Astronomy Tea Talk

The division of galaxies into disk and spheroid components is very old and reasonably successful. I will discuss a new set of two-dimensional bulge-disk(B+D) decompositions for 70,000 nearby Sloan Digital Sky Survey (SDSS) galaxies, the largest such set to date. Each galaxy is fit with five different 2-dimensional models and the best fitting model is selected based on chi-squared values and astrophysical constraints (color, bulge-to-total ratio, shape, etc.). Fifty percent of the galaxies cannot be fit with a B+D model, but this represents only 20% of the stellar mass in our sample. Bulge color and shape can be used to separate elliptical-like classical bulges from disk-like pseudo-bulges and this method agrees reasonably well with other methods used to distinguish classical bulges from pseudo-bulges. This large data set can be used to study the properties of different morphological types over a large range of galaxy properties and environments.