Eridanus IV: an Ultra-faint Dwarf Galaxy Candidate Discovered in the DECam Local Volume Exploration Survey

Cerny, W.; Pace, A. B.; Drlica-Wagner, A.; Koposov, S. E.; Vivas, A. K.; Mau, S.; Riley, A. H.; Bom, C. R.; Carlin, J. L.; Choi, Y.; Erkal, D.; Ferguson, P. S.; James, D. J.; Li, T. S.; Martinez-Delgado, D.; Martinez-Vazquez, C. E.; Munoz, R. R.; Mutlu-Pakdil, B.; Olsen, K. A. G.; Pieres, A.; Sakowska, J. D.; Sand, D. J.; Simon, J. D.; Smercina, A.; Stringfellow, G. S.; Tollerud, E. J.; Adamow, M.; Hernandez-Lang, D.; Kuropatkin, N.; Santana-Silva, L.; Tucker, D. L. and Zenteno, A. (2021): Eridanus IV: an Ultra-faint Dwarf Galaxy Candidate Discovered in the DECam Local Volume Exploration Survey. In: Astrophysical Journal Letters, Vol. 920, No. 2, L44

Abstract

We present the discovery of a candidate ultra-faint Milky-Way satellite, Eridanus IV (DELVE J0505-0931), detected in photometric data from the DECam Local Volume Exploration survey (DELVE). Eridanus IV is a faint (M-V = - 4.7 +/- 0.2), extended (r(1/2)=75(-13)(+16) pc ), and elliptical (epsilon = 0.54 +/- 0.1) system at a heliocentric distance of 76.7(-6.1)(+4.0)kpc, with a stellar population that is well described by an old, metal-poor isochrone (age of tau similar to 13.0 Gyr and metallicity of [Fe/H] less than or similar to - 2.1 dex). These properties are consistent with the known population of ultra-faint Milky-Way satellite galaxies. Eridanus IV is also prominently detected using proper-motion measurements from Gaia Early Data Release 3, with a systemic proper motion of (mu(alpha) cos delta,mu(delta))=(+0.25 +/- 0.06,-0.10 +/- 0.05) mas yr(-1) measured from its horizontal branch and red-giant-branch member stars. We find that the spatial distribution of likely member stars hints at the possibility that the system is undergoing tidal disruption.

• Item Type: Journal article
• Faculties: Physics
• Subjects: 500 Science > 530 Physics
• ISSN: 2041-8205
• Language: English