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Dwarf galaxy mass estimators versus cosmological simulations

González-Samaniego, Alejandro and Bullock, James S. and Boylan-Kolchin, Michael and Fitts, Alex and Elbert, Oliver D. and Hopkins, Philip F. and Kereš, Dušan and Faucher-Giguère, Claude-André (2017) Dwarf galaxy mass estimators versus cosmological simulations. Monthly Notices of the Royal Astronomical Society, 472 (4). pp. 4786-4796. ISSN 0035-8711. PMCID PMC6350817.

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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, R_e. The simulations are part of the Feedback in Realistic Environments (FIRE) project and include 12 systems with stellar masses spanning 10^5–10^7 M⊙ that have structural and kinematic properties similar to those of observed dispersion-supported dwarfs. Both estimators are found to be quite accurate: M_(Wolf)/M_(true) = 0.98^(+0.19)_(−0.12) and M_(Walker)/M_(true) = 1.07^(+0.21)_(−0.15), 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 R_e. Determining R_e 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.

Item Type:Article
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URLURL TypeDescription CentralArticle Paper
Bullock, James S.0000-0003-4298-5082
Boylan-Kolchin, Michael0000-0002-9604-343X
Fitts, Alex0000-0002-8928-6011
Hopkins, Philip F.0000-0003-3729-1684
Kereš, Dušan0000-0002-1666-7067
Faucher-Giguère, Claude-André0000-0002-4900-6628
Additional Information:© 2017 The Authors. Published by Oxford University Press on behalf of the Royal Astronomical Society. Accepted 2017 September 5. Received 2017 August 16; in original form 2017 June 15. Published: 07 September 2017. AG-S was supported by a UC-MEXUS Fellowship. JSB and OE were supported by NSF grant AST-1518291. JSB was also supported by HST theory programs AR-13921, AR-13888 and AR-14282.001 and program number HST-GO-13343. These HST programs were provided by NASA through a grant from the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Incorporated, under NASA contract NAS5-26555. MBK and AF acknowledge support from the National Science Foundation (grant AST-1517226). MBK was also partially supported by NASA through grant NNX17AG29G and HST theory grants (programs AR-12836, AR-13888, AR-13896 and AR-14282) awarded by the Space Telescope Science Institute (STScI), which is operated by the Association of Universities for Research in Astronomy (AURA), Inc., under NASA contract NAS5-26555. DK was supported by NSF grant AST-1412153 and the Cottrell Scholar Award from the Research Corporation for Science Advancement. CAFG was supported by NSF through grants AST-1412836 and AST-1517491, and by NASA through grant NNX15AB22G. This work used computational resources of the University of Texas at Austin and the Texas Advanced Computing Center (TACC;, the NASA Advanced Supercomputing (NAS) Division and the NASA Center for Climate Simulation (NCCS) through allocation SMD-16-7760, and the Extreme Science and Engineering Discovery Environment (XSEDE, via allocation TG-AST140080), which is supported by National Science Foundation grant number OCI-1053575. This research made use of astropy (Astropy Collaboration et al. 2013).
Group:TAPIR, Astronomy Department
Funding AgencyGrant Number
NASA Hubble FellowshipAR-13921
NASA Hubble FellowshipAR-13888
NASA Hubble FellowshipAR-14282.001
NASA Hubble FellowshipHST-GO-13343
NASA Hubble FellowshipAR-12836
NASA Hubble FellowshipAR-13896
NASA Hubble FellowshipAR-14282
Research CorporationUNSPECIFIED
Subject Keywords:galaxies: dwarf – galaxies: fundamental parameters – galaxies: kinematics and dynamics – dark matter
Issue or Number:4
PubMed Central ID:PMC6350817
Record Number:CaltechAUTHORS:20171211-105754834
Persistent URL:
Official Citation:Alejandro González-Samaniego, James S. Bullock, Michael Boylan-Kolchin, Alex Fitts, Oliver D. Elbert, Philip F. Hopkins, Dušan Kereš, Claude-André Faucher-Giguère; Dwarf galaxy mass estimators versus cosmological simulations, Monthly Notices of the Royal Astronomical Society, Volume 472, Issue 4, 21 December 2017, Pages 4786–4796,
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:83798
Deposited By: Tony Diaz
Deposited On:12 Dec 2017 22:22
Last Modified:15 Nov 2019 04:07

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