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Paper: Origins of Disks in Simulations of Spiral Galaxies
Volume: 480, Structure and Dynamics of Disk Galaxies
Page: 97
Authors: Sales, L. V.
Abstract: We explore the factors that determine the morphology of galaxies within the ΛCDM scenario using the cosmological hydrodynamical simulations GIMIC to study the assembly and evolution of about 100 objects with masses comparable to the Milky Way. At z = 0, galaxies show a wide variety of morphologies, from dispersion-dominated systems to archetypical disk galaxies. Contrary to common belief, the present-day morphologies are only poorly correlated with the properties of the dark matter halos (such as merger history, assembly, and overall spin). Instead, we identify two important factors that determine the present-day morphologies: i) the alignment of the angular momentum of the baryons that accrete over time to form the galaxy, and ii) the fraction of baryons accreted via the hot corona. Disks tend to form when the spin of newly-accreted gas is well aligned with that of the galaxy already in place, whereas misalignments drive the growth of spheroids. The mode of gas accretion is also important. Disks form in halos where the contribution of hot accretion is maximized. This follows as cooling of gas from the hot-phase provides a slower channel of gas supply that guarantees its availability at later times to build up the young star-forming disks that we observe today.
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