Tidal Debris in Elliptical Galaxies as Tracers of Mergers with Disks

摘要: We use a set of high-resolution N-body simulations binary galaxy mergers to show that the morphologies tidal features are seen around large fraction nearby, massive ellipticals in field cannot be reproduced by equal-mass dissipationless mergers; rather, they well explained accretion disk-dominated galaxies. In particular, arm- and looplike observed debris can only produced kinematically cold material disk components accreted The arise from such "cold-accretion" events onto elliptical visible for significantly longer timescales than elliptical-elliptical (about 1-2 Gyr vs. few hundred million years). Mass ratios order 1:10 between accreting sufficient match brightness debris. Furthermore, stellar population synthesis models simple order-of-magnitude calculations indicate colors generated minor cold-accretion relatively red, agreement with observations. explain presence, brightness, structural color properties cause modest mass luminosity increase elliptical. These results, coupled relative statistical frequencies disk- bulge-dominated galaxies field, suggest assemble most their before forms through little, rather very recent, major mergers.