Probing dark matter with star clusters: a dark matter core in the ultra-faint dwarf Eridanus II. Issue 3 (19th February 2018)

• Record Type: Journal Article
• Authors: Contenta, Filippo; Balbinot, Eduardo; Petts, James A; Read, Justin I; Gieles, Mark; Collins, Michelle L M; Peñarrubia, Jorge; Delorme, Maxime; Gualandris, Alessia
• Is Part Of: Monthly notices of the Royal Astronomical Society. Volume 476:Issue 3(2018)
• Page Start: 3124
• Page End: 3136
• Publication Date: 2018-02-19
• Subjects: stars: kinematics and dynamics -- galaxies: dwarf -- galaxies: haloes -- galaxies: individual: Eridanus II -- galaxies: star clusters: general -- galaxies: structure; Astronomy -- Periodicals; Periodicals; 520.5
• DOI: 10.1093/mnras/sty424
• Languages: English
• ISSNs: 0035-8711

Abstract

Abstract: 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 and the 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, therefore, favour a DM core. This implies that either a cold DM cusp was 'heated up' at the centre of Eri II by bursty star formation or we are seeing an evidence for physics beyond cold DM.