On the Formation of Elliptical Galaxies

Simple collapse and violent relaxation models produce sharply cut off envelopes with p(r) oc , whereas actual elliptical galaxies have more extended envelopes approximately given by p(r) oc r -3 as implied by Hubble's law. Numerical models are presented, showing that when cosmological infall effects are included, galaxies are produced with envelopes having a p(r) oc r -2.8 dependence in excellent agreement with Hubble's law. We have also computed a realistic rotating model of an ES galaxy which includes infall effects and where the angular momentum of the galaxy is gained through tidal interactions with neighboring protogalaxies. The envelope displays a Hubble dependence but at great distances shows a cutoff due to the tidal effects. The model gives an outstandingly good fit to the envelope of the ES galaxy NGC 4697. Except for simple scaling, this fit is produced without the use of any free-fitting parameters. A mass-to-light ratio for NGC 4697 is also computed. Subject headings: galaxies - galaxies, motions in - stellar dynamics