Shadows in the Dark: Low-Surface-Brightness Galaxies Discovered in the Dark Energy Survey

We present a catalog of 23,790 extended low-surface-brightness galaxies (LSBGs) identified in $\sim 5000 ��^2$ from the first three years of imaging data from the Dark Energy Survey (DES). Based on a single-component S��rsic model fit, we define extended LSBGs as galaxies with $g$-band effective radii $R_{eff}(g) > 2.5''$ and mean surface brightness $\bar��_{eff}(g) > 24.2 \,mag ��rcsec^{-2}$. We find that the distribution of LSBGs is strongly bimodal in $(g-r)$ vs.\ $(g-i$) color space. We divide our sample into red ($g-i \geq 0.60$) and blue ($g-i 1.5 \,kpc$ and central surface brighthness $��_0(g) > 24.0\, mag \,arcsec^{-2}$. The wide-area sample of LSBGs in DES can be used to test the role of environment on models of LSBG formation and evolution.
31 pages, 19 figures. Version accepted for publication in ApJS. Data products related to this work can be found in: https://des.ncsa.illinois.edu/releases/other/y3-lsbg