Dwarf galaxy mass estimators versus cosmological simulations

Alejandro González-Samaniego, James S. Bullock, Michael Boylan-Kolchin, Alex Fitts, Oliver D. Elbert, Philip F. Hopkins, Dušan Kereš, Claude Andre Faucher-Giguère

Research output: Contribution to journalArticlepeer-review

21 Scopus citations


We use a suite of high-resolution cosmological dwarf galaxy simulations to test the accuracy of commonly used mass estimators from Walker et al. (2009) and Wolf et al. (2010), both of which depend on the observed line-of-sight velocity dispersion and the 2D half-light radius of the galaxy, Re. The simulations are part of the Feedback in Realistic Environments (FIRE) project and include 12 systems with stellar masses spanning 105-107 M that have structural and kinematic properties similar to those of observed dispersion-supported dwarfs. Both estimators are found to be quite accurate: MWolf/Mtrue = 0.98-0.12+0.19 and MWalker/Mtrue = 1.07-0.15+0.21, with errors reflecting the 68 per cent range over all simulations. The excellent performance of these estimators is remarkable given that they each assume spherical symmetry, a supposition that is broken in our simulated galaxies. Though our dwarfs have negligible rotation support, their 3D stellar distributions are flattened, with short-to-long axis ratios c/a ≃ 0.4-0.7. The median accuracy of the estimators shows no trend with asphericity. Our simulated galaxies have sphericalized stellar profiles in 3D that follow a nearly universal form, one that transitions from a core at small radius to a steep fall-off∝r-4.2 at large r; they are well fit by Sérsic profiles in projection. We find that the most important empirical quantity affecting mass estimator accuracy is Re. Determining Re by an analytic fit to the surface density profile produces a better estimated mass than if the half-light radius is determined via direct summation.

Original languageEnglish (US)
Pages (from-to)4786-4796
Number of pages11
JournalMonthly Notices of the Royal Astronomical Society
Issue number4
StatePublished - 2017


  • Dark matter
  • Galaxies: dwarf
  • Galaxies: fundamental parameters
  • Galaxies: kinematics and dynamics

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science


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