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تسجيل مستخدم جديدHalo Assembly Bias in the Quasi-linear Regime
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We address the question of whether or not assembly bias arises in the absence of highly non-linear effects such as tidal stripping of halos near larger mass concentrations. Therefore, we use a simplified dynamical scheme where these effects are not modeled. We choose the punctuated Zeldovich (PZ) approximation, which prevents orbit mixing by coalescing particles coming within a critical distance of each other. A numerical implementation of this approximation is fast, allowing us to run a large number of simulations to study assembly bias. We measure an assembly bias from 60 PZ simulations, each with 512^3 cold particles in a 128h^-1 Mpc cubic box. The assembly bias estimated from the correlation functions at separations < 5h^-1 Mpc for objects (halos) at z=0 is comparable to that obtained in full N-body simulations. For masses 4x10^11 h^-1 Mo the oldest 10% haloes are 3-5 times more correlated than the youngest 10%. The bias weakens with increasing mass, also in agreement with full N-body simulations. We find that that halo ages are correlated with the dimensionality of the surrounding linear structures as measured by the parameter (lambda_1+lambda_2+lambda_3)/ (lambda_1^2+lambda_2^2+lambda_3^2)^{1/2} where lambda_i are proportional to the eigenvalues of the velocity deformation tensor. Our results suggest that assembly bias may already be encoded in the early stages of the evolution.
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