We present a structural analysis of 138 compact elliptical galaxies (cEs) in the redshift range of z < 0. 05 using the Sloan Digital Sky Survey (SDSS) DR12 data. We perform single- and double-component Sérsic model fitting to their SDSS r-band surface brightness profiles. By dividing cEs into those with cE (w) and without cE (w/o) a bright host galaxy, we find a significant structural dichotomy: the majority (85\%) of cE (w) s exhibit single-component profiles, while a similar proportion (85\%) of isolated cE (w/o) s display double-component profiles, characterized by a compact, inner component and a diffuse, disk-like outer component. These results suggest that host-associated cE (w) s primarily form through the tidal stripping of larger progenitors, resulting in a compact bulge-like core. In contrast, isolated cE (w/o) s appear to form intrinsically at early epochs, likely through gas-rich mergers, and retain disk-like outer structures. The Sérsic index distribution of cE (w) s with single-component structure indicates progenitor types ranging from pseudo-bulge to classical bulge, supported by differences in stellar populations. A small fraction of cEs, including double-component cE (w) s and single-component cE (w/o) s, suggests complex evolutionary channels involving environmental capture or ejection. Our results emphasize that the structural characteristics of cEs, specifically the presence or absence of an extended outer envelope, serve as a crucial diagnostic tool to distinguish tidally stripped remnants from intrinsically formed low-mass cEs in isolation.
Yi et al. (Mon,) studied this question.