The role of mergers and halo spin in shaping galaxy morphology
Name
1609.09498.pdf
Description
Accepted version
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1.65 MB
Format
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Checksum (MD5)
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Author(s)
Rodriguez-Gomez, Vicente
Sales, Laura V
Genel, Shy
Pillepich, Annalisa
Zjupa, Jolanta
Nelson, Dylan
Griffen, Brendan
Torrey, Paul
Snyder, Gregory F
Vogelsberger, Mark
Date Issued
2017
Journal
Monthly Notices of the Royal Astronomical Society
Publisher
Oxford University Press (OUP)
Citation
Rodriguez-Gomez, Vicente, et al. "The Role of Mergers and Halo Spin in Shaping Galaxy Morphology." Monthly Notices of the Royal Astronomical Society 467 3 (2017): 3083-98.
Version
Author's final manuscript
Abstract
© 2017 The Authors Published by Oxford University Press on behalf of the Royal Astronomical Society 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.
MIT Department
Massachusetts Institute of Technology. Department of Physics
MIT Kavli Institute for Astrophysics and Space Research
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DOI of Published Version
https://doi.org/10.1093/MNRAS/STX305
