Dynamical friction and MOND Fernando J Selman DM
- Slides: 8
Dynamical friction and MOND Fernando J. Selman DM vs Alternative Gravities, Edinburgh 22 April 2006 1
The roads to dynamical friction DM vs Alternative Gravities, Edinburgh § Binary collision approximation § Chandrasekhar 1942, 1943 § Chandrasekhar fluctuating force arguments § Uhlenbeck and Ornstein 1930 (non stellar) § Chandrasekhar and von Neumann 1943 § Ahmad and Cohen (1974) § Kandrup (1980) § Bekenstein and Maoz (1992) § del Popolo (1996) o Colpi and Pallavicini (1998) o Nelson and Tremaine (1999) § Polarization cloud method o Marochnik (1968) o Kalnajs (1972) o Lynden-Bell and Kalnajs (1972) o Tremaine and Weinberg (1984) o Bekenstein and Zamir (1990) 22 April 2006 2
The approximations § § Binary collisions Local approximation: infinite and homogeneous system Markov approximation: binary collisions of negligible duration Diffusion approximation: diffusion described by a Fokker-Planck equation § Neglect of self-gravity of response § Resonances DM vs Alternative Gravities, Edinburgh 22 April 2006 3
Chandrasekhar Binary Collisions Formula DM vs Alternative Gravities, Edinburgh 22 April 2006 4
Statistics of the fluctuating field DM vs Alternative Gravities, Edinburgh 22 April 2006 5
Polarization cloud method DM vs Alternative Gravities, Edinburgh 22 April 2006 6
The frictional drag formulas DM vs Alternative Gravities, Edinburgh 22 April 2006 7
Caveat: M=10^5 Msun, V = 100 km/s, 20 pc x 30 pc DM vs Alternative Gravities, Edinburgh 22 April 2006 8