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For refcode 1991A&A...244L..25N:
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Copyright by European Southern Observatory (ESO). Reproduced by permission
1991A&A...244L..25N Letter to the Editor The shape of central regions in elliptical galaxies J.-L. Nieto, R. Bender, J. Arnaud, and P. Surma Observatoire Midi-Pyrenees, Unite Associee au CNRS no. 285,14 Avenue Edouard Belin, F-31400 Toulouse Canada-France-Hawaii Telescope Corporation, P.O. Box 1597, Kamuela, HI 96743, USA Landessternwarte, Konigstuhl, W-6900 Heidelberg, Federal Republic of Germany Department of Physics, Oxford University, Keble Road, Oxford OXI 3RH, England Received January 3, accepted February 21, 1991 Abstract. Isophote analysis of high-resolution CCD images of a large sample of 75 early-type, mostly elliptical, galaxies shows that at least 1/3 (= 25) of these objects harbors central bodies that appear separate from the rest of the galaxy, and whose sizes range between 2 and 10 arcsec; 15 of these 25 central substructures show clearly `pointed' isophotes, and all objects known to have decoupled core kinematics show a photometric substructure coinciding in radius with the kinematic substructure. About 60% of `resolved' (r_c,app_/{sigma}*=f>5), ~40% of intermediate (5 > f > 3) and ~20% of `unresolved' (f < 3) galaxies contain such separate substructures. The percentage of such phenomena is higher in galaxies with boxy and irregular isophotal shapes (~55%) than in those having disky isophotes (~28%). These numbers suggest that a large fraction of elliptical galaxies, if not all, should be found to contain separate entities in their central regions if investigated with sufficient spatial resolution. The separate entities may be formed in merger events, as it is likely for galaxies with counter-rotating or otherwise kinematically decoupled cores; however, from the large variety of early-type galaxies showing this type of phenomenon, internal mass transfer cannot be excluded. Several arguments suggest that these central substructures are predominantly disks. Key Words: Galaxies: photometry, ellipticals, evolution - Elliptical : structure, central regions
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