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

D. Tanoglidis, A. Drlica-Wagner, K. Wei, T. S. Li, F. J. Sánchez, Y. Zhang, A. H. G. Peter, A. Feldmeier-Krause, J. Prat, K. Casey, A. Palmese, C. Sánchez, J. DeRose, C. Conselice, T. M. C. Abbott, M. Aguena, S. Allam, S. Avila, K. Bechtol, E. Bertin, S. Bhargava, D. Brooks, D. L. Burke, A. Carnero Rosell, M. Carrasco Kind, J. Carretero, C. Chang, M. Costanzi, L. N. da Costa, J. De Vicente, S. Desai, H. T. Diehl, P. Doel, T. F. Eifler, S. Everett, A. E. Evrard, B. Flaugher, J. Frieman, J. García-Bellido, D. W. Gerdes, R. A. Gruendl, J. Gschwend, G. Gutierrez, W. G. Hartley, D. L. Hollowood, D. Huterer, D. J. James, E. Krause, K. Kuehn, N. Kuropatkin, M. A. G. Maia, M. March, J. L. Marshall, F. Menanteau, R. Miquel, R. L. C. Ogando, F. Paz-Chinchón, A. K. Romer, A. Roodman, E. Sanchez, V. Scarpine, S. Serrano, I. Sevilla-Noarbe, M. Smith, E. Suchyta, G. Tarle, D. Thomas, D. L. Tucker, A. R. Walker

Published 2020-06-08Version 1

We present a catalog of 20,977 extended low-surface-brightness galaxies (LSBGs) identified in ~ 5000 deg$^2$ from the first three years of imaging data from the Dark Energy Survey (DES). Based on a single-component S\'ersic model fit, we define extended LSBGs as galaxies with $g$-band effective radii $R_{\scriptsize{eff}} > 2.5"$ and mean surface brightness $\bar{\mu}_{\scriptsize{eff}}(g) > 24.3$ mag 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 $R_{\scriptsize{eff}} > 1.5$ 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.