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Paper: The Upside Down Construction of a Simulated Disk Galaxy
Volume: 480, Structure and Dynamics of Disk Galaxies
Page: 105
Authors: Bird, J. C.; Kazantzidis, S.; Weinberg, D. H.; Guedes, J.; Callegari, S.; Mayer, L.; Madau, P.
Abstract: We analyze the dynamical evolution of stellar age cohorts, groups of stars with similar formation times, to determine the detailed structure formation history of the cosmological simulation of the formation of a disk galaxy similar to the Milky Way (the “Eris” simulation). There is a remarkably smooth correlation between structure and stellar age at z = 0, going from spheroidal distributions for the oldest stars to long, thin disks for the youngest populations. We find the velocity dispersion of a cohort increases monotonically with age. The smooth relationships between stellar age, structure, and dynamics seen at z = 0, which agree nicely with the observed properties of mono-abundance populations in the Milky Way, are largely established by the disk formation process. Stars continuously form as the initially spheroidal gas reservoir cools and contracts, increasing its rotational support and becomingly progressively longer and vertically thinner. Thus, the stellar disk forms “inside-out” radially and “upside-down” vertically.
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