We present a catalog of 23,790 extended low-surface-brightness galaxies (LSBGs) identified in ~5000 deg2 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 Reff (g) > 2."5 and mean surface brightness μeff (g )> 24.2 mag arcsec-2. We find that the distribution of LSBGs is strongly bimodal in (g-r) versus (g-i) color space. We divide our sample into red (g-i ≥ 0.60) and blue (g-i < 0.60) 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 (< 0.10) bright galaxies. Red LSBGs constitute ~33% of our LSBG sample, and ~30% of these are located within 1° of low-redshift galaxy groups and clusters (compared to ~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 41 objects that can be classified as ultradiffuse galaxies, defined as LSBGs with projected physical effective radii Reff > 1.5 kpc and central surface brightness μ0 (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.

Original languageEnglish
Number of pages26
JournalAstrophysical Journal, Supplement Series
Issue number2
Publication statusPublished - 25 Jan 2021


  • UKRI
  • STFC


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