One of the science applications of GALFIT is to fit big nearby galaxies, to probe the detailed structures of galaxies. Even though many big galaxies look smooth and featuresless to the eye, when one removes the bright features, residuals may remain that reveal evidence of fine structures, like shells, double nuclei, dust, nuclear rings, stellar nuclei, etc.. These structures may indicate past episodes of galaxy mergers and interactions, or faint emissions coming from around supermassive black holes.

The following images came from work done on nearby galaxies and published in Peng, Ho, Impey, & Rix (2002, AJ, 124, 266). The original data were obtained using the Wide Field and Planetary Camera 2 (WFPC2) onboard the Hubble Space Telescope (HST). The images below show the entire PC chip, or about 800×800 pixels. The number and type of components used vary from galaxy to galaxy depending on how complicated they are.

Left = original data, Middle = model fit, Right = residual image.

That's all for now. One can find many more examples in Peng, Ho, Impey, & Rix (2002, AJ, 124, 266), from which most of these images were taken.

Go back to GALFIT Home Page.
Go back to Chien Peng's Home Page.

Chien Peng ()