DEEP IMAGING of ERIDANUS II and ITS LONE STAR CLUSTER

D. Crnojević, D. J. Sand, D. Zaritsky, K. Spekkens, B. Willman, J. R. Hargis

Research output: Contribution to journalArticle

31 Scopus citations

Abstract

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 ∼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 Mv = -7.1, the least luminous galaxy known to host a (possibly central) cluster. The cluster is partially resolved, and at it accounts for ∼4% of Eri II's luminosity. We derive updated structural parameters for Eri II, which has a half-light radius of ∼280 pc and is elongated ( ∼ 0.48) at a measured distance of D ∼ 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 (∼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.

Original languageEnglish (US)
Article numberL14
JournalAstrophysical Journal Letters
Volume824
Issue number1
DOIs
StatePublished - Jun 10 2016

Keywords

  • galaxies: dwarf
  • galaxies: individual (Eridanus II)
  • galaxies: photometry
  • galaxies: stellar content

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science

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    Crnojević, D., Sand, D. J., Zaritsky, D., Spekkens, K., Willman, B., & Hargis, J. R. (2016). DEEP IMAGING of ERIDANUS II and ITS LONE STAR CLUSTER. Astrophysical Journal Letters, 824(1), [L14]. https://doi.org/10.3847/2041-8205/824/1/L14