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Mau, S.; Cerny, W.; Pace, A. B.; Choi, Y.; Drlica-Wagner, A.; Santana-Silva, L.; Riley, A. H.; Erkal, D.; Stringfellow, G. S.; Adamów, M.; Carlin, J. L.; Gruendl, R. A.; Hernandez-Lang, D.; Kuropatkin, N.; Li, T. S.; Martínez-Vázquez, C. E.; Morganson, E.; Mutlu-Pakdil, B.; Neilsen, E. H.; Nidever, D. L.; Olsen, K. A. G.; Sand, D. J.; Tollerud, E. J.; Tucker, D. L.; Yanny, B.; Zenteno, A.; Allam, S.; Barkhouse, W. A.; Bechtol, K.; Bell, E. F.; Balaji, P.; Crnojevi, D.; Esteves, J.; Ferguson, P. S.; Gallart, C.; Hughes, A. K.; James, D. J.; Jethwa, P.; Johnson, L. C.; Kuehn, K.; Majewski, S.; Mao, Y.-Y.; Massana, P.; McNanna, M.; Monachesi, A.; Nadler, E. O.; Noël, N. E. D.; Palmese, A.; Paz-Chinchon, F.; Pieres, A.; Sanchez, J.; Shipp, N.; Simon, J. D.; Soares-Santos, M.; Tavangar, K.; van der Marel, R. P.; Vivas, A. K.; Walker, A. R.; Wechsler, R. H.
The Astrophysical journal, 02/2020, Volume: 890, Issue: 2Journal Article
We report the discovery of two ultra-faint stellar systems found in early data from the DECam Local Volume Exploration survey (DELVE). The first system, Centaurus I (DELVE J1238-4054), is identified as a resolved overdensity of old and metal-poor stars with a heliocentric distance of , a half-light radius of , an age of , a metallicity of , and an absolute magnitude of . This characterization is consistent with the population of ultra-faint satellites and confirmation of this system would make Centaurus I one of the brightest recently discovered ultra-faint dwarf galaxies. Centaurus I is detected in Gaia DR2 with a clear and distinct proper motion signal, confirming that it is a real association of stars distinct from the Milky Way foreground; this is further supported by the clustering of blue horizontal branch stars near the centroid of the system. The second system, DELVE 1 (DELVE J1630-0058), is identified as a resolved overdensity of stars with a heliocentric distance of , a half-light radius of , an age of , a metallicity of , and an absolute magnitude of , consistent with the known population of faint halo star clusters. Given the low number of probable member stars at magnitudes accessible with Gaia DR2, a proper motion signal for DELVE 1 is only marginally detected. We compare the spatial position and proper motion of both Centaurus I and DELVE 1 with simulations of the accreted satellite population of the Large Magellanic Cloud (LMC) and find that neither is likely to be associated with the LMC.
