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

DOI: 
10.3847/2041-8213/ac2d9a
Publication date: 
24/10/2021
Main author: 
Cerny, W.
IAA authors: 
Martínez-Delgado, D.
Authors: 
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.;Martínez-Delgado, D.;Martínez-Vázquez, 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.;Adamów, M.;Hernandez-Lang, D.;Kuropatkin, N.;Santana-Silva, L.;Tucker, D. L.;Zenteno, A.;Delve Collaboration
Journal: 
The Astrophysical Journal
Publication type: 
Article
Volume: 
920
Pages: 
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<SUB>V</SUB> = - 4.7 ± 0.2), extended ( ${r}_{1/2}={75}_{-13}^{+16}\,\mathrm{pc}$ ), and elliptical (ϵ = 0.54 ± 0.1) system at a heliocentric distance of ${76.7}_{-6.1}^{+4.0}\,\mathrm{kpc}$ , with a stellar population that is well described by an old, metal-poor isochrone (age of τ ~ 13.0 Gyr and metallicity of [Fe/H] ≲ - 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 $({\mu }_{\alpha }\cos \delta ,{\mu }_{\delta })=(+0.25\pm 0.06,-0.10\pm 0.05)$ mas yr<SUP>-1</SUP> 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.
Database: 
ADS
URL: 
https://ui.adsabs.harvard.edu/#abs/2021ApJ...920L..44C/abstract
ADS Bibcode: 
2021ApJ...920L..44C
Keywords: 
Dwarf galaxies;Horizontal branch stars;416;746;Astrophysics - Astrophysics of Galaxies