Bulges Of Nearby Galaxies With Spitzer: Scaling Relations in
  Pseudobulges and Classical Bulges
  We investigate scaling relations of bulges using bulge-disk decompositions at
3.6 micron and present bulge classifications for 173 E-Sd galaxies within 20
Mpc. Pseudobulges and classical bulges are identified using Sersic index, HST
morphology, and star formation activity (traced by 8 micron emission). In the
near-IR pseudobulges have n_b<2 and classical bulges have n_b>2, as found in
the optical. Sersic index and morphology are essentially equivalent properties
for bulge classification purposes. We confirm, using a much more robust sample,
that the Sersic index of pseudobulges is uncorrelated with other bulge
structural properties, unlike for classical bulges and elliptical galaxies.
Also, the half-light radius of pseudobulges is not correlated with any other
bulge property. We also find a new correlation between surface brightness and
pseudobulge luminosity; pseudobulges become more luminous as they become more
dense. Classical bulges follow the well known scaling relations between surface
brightness, luminosity and half-light radius that are established by elliptical
galaxies. We show that those pseudobulges (as indicated by Sersic index and
nuclear morphology) that have low specific star formation rates are very
similar to models of galaxies in which both a pseudobulge and classical bulge
exist. Therefore, pseudobulge identification that relies only on structural
indicators is incomplete. Our results, especially those on scaling relations,
imply that pseudobulges are very different types of objects than elliptical
galaxies.
