Astrophysically Motivated Bulge-Disk Decompositions of SDSS Galaxies

TL;DR

This study provides detailed bulge-disk decompositions for over 70,000 SDSS galaxies, analyzing their structural components, colors, and classifications to improve understanding of galaxy morphology and evolution.

Contribution

It introduces a large, robust set of bulge-disk decompositions with physical classifications, comparing different fitting methods and analyzing galaxy properties across the color spectrum.

Findings

Only 30% of galaxies have both components significantly detected.

Petrosian concentration correlates well with bulge-to-total ratio.

Most green valley galaxies are bulge+disk systems.

Abstract

We present a set of bulge-disk decompositions for a sample of 71,825 SDSS main-sample galaxies in the redshift range 0.003<z<0.05. We have fit each galaxy with either a de Vaucouleurs ('classical') or an exponential ('pseudo-') bulge and an exponential disk. Two dimensional Sersic fits are performed when the 2-component fits are not statistically significant or when the fits are poor, even in the presence of high signal-to-noise. We study the robustness of our 2-component fits by studying a bright subsample of galaxies and we study the systematics of these fits with decreasing resolution and S/N. Only 30% of our sample have been fit with two-component fits in which both components are non-zero. The g-r and g-i colours of each component for the two-component models are determined using linear templates derived from the r-band model. We attempt a physical classification of types of fits into disk galaxies, pseudo-bulges, classical bulges, and ellipticals. Our classification of galaxies agrees well with previous large B+D decomposed samples. Using our galaxy classifications, we find that Petrosian concentration is a good indicator of B/T, while overall Sersic index is not. Additionally, we find that the majority of green valley galaxies are bulge+disk galaxies. Furthermore, in the transition from green to red B+D galaxies, the total galaxy colour is most strongly correlated with the disk colour.