Determining the Accuracy of GALFIT in Morphology Measurement of Galaxies from Image Analysis

Wan Hang (Vincent) Hui


In this experiment, a program called GALFIT was used to generate realistic models of galaxies. By inputting parameters such as magnitude, effective radius and the Sérsic index, it used the Sérsic profile to generate a light profile for the galaxies. Then each model was stacked onto an image from the Hubble Space Telescope. Then GALFIT was used to extract information of those models from the image, and the information was compared to the original input data. We have accurate measurements for the magnitude and the effective radius of the elliptical galaxies, and the measurement for the Sérsic index had more errors in comparison. Then, we had difficulties in using GALFIT for bulge-disk decomposition of the disk galaxies. We found that although it identified those disk galaxies as a whole, it failed to separate the two components and the measurements had large errors.