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>How far do they go? The outer structure of dark matter halos
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How far do they go? The outer structure of dark matter halos
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机译：他们走了多远？暗物质晕的外部结构
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摘要
We study the density profiles of collapsed galaxy-size dark matter halos withmasses 1e11-5e12 Msun focusing mostly on the halo outer regions from the formalvirial radius Rvir up to 5-7Rvir. We find that isolated halos in this massrange extend well beyond Rvir exhibiting all properties of virialized objectsup to 2-3Rvir: relatively smooth density profiles and no systematic infallvelocities. The dark matter halos in this mass range do not grow as one naivelymay expect through a steady accretion of satellites, i.e., on average there isno mass infall. This is strikingly different from more massive halos, whichhave large infall velocities outside of the virial radius. We provide accuratefit for the density profile of these galaxy-size halos. For a wide range(0.01-2)Rvir of radii the halo density profiles are fit with the approximationrho=rho_s exp(-2n[x^{1/n}-1])+rho_m, where x=r/r_s, rho_m is the mean matterdensity of the Universe, and the index n is in the range n=6-7.5. Theseprofiles do not show a sudden change of behavior beyond the virial radius. Forlarger radii we combine the statistics of the initial fluctuations with thespherical collapse model to obtain predictions for the mean and most probabledensity profiles for halos of several masses. The model give excellent resultsbeyond 2-3 formal virial radii.
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