The standard cosmological model, known as Lambda Cold Dark Matter (ΛCDM), predicts that structures such as galaxies form hierarchically. In this framework, larger galaxies grow by accreting smaller ones, which are the first systems to form and act as the building blocks of the Universe.
However, the accretion of dwarf galaxies by larger systems like our Milky Way (MW) is not instantaneous. Dwarf galaxies can orbit their massive hosts as satellites for billions of years before fully merging with them. During this period, satellite galaxies are subjected to several physical processes that gradually quench their star formation by removing their reservoirs of cold gas and preventing the supply of new gas from their surroundings. These quenching mechanisms are known to be highly effective in the Local Group (LG), where almost all satellites of MW and M31 are quenched except for the most massive ones. Nevertheless, their effectiveness in MW-analogs beyond the LG, such as those observed in the SAGA and ELVES surveys, remains under debate.
To study the physics that drives satellite quenching, we rely on cosmological hydrodynamic simulations. In this work, we use the AGORA CosmoRun suite of cosmological zoom-in simulations of MW–mass halos. This suite resimulates the same MW-mass halo from the early Universe to the present day using different numerical codes, each employing distinct methods to solve the hydrodynamic equations and its own prescription for supernova (SN) feedback. By comparing the results from these simulations, we can assess how sensitive satellite quenching is to the chosen hydrodynamic method and feedback model, and evaluate how well our simulations reproduce observed properties.
To better understand the physical mechanisms involved in quenching, we examine the relative importance of several quenching mechanisms, such as ram-pressure stripping and tidal stripping, among others. Ram-pressure stripping occurs when the gas in a satellite galaxy is removed by the drag force exerted as it moves through the hot gas of the host halo. Tidal stripping, on the other hand, results from gravitational tidal forces that remove dark matter, stars, and gas from the satellite, often leading to the formation of extended stellar streams.
Our results show that the fraction of quenched satellites and quenching timescales in the simulations agrees well with observations, within the host-to-host scatter. We find that ram-pressure stripping and the cutoff of cold gas inflows are the dominant quenching mechanisms in satellites of MW-mass halos. However, the efficiency of these processes is strongly dependent on the specific implementation of SN feedback. These differences in efficiency may lead to variations in the colors of satellite galaxies and, potentially, of tidally stripped stellar streams.
The ARRAKIHS mission will observe the formation of stellar streams and, using the information obtained from the four different filters, will give us information on their colors. From this color data, it will be possible to determine the fraction of quenched satellite galaxies as well as the physical properties of the stellar streams themselves. Comparing these ARRAKIHS observations with simulations that use different dark matter and baryonic physics models will be extremely valuable for constraining our theoretical models and disentangling the physical processes that regulate satellite quenching and disruption in the Universe.
Read the complete paper by Rodríguez-Cardoso, R., et al. here.
