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The Case for Strangulation in Low-Mass Hosts: DDO 113

We investigate the case for environmental quenching of the Fornax-mass satellite DDO 113, which lies only 9 kpc in projection from its host, the Large-Magellanic-Cloud-mass galaxy NGC 4214. DDO 113 was quenched about 1 Gyr ago and is virtually gas-free, while analogs in the field are predominantly star-forming and gas-rich. We use deep imaging obtained with the Large Binocular Telescope to show that DDO 113 exhibits no evidence of tidal disruption to a surface brightness of $μ_V\sim29$ mag $\text{arcsec}^{-2}$, based on both unresolved emission and resolved stars. Mass-analogs of DDO 113 in Illustris-1 with similar hosts, small projected separations, and no significant tidal stripping first fell into their host halo 2--6 Gyr ago, showing that tidal features (or lack thereof) can be used to constrain infall times in systems where there are few other constraints on the orbit of the satellite. With the infall time setting the clock for environmental quenching mechanisms, we investigate the plausibility of several such mechanisms. We find that strangulation, the cessation of cold gas inflows, is likely the dominant quenching mechanism for DDO 113, requiring a time-averaged mass-loading factor of $η=6-11$ for star-formation-driven outflows that is consistent with theoretical and observational constraints. Motivated by recent numerical work, we connect DDO 113's strangulation to the presence of a cool circumgalactic medium (CGM) around NGC 4214. This discovery shows that the CGM of low-mass galaxies can affect their satellites significantly and motivates further work on understanding the baryon cycle in low-mass galaxies.