, Institute of High Energy Physics, Chinese Academy of Sciences, P.O. Box 918-3, Beijing 100049, PR China; Kavli Institute for Theoretical Physics China, Institute of Theoretical Physics, Chinese Academy of Sciences (KITPC/ITP-CAS), P.O. Box 2735, Beijing 100080, PR China; Department of Physics, University of Arizona, Tucson AZ 85721, United States; Purple Mountain Observatory, Nanjing 210008, PR China; National Astronomical Observatories, Chinese Academy of Science, Chao-Yang District, Beijing 100012, PR China; Beijing Planetarium, Beijing 100044, PR China

New Astronomy (Impact Factor: 1.85). 07/2008; DOI: 10.1016/j.newast.2008.07.004 Source: arXiv

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**ABSTRACT:**Using Wilkinson Microwave Anisotropy Probe (WMAP) five year data, we look for the average Sunyaev–Zel'dovich effect (SZE) signal from clusters of galaxies by stacking the regions around hundreds of known X-ray clusters. We detect the average SZE at a very high significance level. The average cluster signal is spatially resolved in the W band. This mean signal is compared with the expected signal from the same clusters calculated on the basis of archival ROSAT data. From the comparison, we conclude that the observed SZE seems to be less than the expected signal derived from X-ray measurements when a standard β-model is assumed for the gas distribution. This conclusion is model dependent. Our predictions depend mostly on the assumptions made about the core radius of clusters and the slope of the gas density profile. Models with steeper profiles are able to simultaneously fit both X-ray and WMAP data better than a β-model. However, the agreement is not perfect and we find that it is still difficult to make the X-ray and SZE results agree. A model assuming point source contamination in SZE clusters provides a better fit to the one-dimensional SZE profiles, thus suggesting that contamination from point sources could be contributing to a diminution of the SZE signal. Selecting a model that better fits both X-ray and WMAP data away from the very central region, we estimate the level of contamination and find that on average, the point source contamination is on the level of 16 mJy (at 41 GHz), 26 mJy (at 61 GHz) and 18 mJy (at 94 GHz). These estimated fluxes are marginally consistent with the estimated contamination derived from radio and infrared surveys, thus suggesting that the combination of a steeper gas profile and the contribution from point sources allows us to consistently explain the X-ray emission and SZE in galaxy clusters as measured by both ROSAT and WMAP.Monthly Notices of the Royal Astronomical Society 12/2009; 402(2):1179 - 1194. · 5.52 Impact Factor - [Show abstract] [Hide abstract]

**ABSTRACT:**We develop an analytic framework to understand fragmentation in turbulent, self-gravitating media. Previously, we showed some properties of turbulence can be predicted with the excursion-set formalism. Here, we generalize to fully time-dependent gravo-turbulent fragmentation & collapse. We show that turbulent systems are always gravitationally unstable (in a probabilistic sense). The fragmentation mass spectra, size/mass relations, correlation functions, range of scales over which fragmentation occurs, & time-dependent rates of fragmentation are predictable. We show how this depends on bulk turbulent properties (Mach numbers & power spectra). We also generalize to include rotation, complicated equations of state, collapsing/expanding backgrounds, magnetic fields, intermittency, & non-normal statistics. We derive how fragmentation is suppressed with 'stiffer' equations of state or different driving mechanisms. Suppression appears at an 'effective sonic scale' where Mach(R,rho)~1. Gas becomes stable below this scale for polytropic gamma>4/3, but fragmentation still occurs on larger scales. The scale-free nature of turbulence and gravity generically drives mass spectra and correlation functions towards universal shapes, with weak dependence on many properties of the media. Correlated fluctuation structures, non-Gaussian density distributions, & intermittency have surprisingly small effects on the fragmentation process. This is because fragmentation cascades on small scales are 'frozen in' when large-scale modes push the 'parent' region above the collapse threshold; though they collapse, their statistics are only weakly modified by the collapse process. With thermal support, structure develops 'top-down' in time via fragmentation cascades; but strong rotational support reverses this to 'bottom-up' growth via mergers & introduces a maximal instability scale distinct from the Toomre scale.Monthly Notices of the Royal Astronomical Society 10/2012; 430(3). · 5.52 Impact Factor -
##### Article: Dynamical effect of the turbulence of the intergalactic medium on the baryon fraction distribution

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**ABSTRACT:**We investigate the dynamical effect of turbulence in the baryonic intergalactic medium (IGM) on the baryon fraction distribution. In the fully developed non-linear regime, the IGM will evolve into a state of turbulence, containing strong and curved shocks, vorticity and complex structures. Turbulence would mean that the density and velocity fields of the IGM would be different from those of the underlying collisionless dark matter. Consequently, the baryon fraction fb will deviate from its cosmic mean fcosmicb. We study these phenomena with simulation samples produced by the weighted essentially non-oscillatory (weno) hybrid cosmological hydrodynamic/N-body code, which is effective for capturing shocks and complex structures. We find that the distribution of the baryon fraction is highly non-uniform on scales from hundreds of kpc to a few Mpc, and fb varies from as low as 1 per cent to a few times the cosmic mean. We further show that the turbulence pressure in the IGM is weakly scale-dependent and comparable to the gravitational energy density of haloes with mass around 1011 h−1 M⊙. The baryon fraction in haloes with mass equal to or smaller than 1011 h−1 M⊙ should be substantially lower than fcosmicb. Numerical results show that fb is decreasing from 0.8fcosmicb at halo mass scales around 1012 h−1 M⊙ to 0.3fcosmicb at 1011 h−1 M⊙ and shows further decrease when halo mass is less than 1011 h−1 M⊙. The strong mass dependence of fb is similar to the observed results. Although the simulated fb in haloes are higher than the observed value by a factor of 2, the turbulence of the IGM should be an important dynamical reason for the remarkable lack of baryonic matter in haloes with mass ≤1012 h−1 M⊙.Monthly Notices of the Royal Astronomical Society 06/2011; 415(2):1093 - 1104. · 5.52 Impact Factor

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