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Galaxy evolution. Isolated compact elliptical galaxies: stellar systems that ran away
Igor Chilingarian1, Ivan Zolotukhin2
1Smithsonian Astrophysical Observatory, 60 Garden Street MS09, Cambridge, MA 02138, USA. Sternberg Astronomical Institute, Moscow State University, 13 Universitetsky prospect, Moscow 119992, Russia. igor.chilingarian@cfa.harvard.edu.
Abstract:
Compact elliptical galaxies form a rare class of stellar system (~30 presently known) characterized by high stellar densities and small sizes and often harboring metal-rich stars. They were thought to form through tidal stripping of massive progenitors, until two isolated objects were discovered where massive galaxies performing the stripping could not be identified. By mining astronomical survey data, we have now found 195 compact elliptical galaxies in all types of environment. They all share similar dynamical and stellar population properties. Dynamical analysis for nonisolated galaxies demonstrates the feasibility of their ejection from host clusters and groups by three-body encounters, which is in agreement with numerical simulations. Hence, isolated compact elliptical and isolated quiescent dwarf galaxies are tidally stripped systems that ran away from their hosts.
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