Skip to main content

Research Repository

Advanced Search

Unraveling the Complexity of Dwarf Galaxy Dynamics: A Study of Binary Orbital Motions

Wang, Wenting; Zhu, Ling; Jing, Yipeng; Grand, Robert J. J.; Li, Zhaozhou; Fu, Xiaoting; Li, Lu; Han, Jiaxin; Li, Ting S.; Feng, Fabo; Frenk, Carlos

Unraveling the Complexity of Dwarf Galaxy Dynamics: A Study of Binary Orbital Motions Thumbnail


Wenting Wang

Ling Zhu

Yipeng Jing

Robert J. J. Grand

Zhaozhou Li

Xiaoting Fu

Lu Li

Jiaxin Han

Ting S. Li

Fabo Feng


We investigate the impact of binary orbital motions on the dynamical modeling of dwarf galaxies with intrinsic line-of-sight velocity dispersions ( σvr ) of 1–9 km s−1. Using dwarf galaxies from the auriga level-2 and level-3 simulations, we apply the Jeans Anisotropic Multi-Gaussian Expansion modeling to tracer stars before and after including binaries to recover the dynamical masses. The recovered total masses within the half-mass radius of tracers, M(< r half), are always inflated due to binary motions, with greater inflations occurring for smaller σvr . However, many dwarf galaxies experience central density deflated due to binary motions, with little dependence on σvr . This is due to the negative radial gradients in the velocity dispersion profiles, with the fractional inflation in σvr due to binaries more significant in outskirts. An extreme binary fraction of 70% can lead to central density deflation of up to 10%–20% at 3 km s−1 < σvr < 8 km s−1, with M( < r half) inflated by 4% at 9 km s−1 and up to 15% at 3 km s−1. A lower binary fraction of 36% leads to similar deflations, with the inflations decreasing to approximately 10% at 3 km s−1 and becoming statistically insignificant. The choice of binary orbit distribution models does not result in significant differences, and observational errors tend to slightly weaken the deflations in the recovered central density. Two observations separated by 1 yr to exclude binaries lead to almost zero inflations/deflations for a binary fraction of 36% over 3 km s−1 < σvr<9 km s−1. For σvr∼1 km s−1 to 3 km s−1, a binary fraction of 70% (36%) still results in 60% (30%) to 10% (1%) of inflations in M( < r half), even with two-epoch observation.


Wang, W., Zhu, L., Jing, Y., Grand, R. J. J., Li, Z., Fu, X., …Frenk, C. (2023). Unraveling the Complexity of Dwarf Galaxy Dynamics: A Study of Binary Orbital Motions. Astrophysical Journal, 956(2), Article 91.

Journal Article Type Article
Acceptance Date Aug 21, 2023
Online Publication Date Oct 11, 2023
Publication Date Oct 1, 2023
Deposit Date Oct 17, 2023
Publicly Available Date Oct 17, 2023
Journal The Astrophysical Journal
Print ISSN 0004-637X
Publisher American Astronomical Society
Peer Reviewed Peer Reviewed
Volume 956
Issue 2
Article Number 91
Keywords Binary stars, Dark matter, Dwarf galaxies, Hydrodynamical simulations
Public URL


You might also like

Downloadable Citations