Authors: Marc Balcells, Alister W. Graham, Lilian Dominguez-Palmero, Reynier Peletier
Abstract: We have used Hubble Space Telescope (HST) near-infrared imaging to explore the shapes of the surface brightness profiles of bulges in nearby S0-Sbc galaxies. Our modeling extends to the outer bulge via a bulge-disk decomposition of combined HST and ground-based profiles. Compact, central unresolved components similar to those reported by others are found in ~84% of the sample. We also detect a moderate frequency (~34%) of nuclear components having exponential profiles which may be disks or bars. Adopting the Sersic r(1/n) functional form for the bulge, none of the bulges have an r(1/4) behaviour; the average Sersic shape-index is 1.7±0.7. For the same sample, fits to only the NIR ground-based profiles yield Sersic indices reaching values of 4-6. These high-n values are a result of the nuclear components blending with the bulge light due to atmospheric seeing. The lower Sersic indices derived using the HST profiles are not expected from current models of violent relaxation, and argue against significant merger growth for most bulges.