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Paper: Understanding the Formation and Evolution of Disk Outskirts: Results from Simulations
Volume: 396, Formation and Evolution of Galaxy Disks
Page: 201
Authors: Debattista, V.P.; Roskar, R.; Stinson, G.; Quinn, T.R.; Kaufmann, T.; Wadsley, J.
Abstract: In the standard scenario, disk galaxies form from the inside out; disk outskirts therefore are expected to present the most direct view of disk assembly. Here I explore the formation and evolution of disk outskirts, focusing especially on the surface density breaks commonly found there. I first show that the substantial angular momentum redistribution induced by bars via coupled spirals gives rise to profiles with breaks at large radii. The break in NGC 7079 is possibly of this type. However bars cannot account for breaks in unbarred galaxies, so other mechanisms must be acting. Recent high resolution galaxy formation simulations produce breaks via drops in star formation (SF). The outer disk in these simulations form self-consistently from stars scattered on nearly circular orbits from the inner disk by spirals. The resulting profile is therefore a consequence of the interplay between a SF drop and redistribution by secular processes. An important success of this model is that the resulting break radius is identical for all stars regardless of age or location relative to the mid-plane, as HST found in NGC 4244.
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