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A New Approach to Galaxy Morphology: I. Analysis of the Sloan Digital Sky Survey Early Data Release

By SpaceRef Editor
January 15, 2003
Filed under , ,

Astrophysics, abstract
astro-ph/0301239


From: Roberto Abraham <[email protected]>
Date: Tue, 14 Jan 2003 05:26:11 GMT (465kb)

A New Approach to Galaxy Morphology: I. Analysis of the Sloan Digital
Sky Survey Early Data Release


Authors:
Roberto Abraham (1),
Sidney van den Bergh (2),
Preethi Nair (1) ((1) Dept. of Astronomy & Astrophysics, University of Toronto, (2) Herzberg Institute of Astrophysics, National Research Council of Canada)

Comments: ApJ in press


In this paper we present a new statistic for quantifying galaxy morphology
based on measurements of the Gini coefficient of galaxy light distributions.
This statistic is easy to measure and is commonly used in econometrics to
measure how wealth is distributed in human populations. When applied to galaxy
images, the Gini coefficient provides a quantitative measure of the inequality
with which a galaxy’s light is distributed amongst its constituent pixels. We
measure the Gini coefficient of local galaxies in the Early Data Release of the
Sloan Digital Sky Survey and demonstrate that this quantity is closely
correlated with measurements of central concentration, but with significant
scatter. This scatter is almost entirely due to variations in the mean surface
brightness of galaxies. By exploring the distribution of galaxies in the
three-dimensional parameter space defined by the Gini coefficient, central
concentration, and mean surface brightness, we show that all nearby galaxies
lie on a well-defined two-dimensional surface (a slightly warped plane)
embedded within a three-dimensional parameter space. By associating each galaxy
sample with the equation of this plane, we can encode the morphological
composition of the entire SDSS g-band sample using the following three numbers:
22.451, 5.366, 7.010. The i-band sample is encoded as: 22.149, 5.373, and
7.627.

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