The spatial, kinematical, chemical and age properties of the intermediate Population Ⅱ (iPⅡ) are discussed in the context of constraining formation models. It is suggested that all the flattened populations named above are the same, or parts of the same, ubiquitous galactic component having broad kinematical and chemical distributions. The formation of the iPⅡ was likely independent from (although simultaneous with) that of the halo, along the lines of recent "dual halo models". However, it is still not clear whether the iPⅡ is a distinct population from, or an extension of, the thin disk, nor whether the iPⅡ formed in a dissipative collapse (distinct from the formation of the halo) or via the dynamical heating of an existing thin disk by the accretion of a galactic satellite into the disk.
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