Description
We present two new nonparametric methods for quantifying galaxy morphology: the relative distribution of the galaxy pixel flux values (the Gini coefficient or G) and the second-order moment of the brightest 20% of the galaxy's flux (M_20_). We test the robustness of G and M_20_ to decreasing signal-to-noise ratio (S/N) and spatial resolution and find that both measures are reliable to within 10% for images with average S/N per pixel greater than 2 and resolutions better than 1000 and 500pc, respectively. We have measured G and M_20_, as well as concentration (C), asymmetry (A), and clumpiness (S) in the rest-frame near-ultraviolet/optical wavelengths for 148 bright local "normal" Hubble-type galaxies (E-Sd) galaxies, 22 dwarf irregulars, and 73 0.05<z<0.25 ultraluminous infrared galaxies (ULIRGs).
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