Origin of stellar prolate rotation in a cosmologically simulated faint dwarf galaxy

Abstract

Stellar prolate rotation in dwarf galaxies is rather uncommon, with only two known galaxies in the Local Group showing such feature (Phoenix and And II). Cosmological simulations show that in massive early-type galaxies prolate rotation likely arises from major mergers. However, the origin of such kinematics in the dwarf galaxies regime has only been explored using idealized simulations. Here we made use of hydrodynamical cosmological simulations of dwarfs galaxies with stellar mass between $3\times 10^5$ and $5\times 10^8$ M${}_{\odot }$ to explore the formation of prolate rotators. Out of $27$ dwarfs, only one system showed clear rotation around the major axis, whose culprit is a major merger at $z=1.64$, which caused the transition from an oblate to a prolate configuration. Interestingly, this galaxy displays a steep metallicity gradient, reminiscent of the one measured in Phoenix and And II: this is the outcome of the merger event that dynamically heats old, metal-poor stars, and of the centrally concentrated residual star formation. Major mergers in dwarf galaxies offer a viable explanation for the formation of such peculiar systems, characterized by steep metallicity gradients and prolate rotation.

5 pages, 3 figures

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Cited by in corpus (6)

• The stellar metallicity gradients of Local Group dwarf galaxies
• A new class of dark matter-free dwarf galaxies? I. Clues from FCC 224, NGC 1052-DF2 and NGC 1052-DF4
• Metallicity profiles of Ultra Diffuse Galaxies in NIHAO simulations
• Kinematics and metallicity of the dwarf spheroidal galaxy Andromeda XVIII
• Reorientation Rates of Structural and Kinematic Axes in Simulated Massive Galaxies and the Origins of Prolate Rotation
• CROCODILE-DWARF: Assembly and Kinematics of Field Dwarf Galaxies with GADGET4-OSAKA