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The In Situ Origins of Dwarf Stellar Outskirts in FIRE-2

Kado-Fong, Erin and Sanderson, Robyn E. and Greene, Jenny E. and Cunningham, Emily C. and Wheeler, Coral and Chan, T. K. and El-Badry, Kareem and Hopkins, Philip F. and Wetzel, Andrew and Boylan-Kolchin, Michael and Faucher-Giguère, Claude-André and Huang, Song and Quataert, Eliot and Starkenburg, Tjitske (2022) 'The In Situ Origins of Dwarf Stellar Outskirts in FIRE-2.', The Astrophysical Journal, 931 (2). p. 152.


Extended, old, and round stellar halos appear to be ubiquitous around high-mass dwarf galaxies (108.5 < M⋆/M⊙ < 109.6) in the observed universe. However, it is unlikely that these dwarfs have undergone a sufficient number of minor mergers to form stellar halos that are composed of predominantly accreted stars. Here, we demonstrate that FIRE-2 (Feedback in Realistic Environments) cosmological zoom-in simulations are capable of producing dwarf galaxies with realistic structures, including both a thick disk and round stellar halo. Crucially, these stellar halos are formed in situ, largely via the outward migration of disk stars. However, there also exists a large population of “nondisky” dwarfs in FIRE-2 that lack a well-defined disk/halo and do not resemble the observed dwarf population. These nondisky dwarfs tend to be either more gas-poor or to have burstier recent star formation histories than the disky dwarfs, suggesting that star formation feedback may be preventing disk formation. Both classes of dwarfs underscore the power of a galaxy’s intrinsic shape—which is a direct quantification of the distribution of the galaxy’s stellar content—to interrogate the feedback implementation in simulated galaxies.

Item Type:Article
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Publisher statement:Original content from this work may be used under the terms of the Creative Commons Attribution 4.0 licence. Any further distribution of this work must maintain attribution to the author(s) and the title of the work, journal citation and DOI.
Date accepted:02 May 2022
Date deposited:14 July 2022
Date of first online publication:06 June 2022
Date first made open access:14 July 2022

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