Galaxy Formation on Caustics

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Session 115 -- Cosmology and Dark Matter
Oral presentation, Saturday, January 15, 10:15-11:45, Salon III Room (Crystal Gateway)

[115.03] Galaxy Formation on Caustics

Nick Gnedin (Princeton University Observatory)

The simple model for galaxy formation during the evolution of large-scale structure is proposed. The model is designed to separate sharply galaxy formation on peaks and on pancakes and filaments. The two-component (dark matter plus baryonic fluid) cosmological code in PM-implementation is supplemented with the gravitational instability criteria which is based on the approximate solution to the nonstationary virial equations at each particle in the simulation. The local geometry, determined according to the eigenvalues of the deformation tensor, is assumed to be either 3D, 2D or 1D spheres. The approximate solution to the virial equations then gives an estimate to the collapse time of an object.

The simulation of standard CDM and CDM plus cosmological constant models show that the 3D compact objects with masses in a range $10^9-10^{10} \msun$ form at early redshifts $z\sim2-5$, and 1D and 2D objects with masses from $10^9\msun$ up to $10^{12} \msun$ form at $z\la2$ with the low-mass objects forming quite recently.

Extensive tests show yet that the proposed approach is severely resolution dependent and only qualitative features of the simulation can be considered reliable. Thus, lagrangian code is required in order to obtain reliable quantitative information about the galaxy formation in the proposed approach.


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