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This paper studies pseudo-bulges (P-bulges) and classical bulges (C-bulges)in Sloan Digital Sky Survey central galaxies using the new bulge indicator$\Delta\Sigma_1$, which measures relative central stellar-mass surface densitywithin 1 kpc. We compare $\Delta\Sigma_1$ to the established bulge-typeindicator $\Delta\langle\mu_e\rangle$ from Gadotti (2009) and show thatclassifying by $\Delta\Sigma_1$ agrees well with $\Delta\langle\mu_e\rangle$.$\Delta\Sigma_1$ requires no bulge-disk decomposition and can be measured onSDSS images out to $z = 0.07$. Bulge types using it are mapped onto twentydifferent structural and stellar-population properties for 12,000 SDSS centralgalaxies with masses 10.0 < log $M_*$/$M_{\odot}$ < 10.4. New trends emergefrom this large sample. Structural parameters show fairly linear log-logrelations vs. $\Delta\Sigma_1$ and $\Delta\langle\mu_e\rangle$ with onlymoderate scatter, while stellar-population parameters show a highly non-linear"elbow" in which specific star-formation rate remains roughly flat withincreasing central density and then falls rapidly at the elbow, where galaxiesbegin to quench. P-bulges occupy the low-density end of the horizontal arm ofthe elbow and are universally star-forming, while C-bulges occupy the elbow andthe vertical branch and exhibit a wide range of star-formation rates at fixeddensity. The non-linear relation between central density and star-formationrate has been seen before, but this mapping onto bulge class is new. The widerange of star-formation rates in C-bulges helps to explain why bulgeclassifications using different parameters have sometimes disagreed in thepast. The elbow-shaped relation between density and stellar indices suggeststhat central structure and stellar-populations evolve at different rates asgalaxies begin to quench.

Structural and Stellar Population Properties vs. Bulge Types in Sloan Digital Sky Survey Central Galaxies