Quenching Timescales of Dwarf Satellites around Milky Way–mass Hosts

Abstract

Observations of the low-mass satellites in the Local Group have shown high fractions of gas-poor, quiescent galaxies relative to isolated dwarfs, implying that the host halo environment plays an important role in the quenching of dwarf galaxies. In this work, we present measurements of the quenched fractions and quenching timescales of dwarf satellite galaxies in the DC Justice League suite of four high-resolution cosmological zoom-in simulations of Milky Way–mass halos. We show that these simulations accurately reproduce the satellite luminosity functions of observed nearby galaxies, as well as the variation in satellite quenched fractions from M * ∼ 10 5 M ⊙ to 10 10 M ⊙ . We then trace the histories of satellite galaxies back to z ∼ 15 and find that many satellites with M * ∼ 10 6 −10 8 M ⊙ quench within ∼2 Gyr of infall into the host halo, while others in the same mass range remain star-forming for as long as 5 Gyr. We show that this scatter can be explained by the satellite’s gas mass and the ram pressure it feels at infall. Finally, we identify a characteristic stellar mass scale of 10 8 M ⊙ above which infalling satellites are largely resistant to rapid environmental quenching.