The dual role of outflows in quenching satellites of low-mass hosts: NGC 3109

Abstract

ABSTRACT While dwarf galaxies observed in the field are overwhelmingly star forming, dwarf galaxies in environments as dense or denser than the Milky Way are overwhelmingly quenched. In this paper, we explore quenching in the lower density environment of the Small-Magellanic-Cloud-mass galaxy NGC 3109 (M$_* \sim 10^8 \, \text{M}_\odot$), which hosts two known dwarf satellite galaxies (Antlia and Antlia B), both of which are ${\rm H}\, \rm{\small I}$ deficient compared to similar galaxies in the field and have recently stopped forming stars. Using a new semi-analytic model in concert with the measured star formation histories and gas masses of the two dwarf satellite galaxies, we show that they could not have been quenched solely by direct ram pressure stripping of their interstellar media, as is common in denser environments. Instead, we find that separation of the satellites from pristine gas inflows, coupled with stellar-feedback-driven outflows from the satellites (jointly referred to as the starvation quenching model), can quench the satellites on time-scales consistent with their likely infall times into NGC 3109’s halo. It is currently believed that starvation is caused by ‘weak’ ram pressure that prevents low-density, weakly bound gas from being accreted on to the dwarf satellite, but cannot directly remove the denser interstellar medium. This suggests that star-formation-driven outflows serve two purposes in quenching satellites in low-mass environments: outflows from the host form a low-density circumgalactic medium that cannot directly strip the interstellar media from its satellites, but is sufficient to remove loosely bound gaseous outflows from the dwarf satellites driven by their own star formation.