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          Institute: MPI für Astronomie     Collection: Publikationen_mpia     Display Documents

ID: 742474.0, MPI für Astronomie / Publikationen_mpia
The role of mergers and halo spin in shaping galaxy morphology
Authors:Rodriguez-Gomez, V.; Sales, L. V.; Genel, S.; Pillepich, A.; Zjupa, J.; Nelson, D.; Griffen, B.; Torrey, P.; Snyder, G. F.; Vogelsberger, M.; Springel, V.; Ma, C.-P.; Hernquist, L.
Date of Publication (YYYY-MM-DD):2017
Title of Journal:Monthly Notices of the Royal Astronomical Society
Start Page:3083
End Page:3098
Audience:Not Specified
Abstract / Description:Mergers and the spin of the dark matter halo are factors traditionally believed to determine the morphology of galaxies within a Λ cold dark matter (ΛCDM) cosmology. We study this hypothesis by considering approximately 18 000 central galaxies at z = 0 with stellar masses M* = 109-1012 M selected from the Illustris cosmological hydrodynamic simulation. The fraction of accreted stars - which measures the importance of massive, recent and dry mergers - increases steeply with galaxy stellar mass, from less than 5 per cent in dwarfs to 80 per cent in the most massive objects, and the impact of mergers on galaxy morphology increases accordingly. For galaxies with M* ≳ 1011 M, mergers have the expected effect: If gas-poor, they promote the formation of spheroidal galaxies, whereas gas-rich mergers favour the formation and survivability of massive discs. This trend, however, breaks at lower masses. For objects with M* ≲ 1011 M, mergers do not seem to play any significant role in determining the morphology, with accreted stellar fractions and mean merger gas fractions that are indistinguishable between spheroidal and disc-dominated galaxies. On the other hand, halo spin correlates with morphology primarily in the least massive objects in the sample (M* ≲ 1010 M), but only weakly for galaxies above that mass. Our results support a scenario where (1) mergers play a dominant role in shaping the morphology of massive galaxies, (2) halo spin is important for the morphology of dwarfs, and (3) the morphology of medium-sized galaxies - including the Milky Way - shows little dependence on galaxy assembly history or halo spin, at least when these two factors are considered individually.
Free Keywords:methods: numerical; galaxies: formation; galaxies: haloes; galaxies: interactions; galaxies: kinematics and dynamics; galaxies: structure
External Publication Status:published
Document Type:Article
Communicated by:N. N.
Affiliations:MPI für Astronomie
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