The Magellanic Stream As A Laboratory For Gas Stripping And Dark Matter Halo Evolution In Dwarf Irregular Galaxies

The Magellanic Stream serves as one of the most important case studies for observing tidal stripping, ram pressure stripping, and the effects of dark matter halo evolution in dwarf irregular galaxies. Using an array of available tools, this paper attempts to resolve competing models of the Magellanic Stream's formation and address the structural implications of irregular dwarf galaxies and dark matter halos. The available evidence supports the hybrid model most clearly. Specifically, the clear inter-Cloud tidal stripping of the SMC by the LMC, gas ejection, and the ram pressure from the Milky Way's halo, which accelerates and shapes the ejected gas, explains the Stream's morphology and the Leading Arm formation, and the high velocity of the Clouds. This is consistent with SMC-like metallicities and the connection of the the bifurcated filaments to the Clouds. Contrary to the aforementioned models, pure ram pressure (Moore & Davis, 1994) and tidal models based on several close passages (Gardiner & Noguchi, 1996) fall short of describing several important aspects of the Stream and the Clouds of the Magellanic System. The interaction places numerous constraints on the evolution of dark matter halos in dwarf irregulars. Tidal stripping occurs in the outer halos of the Clouds, which truncates dark matter while the inner disk and stellar body remain intact. This is consistent with the disk kinematics of the LMC (Kallivayalil et al., 2013; Van Der Marel et al., 2002) and the structure of the SMC. Based on the Stream mass budget, the mass stripping efficiency suggests that the pre-infall SMC halo was more massive and extended than the current remnant and also agrees with the NFW prediction, which states that halos have cuspy and concentrated profiles that resist stripping in the inner regions, but are susceptible to stripping in the outer regions. Other effects on dwarf irregular galaxy evolution are that the inter-satellite preprocessing prior to the infall into the host-halo is relevant; that the density of the CGM is a factor in determining ram-pressure stripping at great distances from the center of the Galaxy; that gas is preferentially stripped over stars during early stripping, which enables the development of gas-poor but more morphologically regular descendants; and that the properties of the host halo have an effect on the gas-poor and morphologically regular descendants and the duration of the phenomena. Uncertainties continue to persist with regards to the complete mass of the Milky Way, the CGM density profile, Clouds pre-infall masses, the total ionized gas mass of the Stream, and the mass of the required numerical resolution required to model small-scale hydrodynamic instabilities. More extensive future developments of UV absorption studies with the next-generation UV satellites, deeper HI studies with the Square Kilometre Array, more accurate proper motion measurements with subsequent Gaia data releases, and high resolution cosmological simulations, among others, will aid in addressing these issues. The Magellanic System will be foundational in our attempts to understand the restructuring of baryonic and dark matter from dwarf irregular galaxies, as they traverse the circumgalactic environments of large hosts from the perspective of the active and massive hosts. The CGM Stripping is hierarchical and will also operate multiple mechanisms simultaneously. As an active participant, the CGM is not passive and these will be true for all group and cluster environments where dwarf galaxy transformation is known to take place.

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