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EDGE: The Origin of Scatter in Ultra-faint Dwarf Stellar Masses and Surface Brightnesses

Rey, Martin P., Pontzen, Andrew, Agertz, Oscar, Orkney, Matthew, Read, Justin, Saintonge, Amélie and Pedersen, Christian (2019) EDGE: The Origin of Scatter in Ultra-faint Dwarf Stellar Masses and Surface Brightnesses Astrophysical Journal Letters, 886 (1).

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We demonstrate how the least luminous galaxies in the universe, ultra-faint dwarf galaxies, are sensitive to their dynamical mass at the time of cosmic reionization. We select a low-mass (~ ´ 1.5 10 M☉ 9 ) dark matter halo from a cosmological volume, and perform zoom hydrodynamical simulations with multiple alternative histories using “genetically modified” initial conditions. Earlier-forming ultra-faints have higher stellar mass today, due to a longer period of star formation before their quenching by reionization. Our histories all converge to the same final dynamical mass, demonstrating the existence of extended scatter (�1 dex) in stellar masses at fixed halo mass due to the diversity of possible histories. One of our variants builds less than 2% of its final dynamical mass before reionization, rapidly quenching in situ star formation. The bulk of its final stellar mass is later grown by dry mergers, depositing stars in the galaxy’s outskirts and hence expanding its effective radius. This mechanism constitutes a new formation scenario for highly diffuse (r1 2 ~ 820 pc, ~ - 32 mag arcsec 2 ), metal-poor ([Fe H 2.9 ] = - ), ultra-faint (V = -5.7) dwarf galaxies within the reach of next-generation low surface brightness surveys.

Item Type: Article
Divisions : Faculty of Engineering and Physical Sciences > Physics
Authors :
Rey, Martin P.
Pontzen, Andrew
Agertz, Oscar
Saintonge, Amélie
Pedersen, Christian
Date : 13 November 2019
DOI : 10.3847/2041-8213/ab53dd
Uncontrolled Keywords : Dwarf galaxies; Low surface brightness galaxies; Hydrodynamical simulations; Galaxy formation; Dark matter; Galaxy evolution; Astrophysics - Astrophysics of Galaxies; Astrophysics - Cosmology and Nongalactic Astrophysics
Depositing User : James Marshall
Date Deposited : 29 Jan 2020 11:11
Last Modified : 29 Jan 2020 11:11

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