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Probing dark matter with star clusters: a dark matter core in the ultra-faint dwarf Eridanus II

Research output: Contribution to journalArticle

  • Filippo Contenta
  • Eduardo Balbinot
  • James A. Petts
  • Justin I. Read
  • Mark Gieles
  • Michelle L. M. Collins
  • Jorge Peñarrubia
  • Maxime Delorme
  • Alessia Gualandris

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Original languageEnglish
JournalMonthly Notices of the Royal Astronomical Society
Publication statusPublished - 19 Feb 2018


We present a new technique to probe the central dark matter (DM) density profile of galaxies that harnesses both the survival and observed properties of star clusters. As a first application, we apply our method to the `ultra-faint' dwarf Eridanus II (Eri II) that has a lone star cluster ~45 pc from its centre. Using a grid of collisional $N$-body simulations, incorporating the effects of stellar evolution, external tides and dynamical friction, we show that a DM core for Eri II naturally reproduces the size, radial light profile and projected position of its star cluster. By contrast, a dense cusped galaxy requires the cluster to lie implausibly far from the centre of Eri II (>1 kpc), with a high inclination orbit that must be observed at a particular orbital phase. Our results imply that either a cold DM cusp was `heated up' at the centre of Eri II by bursty star formation, or we are seeing the first unambiguous evidence for physics beyond cold DM.

    Research areas

  • Astrophysics - Astrophysics of Galaxies

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