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Article Dans Une Revue Monthly Notices of the Royal Astronomical Society Année : 2023

Andromeda XXV -- a dwarf galaxy with a low central dark matter density

Emily J.E. Charles
  • Fonction : Auteur
Michelle L.M. Collins
  • Fonction : Auteur
R. Michael Rich
  • Fonction : Auteur
Justin I. Read
  • Fonction : Auteur
Stacy Y. Kim
  • Fonction : Auteur
Scott C. Chapman
  • Fonction : Auteur
Eduardo Balbinot
  • Fonction : Auteur
Daniel R. Weisz
  • Fonction : Auteur

Résumé

Andromeda (And) XXV has previously been reported as a dwarf spheroidal galaxy (dSph) with little-to-no dark matter. However, the uncertainties on this result were significant. In this study, we double the number of member stars and re-derive the kinematics and mass of And XXV. We find that And XXV has a systemic velocity of $\nu_\mathrm{r}=-107.7\pm1.0 \mathrm{~km s}^{-1}$ and a velocity dispersion of $\sigma_\nu=4.5\pm1.0\mathrm{~km s}^{-1}$. With this better constrained velocity dispersion, we derive a mass contained within the half-light radius of $M(r< r_\mathrm{h})=6.9^{+3.2}_{-2.8}\times10^6\mathrm{~M}_\odot$. This mass corresponds to a mass-to-light ratio of $\mathrm{[M/L]}_\mathrm{r_\mathrm{h}}=37^{+17}_{-15}\mathrm{~M}_\odot/\mathrm{L}_\odot$, demonstrating, for the first time, that And XXV has an unambiguous dark matter component. We also measure the metallicity of And XXV to be $\mathrm{[Fe/H]}=-1.9\pm0.1$$\mathrm{~}$dex, which is in agreement with previous results. Finally, we extend the analysis of And XXV to include mass modelling using GravSphere. We find that And XXV has a low central dark matter density, $\rho_\mathrm{DM}(150\mathrm{pc})= 2.7^{+1.8}_{-1.6}\times10^7\mathrm{~M}_\odot\mathrm{kpc}^{-3}$, making And XXV a clear outlier when compared to other Local Group (LG) dSphs of the similar stellar mass. In a companion paper, we will explore whether some combination of dark matter cusp-core transformations and/or tides can explain And XXV's low density.
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Dates et versions

hal-03815558 , version 1 (16-02-2024)

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Emily J.E. Charles, Michelle L.M. Collins, R. Michael Rich, Justin I. Read, Stacy Y. Kim, et al.. Andromeda XXV -- a dwarf galaxy with a low central dark matter density. Monthly Notices of the Royal Astronomical Society, 2023, 521 (3), pp.3527-3539. ⟨10.1093/mnras/stad752⟩. ⟨hal-03815558⟩
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