We study how star formation is regulated in low-mass field dwarf galaxies ( 10 ^ { 5 } \leq M _ { \star } \leq 10 ^ { 6 } \textup { M } _ { \mathrm { \sun } } ) , 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 } \textup { M } _ { \mathrm { \sun } } 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 } \textup { M } _ { \mathrm { \sun } } \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 H i and imaging surveys .