EDGE: From quiescent to gas-rich to star-forming low-mass dwarf galaxies
  We study how star formation is regulated in low-mass field dwarf galaxies
($10^5 \leq M_{\star} \leq 10^6 \, \text{M}_{\odot}$), using cosmological
high-resolution ($3 \, \text{pc}$) hydrodynamical simulations. Cosmic
reionization quenches star formation in all our simulated dwarfs, but three
galaxies with final dynamical masses of $3 \times 10^{9} \,\text{M}_{\odot}$
are subsequently able to replenish their interstellar medium by slowly
accreting gas. Two of these galaxies re-ignite and sustain star formation until
the present day at an average rate of $10^{-5} \, \text{M}_{\odot} \,
\text{yr}^{-1}$, 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, re-igniting
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 HI and imaging surveys.
