Density profiles of galaxy bulges and nuclei

The bulge contribution to the inner density profile of a galaxy is well traced by the bulge's NIR surface brightness profile. We map the surface brightness profiles of bulges using HST/NICMOS imaging. Most bulges show nuclear components of 20-200 pc scales, and frequently also unresolved nuclear star clusters (<20 pc). These nuclear components are the densest parts of bulges, and gave bulges the 'reputation' of having high stellar concentration. Actually, the Sérsic r1/n bulges typically have low concentrations, 1