What Is a Pseudobulge, and Why Should I Care?
David Fisher (Swinburne Institute of Technology)
Observations show that bulges come in at least two different types: pseudobulges, which have properties similar to disks, and classical bulges, which have properties similar to elliptical galaxies. I will show that these pseudobulges are gas rich, star forming, dynamically cold, and do not participate in the fundamental plane. These properties are more consistent with a formation scenario in which pseudobulges are the result of secular processes, such as bar driven evolution. Indeed, I will show connections between pseudobulge properties and bars, which are consistent with a picture in which bars preferentially build pseudobulges. The data is consistent with a scenario in which the two types of bulges are indicative of different channels of galaxy evolution. Pseudobulges imply a merger-quiet history, and the consistency between classical bulges and elliptical galaxies suggest that classical bulges may have experienced more merging at low redsh ift. Finally, I will show that in the local Universe 75% of bulge-disk galaxies contain pseudobulges. This implies first that theories aimed at describing the evolution of galaxies must account for the properties of galaxies, and secondly that large surveys, such as the Galaxy Zoo, are filled with galaxies containing pseudobulges.