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2015ApJ...807...56B - Astrophys. J., 807, 56 (2015/July-1)
Structure and formation of cD galaxies: NGC 6166 in Abell 2199.
BENDER R., KORMENDY J., CORNELL M.E. and FISHER D.B.
Abstract (from CDS):
However, our photometry does not confirm the widespread view that cD halos are identifiable as an extra, low-surface-brightness component that is photometrically distinct from the inner, steep-Sérsic-function main body of an otherwise-normal giant elliptical galaxy. Instead, all of the brightness profile of NGC 6166 outside its core is described to ±0.037 V mag/arcsec2 by a single Sérsic function with index. The cD halo is not recognizable from photometry alone. This blurs the distinction between cluster-dominated cD halos and the similarly-large-Sérsic-index halos of giant, core-boxy-nonrotating ellipticals. These halos are believed to be accreted onto compact, high-redshift progenitors (''red nuggets'') by large numbers of minor mergers. They belong dynamically to their central galaxies. Still, cDs and core-boxy-nonrotating Es may be more similar than we think: both may have outer halos made largely via minor mergers and the accumulation of tidal debris.
We construct a main-body+cD-halo decomposition that fits both the brightness and dispersion profiles. To fit, we need to force the component Sérsic indices to be smaller than a minimum- photometric decomposition would suggest. The main body has of the total galaxy light. The cD halo has, ∼1/2 mag brighter than the brightest galaxy in the Virgo cluster. A mass model based on published cluster dynamics and X-ray observations fits our observations if the tangential dispersion is larger than the radial dispersion at -. The cD halo is as enhanced in α element abundances as the main body of NGC 6166. Quenching of star formation in ≲1 Gyr suggests that the center of Abell 2199 has been special for a long time during which dynamical evolution has liberated a large mass of now-intracluster stars.
Abstract Copyright: ∼
Journal keyword(s): galaxies: elliptical and lenticular, cD - galaxies: evolution - galaxies: formation - galaxies: kinematics and dynamics - galaxies: photometry - galaxies: structure
Simbad objects: 19
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