The no-spin zone: rotation versus dispersion support in observed and simulated dwarf galaxies

• DOI: 10.1093/mnras/stw2583
• Publication Date: 2016-10-09T00:29:46Z
• Authors: Coral Wheeler; Andrew B. Pace; James S. Bullock; Michael Boylan-Ko...; Jose Oñorbe; Oliver D. Elbert; Alex Fitts; Philip F. Hopkins; Dušan Kereš
• Keywords: Velocity dispersion; Sigma; Dwarf spheroidal galaxy

We perform a systematic Bayesian analysis of rotation versus dispersion support (vrot/σ) in 40 dwarf galaxies throughout the local volume (LV) over stellar mass range |$10^{3.5} \rm \, M_{{\odot }}< M_{\rm \star }< 10^{8} }}$|⁠. find that stars ∼80 per cent LV studied – both satellites and isolated systems are dispersion-supported. In particular, we show 6/10 dwarfs our sample have vrot/σ ≲ 1.0, while all 2.0. These results challenge traditional view gas-rich irregulars (dIrrs) distributed cold, rotationally supported discs, gas-poor spheroidals (dSphs) kinematically distinct having dispersion-supported stars. see no clear trend between distance to closest L⋆ galaxy, nor M⋆ within range. apply same four fire hydrodynamic zoom-in simulations (⁠|$10^9 {vir}}< 10^{10} }}$|⁠) simulated dIrr ellipticities ratios consistent with observed population dIrrs dSphs without need subject these any external perturbations or tidal forces. posit most form as puffy, dispersion-dominated systems, rather than angular-momentum-supported discs. If this is case, then transforming into dSph may require little more removing its gas.