Kinematics of the Tucana Dwarf Galaxy: an unusually dense dwarf in the Local Group. Issue 2 (20th February 2019)

• Record Type: Journal Article
• Authors: Gregory, Alexandra L; Collins, Michelle L M; Read, Justin I; Irwin, Michael J; Ibata, Rodrigo A; Martin, Nicolas F; McConnachie, Alan W; Weisz, Daniel R
• Is Part Of: Monthly notices of the Royal Astronomical Society. Volume 485:Issue 2(2019)
• Page Start: 2010
• Page End: 2025
• Publication Date: 2019-02-20
• Subjects: galaxies: dwarf -- galaxies: evolution -- galaxies: haloes -- galaxies: kinematics and dynamics -- Local Group; Astronomy -- Periodicals; Periodicals; 520.5
• DOI: 10.1093/mnras/stz518
• Languages: English
• ISSNs: 0035-8711

Abstract

Abstract: We present new FLAMES+GIRAFFE spectroscopy of 36 member stars in the isolated Local Group dwarf spheroidal galaxy Tucana. We measure a systemic velocity for the system of$v_{\mathrm{Tuc}} = 216.7_{-2.8}^{+2.9}$ km s −1, and a velocity dispersion of$\sigma _{\mathrm{v, Tuc}} = 14.4_{-2.3}^{+2.8}$ km s −1 . We also detect a rotation gradient of$\frac{{\rm d}v_{r}}{{\rm d}\chi } = 7.6^{+4.2}_{-4.3}$ km s −1 kpc −1, which reduces the systemic velocity to$v_{\mathrm{Tuc}} = 215.2_{-2.7}^{+2.8}$ km s −1 and the velocity dispersion to$\sigma _{v, \mathrm{Tuc}} = 13.3_{-2.3}^{+2.7}$ km s −1 . We perform Jeans modelling of the density profile of Tucana, using the line-of-sight velocities of the member stars. We find that it favours a high central density consistent with 'pristine' subhaloes in Λ cold dark matter, and a massive dark matter halo (∼10 10 M⊙ ) consistent with expectations from abundance matching. Tucana appears to be significantly more centrally dense than other isolated Local Group dwarfs, making it an ideal laboratory for testing dark matter models.