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Can satellites deliver substructures and black holes to inner halo by dynamical friction? | | HongSheng Zhao
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5 Dec 2003 | | Subject: | astro-ph | | Affiliation: | 1,2) ( IoA Cambridge, St. Andrews | | Abstract: | A fully analytical formulation is developed to make dynamical friction modeling more realistic. The rate for a satellite to decay its orbit in a host galaxy halo is often severely overestimated when applying ChandraSekhar’s formula without correcting for the tidal loss of the satellite and the adiabactic growth of the host galaxy potential over the Hubble time. As a satellite decays to the inner and denser region of the host galaxy, the high ambient density speeds up their exchange of energy and angular momentum, but shrinks the Roche lobe of the satellite by tides. Eventually both processes of orbital decay and tidal stripping hang up altogether once the satellite is light enough. These competing processes can be modeled analytically for a satellite if we parametrize the massloss history by an empirical formula. We also incorporate the adiabatic contraction of orbits due to growth of the host potential well. Observed dwarf galaxies often show a finite density core, which determines how much inwards its remnants could be delivered to the host galaxy. Ghost streams or remnant cores or globular clusters of satellites should populate preferentially the outer halo (e.g., the Magellanic stream and the Ursa Minor dwarf), rather than the inner halo (e.g., the Sgr stream and the Omega-cen cluster). Massloss due to strong tides in the inner galaxy also makes it problematic for any small central black holes in nuclei of satellite galaxies to decay in orbit and merge into the center of the host galaxy. | | Source: | arXiv, astro-ph/0312165 | | Services: | Forum | Review | PDF | Favorites | |
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