Dissipation in Galaxy Formation
Astronomy 626: Spring 1995
Cooling Times and Galactic Scales
Only those systems with t_cool < t_dyn can become
galaxies before being incorporated into larger structures.
Core Condensation in Heavy Halos
Clustering of dark matter provides potential wells in which
luminous galaxies form. The latter survive the merging of their halos
because dissipation has increased their binding energies.
Rotation of Disk Galaxies
Torques between objects impart a modest amount of angular
momentum. A self-gravitating cloud must then collapse by a large
factor to reach centrifugal equilibrium, while the collapse factors
for clouds in heavy halos are more reasonable.
- The cooling catastrophe: rapid cooling in small halos
could turn all gas into stars before large galaxies can form.
- In hierarchical pictures, the brighter objects are typically
younger, and we would expect them to be bluer as well.
- The predicted luminosity function has too many faint galaxies.
- Binney, J. 1977, Ap.J. 215, 483.
- Fall, S.M. & Efstathiou, G.P.E. 1980, M.N.R.A.S.
- Rees, M.J. & Ostriker, J.P. 1977, M.N.R.A.S.
- Silk, J. 1977, Ap.J. 211, 638.
- White, S.D.M. & Rees, M.J. 1978, M.N.R.A.S.
Joshua E. Barnes
Last modified: April 10, 1995