Integrated Galaxy Light from Stacking 10⁵ Random Pointings in the Dark Energy Survey Data

Abstract We present a new technique for measuring the integrated galaxy light (IGL) with stacked image data from the Dark Energy Survey (DES). We extract 1′ × 1′ cutouts from nearly 100,000 randomly selected positions in the g, r, i, z, and Y bands from the DES Data Release 2 maps. We generate source catalogs and masks for each cutout, and the images are subsequently stacked to generate deep images of the sky both with and without sources. The IGL is then calculated by taking the difference in average brightness between stacks that contain galaxies and stacks in which galaxies have been masked. We find IGL values of g = 4.27 ± 0.28, r = 6.97 ± 0.42, i = 8.66 ± 0.53, z = 10.16 ± 0.7, and Y = 13.78 ± 2.35 nW m −2 sr −1 . These measurements, which require no foreground estimation or removal, are in agreement with previously reported IGL values derived from galaxy number counts and other methods. This stacking technique reduces the sensitivity to diffuse local backgrounds but is not sensitive to large-scale diffuse extragalactic background light.