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Figures 5 and 6 compare parameter correlations for ellipticals, classical bulges, and pseudobulges. Sérsic parameters of (pseudo)bulges are less accurate than those of Es, because deriving them requires a decomposition of brightness profiles into (pseudo)bulge and disk contributions. We have reduced leverage on bulge parameters, and they are strongly coupled to the disk parameters. Nevertheless, Figures 5 and 6 show that classical bulges are indeed indistinguishable from elliptical galaxies, consistent with our definition. Many pseudobulges are not very different, either; this is one reason why they got confused with bulges. To find the difference between pseudobulges and classical bulges, we need to look beyond fundamental plane parameters and consider properties such as flattening and V / sigma. Nevertheless, in Figures 5 and 6, pseudobulges also show larger scatter than classical bulges, and they have smaller Sérsic indices. Consistent with Courteau et al. (1996), MacArthur, Courteau, & Holtzman (2003), and the Carollo team papers, Fisher & Drory (2007a) find a relatively clean separation between classical bulges with n gtapprox 2 and pseudobulges (mostly) with n ltapprox 2. Note that this conclusion would not be clear if we believed that spheroidals are faint ellipticals. In the above, the bulge-pseudobulge distinction is based on morphological criteria listed in KK04 and not on profile shape. We do not understand galaxy formation well enough to predict n for either type of bulge, but the distinction is clearcut enough to be a classification aid.

Figure 6 shows that pseudobulges fade out by becoming low in density, not by becoming compact, like nuclear star clusters (black filled circles). This suggests that pseudobulges and nuclei are fundamentally different.