Characterizing the Infall Times and Quenching Timescales of Milky Way Satellites with $Gaia$ Proper Motions

Understand

Observations of low-mass satellite galaxies in the nearby Universe point towards a strong dichotomy in their star-forming properties relative to systems with similar mass in the field.

• Specifically, satellite galaxies are preferentially gas poor and no longer forming stars, while their field counterparts are largely gas rich and actively forming stars.
• Much of the recent work to understand this dichotomy has been statistical in nature, determining not just that environmental processes are most likely responsible for quenching these low-mass systems but also that they must operate very quickly after infall onto the host system, with quenching timescales $\lesssim 2~ {\rm Gyr}$ at ${M}_{\star} \lesssim 10^{8}~{\rm M}_{\odot}$.
• This work utilizes the newly-available $Gaia$ DR2 proper motion measurements along with the Phat ELVIS suite of high-resolution, cosmological, zoom-in simulations to study low-mass satellite quenching around the Milky Way on an object-by-object basis.