~ a few % of luminous galaxies in the NGC catalog are strongly interacting.
Toomre 1977: extrapolating merger rate back in time gives ~ 700 remnants, similar to the number of NGC ellipticals.
the merger hypothesis
| In the local universe, many galaxies have close
companions or show evidence of a major, recent encounter.
~ a few % of luminous galaxies in the NGC catalog are strongly interacting. Toomre 1977: extrapolating merger rate back in time gives ~ 700 remnants, similar to the number of NGC ellipticals. the merger hypothesis |
|
| These interactions are effective at compressing the galaxies' ISM and driving strong bursts of star formation... |  |
|
...which rival quasars as the most luminous objects in
the universe (L ~ 1012 Lsun).
These ultraluminous infrared galaxies are starbursts triggered by massive quantities of gas (Mgas ~ 1010 Msun) being driven into the nuclear regions of the galaxies during the final stages of the mergers. |
| When the merger is complete, the starburst dies
down, and we are left with an elliptical like remnant with strong tidal
features.
NGC 7252 |
|
