Tidal Debris and Galaxy Recycling

Tidal Dwarfs

Dynamical mechanism:
    • Instabilities in stellar disks lead to collapse and formation of bound structures (Barnes and Hernquist 1992)
    • Fragmentation of gas in tidal tails (Elmegreen etal 1993)
(from Hibbard etal 1994)
Expected Properties of Tidal Dwarfs:
  • Moderately low metallicity
  • Dark matter poor
  • Mix of stellar populations
  • Loosely bound to remnant/parent galaxy




Dynamics of NGC 7252 star forming lumps (Hibbard & Mihos 1995):

Disk Rebuilding in Early Type Galaxies

Violent relaxation destroys old stellar disks in a merger. How can disks be rebuilt?
  • Cooling of hot gas into potential well (eg SAMs, Steinmetz and Navarro 2002).
  • Return of tidally expelled gas (Mihos & Hernquist 1996; Barnes  2002; Naab etal 2003)
    • HI disks, rings in ellipticals (eg van Gorkum etal)
    • Disks in ellipticals (eg Bender etal, Burstein etal)
    • Rebuilding high B/D systems? (Schweizer 1996, Bekki 1998)
 





Nearby likely example of tidal reaccretion:

Centaurus A (NGC 5128)
(Malin etal 1983; Schminovich etal 1994)