Morphological Classification of Luminous Infrared Galaxies in GOALS

Luminous Infrared Galaxies (LIRGs) are massive starbursts, typically composed of two or more galaxies at some stage of a galaxy merger. LIRGs dominate the infrared luminosity density at high redshift, so studying nearby LIRGs can give us insight into galaxies at high redshift. We analyze HST ACS/WFC images of a sample of 56 LIRGs by computing their Gini coefficient and M_20 value at F435W (B-band) and F814W (I-band), and we use these results to classify the galaxies as mergers or non-mergers. We present the results of this analysis, and then sort the galaxies by a variety of parameters to identify trends in the data. Additionally, we analyzed the individual components of widely separated galaxies, expanding our sample to 85 individual components, and we note differences in trends compared to widely separated systems that were analyzed using images that contained both components. We find that the I-band is a better metric for classifying LIRGs as mergers via Gini-M_20 analysis, and that very early and very late stage mergers are often classified as non-mergers. Based on our analysis, Gini-M_20 merger classifications of high-redshift galaxies may be challenging for widely separated pairs and will be less accurate for rest-frame 0.4 µm images.