\,
\mathrm{pc}$. Cores are not the only characteristic by which the most massive and brightest ellipticals are distinct from fainter elliptical galaxies: massive ellipticals are less flattened, with boxy instead of disky isophotes, and are dominated by unordered, rather than rotational, stellar motions [e.g. @Kormendy96; @Faber97]. Based on statistical comparisons between observed galaxies and numerical $N$-body simulations these morphological differences provide circumstantial evidence for two distinct formation paths. Fainter ellipticals likely form from mergers of disk-dominated progenitor galaxies that are rich in gas; the gas can then settle into a rotational, disky configuration before forming new stars. The most massive ellipticals, however, are thought to form through gas-poor (i.e., elliptical-elliptical) mergers.

The existence of cores represents a challenge to our understanding of the merging process. The central structure of a merger without gas is dominated by the more concentrated of the two progenitors: the steeper central density cusp survives [@Fulton01; @Boylan-Kolchin04]. Since high-mass ellipticals are thought to be built from mergers of lower-mass ellipticals, which have steep central-density cusps, the shallower cores in more massive ellipticals have to be the result of another physical mechanism. Supermassive black holes (SMBHs) that reside in the centers of essentially all elliptical galaxies provide 