Separating Galaxies in Color-Magnitude Space
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Date
2023-05
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The Ohio State University
Abstract
In this study, bright galaxies in the redshift range 0.004 < z < 0.4 are studied to understand the evolution of galaxy color as a function of redshift. Galaxy color is a diagnostic mechanism for detecting the amount of star formation in galaxies. This galaxy sample is drawn from the Bright Galaxy Survey, completed using the Dark Energy Spectroscopic Instrument. The light selected in this paper consists of the u (ultra-violet) band and the r (red) band. For galaxies of a given absolute magnitude, the distribution of color is frequently bimodal; therefore, we fit the color distribution using a double Gaussian function. Over the entire range of redshift examined, the color–magnitude distribution is well-fitted by a broad blue sequence from 0.7 +/- 0.27 u-r, and a narrower red sequence from 2.2 +/- 0.13 u-r. The optimal divider between the red and blue sequences is seen to be ~ 0.1 magnitudes redder at higher redshift (z > 0.2) than at lower redshift (z < 0.2). This shift in divider is due primarily to the blue population increasing with redshift, meaning the blue population is moving blueward.
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Keywords
Galaxy morphology, Galactic evolution