We present a catalog of 20,977 extended low-surface-brightness galaxies ( LSBGs ) identified in { \sim } 5000 \deg ^ { 2 } from the first three years of imaging data from the Dark Energy Survey ( DES ) .
Based on a single-component Sérsic model fit , we define extended LSBGs as galaxies with g -band effective radii R _ { eff } ( g ) > 2.5 ^ { \prime \prime } and mean surface brightness \bar { \mu } _ { eff } ( g ) > 24.3 \mathrm { mag } \mathrm { arcsec ^ { -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 0.59 ) and blue ( g - i < 0.59 ) galaxies and study the properties of the two populations .
Redder LSBGs are more clustered than their blue counterparts , and are correlated with the distribution of nearby ( z < 0.10 ) bright galaxies .
Red LSBGs constitute \sim 35 \% of our LSBG sample , and { \sim } 30 \% of these are located within 1 deg of low-redshift galaxy groups and clusters ( compared to \sim 8 \% of the blue LSBGs ) .
For nine of the most prominent galaxy groups and clusters , we calculate the physical properties of associated LSBGs assuming a redshift derived from the host system .
In these systems , we identify 108 objects that can be classified as ultra-diffuse galaxies , defined as LSBGs with projected physical effective radii R _ { eff } > 1.5 \mathrm { kpc } .
The wide-area sample of LSBGs in DES can be used to test the role of environment on models of LSBG formation and evolution .