A New Low-Luminosity Cluster in the Outskirts of the Milky Way

GMOS image of Kim 2, in g band. The image is 4 arcminutes across.

New discoveries, and detailed measurement, of the stellar populations in the outer reaches of the Milky Way reveal the history of our Galaxy. Dongwon Kim (Australian National University) and collaborators contribute to our understanding by reporting on the discovery of a faint, low-density stellar cluster, called Kim 2, in the outer Milky Way halo. The cluster is ten-times more distant than typical globular clusters and shows signs of having lost significant mass. Measurements of metallicity suggest that Kim 2 was previously located in a dwarf Milky Way satellite galaxy and only recently accreted into the halo of our Galaxy. The cluster was discovered using the Dark Energy Camera (DECam) at CTIO, with confirmation and follow-up observations (see figure) using GMOS on Gemini South. Full results are posted in a preprint and will be published in the Astrophysical Journal. Look for a Gemini press release later this week.