A Preinfall Magellanic Analog–Corona and Stream Formation in the HESTIA Cosmological Simulations

Abstract We identify and investigate a preinfall analog of the Large and Small Magellanic Clouds (LMCs, SMCs) in the High-Resolution Environmental Simulations of the Immediate Area suite of constrained cosmological simulations. The system, dynamically isolated from the Local Group, evolves over ∼6 Gyr and forms a multiphase warm coronal halo and a neutral gas stream via repeated tidal interactions, ∼150 kpc in length. The LMC analog’s corona forms self-consistently through virial accretion and inhibits the survival of clumpy neutral structures beyond ∼600 Myr. The SMC analog remains bound through to z = 0, and the pair also exhibits bridge-like and leading-arm features. These results suggest that while most of the ionized stream is formed by the LMC coronal gas, the neutral gas stream, bridge, and leading arm components of the Magellanic System can arise from dwarf–dwarf interactions prior to infall, while the survival and ionization of these features likely require additional environmental processing. Furthermore, we identify a stellar component out of phase to the neutral component of the stream, implying that if the Magellanic stellar stream exists, it may not be spatially coexistent to the dominant H i stream. This system offers a valuable preinfall reference point for interpreting the Magellanic System and identifying analogs beyond the Local Group.