Journal
ASTROPHYSICAL JOURNAL LETTERS
Volume 824, Issue 1, Pages -Publisher
IOP PUBLISHING LTD
DOI: 10.3847/2041-8205/824/1/L14
Keywords
galaxies: dwarf; galaxies: individual (Eridanus II); galaxies: photometry; galaxies: stellar content
Categories
Funding
- NSF [AST-1412504, AST-1311326, AST-1151462]
- Smithsonian Astro-physical Observatory
- Direct For Mathematical & Physical Scien
- Division Of Astronomical Sciences [1151462] Funding Source: National Science Foundation
- Division Of Astronomical Sciences
- Direct For Mathematical & Physical Scien [1821987, 1412504] Funding Source: National Science Foundation
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We present deep imaging of the most distant dwarf discovered by the Dark Energy Survey, Eridanus II (Eri II). Our Magellan/ Megacam stellar photometry reaches similar to 3 mag deeper than previous work and allows us to confirm the presence of a stellar cluster whose position is consistent with Eri II's center. This makes Eri II, at M-V = -7.1, the least luminous galaxy known to host a (possibly central) cluster. The cluster is partially resolved, and at MV = -3.5 it accounts for similar to 4% of Eri II's luminosity. We derive updated structural parameters for Eri II, which has a half-light radius of similar to 280 pc and is elongated (epsilon similar to 0.48) at a measured distance of D similar to 370 kpc. The color-magnitude diagram displays a blue, extended horizontal branch, as well as a less populated red horizontal branch. A central concentration of stars brighter than the old main-sequence turnoff hints at a possible intermediate-age (similar to 3 Gyr) population; alternatively, these sources could be blue straggler stars. A deep Green Bank Telescope observation of Eri II reveals no associated atomic gas.
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