Constraining Galaxy Evolution With Bulge-Disk-Bar Decomposition

TL;DR

This paper presents a method for detailed three-component galaxy decomposition into bulge, disk, and bar using near-infrared images, revealing that including bars significantly impacts galaxy classification and understanding of galaxy structure.

Contribution

It introduces a three-component decomposition approach with GALFIT, demonstrating the importance of including bars to accurately measure galaxy structures and classifications.

Findings

Including bars reduces bulge-to-total luminosity ratios significantly.

Three-component fits can change galaxy Hubble types from early to late.

Early results show the method's effectiveness across different galaxy environments.

Abstract

Structural decomposition of galaxies into bulge, disk, and bar components is important to address a number of scientific problems. Measuring bulge, disk, and bar structural parameters will set constraints on the violent and secular processes of galaxy assembly and recurrent bar formation and dissolution models. It can also help to quantify the fraction and properties of bulgeless galaxies (those systems having no bulge or only a relatively insignificant disky-pseudobulges), which defy galaxy formation paradigms requiring almost every disk galaxy to have a classical bulge at its core. We demonstrate a proof of concept and show early results of our ongoing three-component bulge-disk-bar decomposition of NIR images for a sample of three complementary samples spanning different epochs and different environments (field and cluster). In contrast to most early studies, which only attempt two-component bulge-disk decomposition, we fit three components using GALFIT: a bulge, a disk, and a bar. We show that it is important to include the bar component, as this can significantly lower the bulge-to-total luminosity ratio (B/T), in many cases by a factor of two or more, thus effectively changing the Hubble type of a galaxy from early to late.