| Author(s): | Just, A. |
| Title: | Dynamical friction of massive objects in galactic centres |
| Source: | submitted to Mon. Not. R. Astron. Soc. |
| Year: | 2003 |
| Abstract: | Dynamical friction leads to an orbital decay of massive objects like young compact star clusters or Super Massive Black Holes in central regions of galaxies. The dynamical friction force can be well approximated by Chandrasekhar's standard formula, but recent investigations show, that corrections to the Coulomb logarithm are necessary. We propose to use the local scale length as maximum impact parameter and the orbital velocity of the massive object instead of the velocity dispersion of the background particles as typical encounter speed to determine the lower cutoff for a point like object. For extended objects the half mass radius is a good measure of the minimum impact parameter, which should be substituted by the smoothing length or half the cell size for numerical codes. Here we compare the new Coulomb logarithm with an independent numerical determination for different smoothing lengths and numerical codes. These numerical results are in good agreement with our theoretically demanded values. We also give a generalisation of the orbital evolution with a position dependent Coulomb logarithm in cuspy density profiles. |
| Preprint issued: | April 2003 |
| Remarks: |
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Letzte Änderung/Updated: 02.08.2004