EDGE: from quiescent to gas-rich to star-forming low-mass dwarf galaxies. Issue 2 (12th August 2020)

• Record Type: Journal Article
• Authors: Rey, Martin P; Pontzen, Andrew; Agertz, Oscar; Orkney, Matthew D A; Read, Justin I; Rosdahl, Joakim
• Is Part Of: Monthly notices of the Royal Astronomical Society. Volume 497:Issue 2(2020)
• Page Start: 1508
• Page End: 1520
• Publication Date: 2020-08-12
• Subjects: methods: numerical -- galaxies: dwarf -- galaxies: evolution -- galaxies: formation -- galaxies: haloes -- dark matter; Astronomy -- Periodicals; Periodicals; 520.5
• DOI: 10.1093/mnras/staa1640
• Languages: English
• ISSNs: 0035-8711

Abstract

ABSTRACT: We study how star formation is regulated in low-mass field dwarf galaxies ($10^5 \le M_{\star } \le 10^6 \, \mbox{M}_\mathrm{\odot }$ ), using cosmological high-resolution ($3 \, \mathrm{pc}$ ) hydrodynamical simulations. Cosmic reionization quenches star formation in all our simulated dwarfs, but three galaxies with final dynamical masses of $3 \times 10^{9} \, \mbox{M}_\mathrm{\odot }$ are subsequently able to replenish their interstellar medium by slowly accreting gas. Two of these galaxies reignite and sustain star formation until the present day at an average rate of $10^{-5} \, \mbox{M}_\mathrm{\odot } \, \text{yr}^{-1}$, highly reminiscent of observed low-mass star-forming dwarf irregulars such as Leo T. The resumption of star formation is delayed by several billion years due to residual feedback from stellar winds and Type Ia supernovae; even at z = 0, the third galaxy remains in a temporary equilibrium with a large gas content but without any ongoing star formation. Using the 'genetic modification' approach, we create an alternative mass growth history for this gas-rich quiescent dwarf and show how a small $(0.2\, \mathrm{dex})$ increase in dynamical mass can overcome residual stellar feedback, reigniting star formation. The interaction between feedback and mass build-up produces a diversity in the stellar ages and gas content of low-mass dwarfs, which will be probed by combining next-generation H i and imaging surveys.