Vertical disc heating in Milky Way-sized galaxies in a cosmological context

Vertically extended, high velocity dispersion stellar distributions appear to be a ubiquitous feature of disc galaxies, and both internal and external mechanisms have been proposed to be the major driver of their formation. However, it is unclear to what extent each mechanism can generate such a dis...

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Published inMonthly notices of the Royal Astronomical Society Vol. 459; no. 1; pp. 199 - 219
Main Authors Grand, Robert J. J., Springel, Volker, Gómez, Facundo A., Marinacci, Federico, Pakmor, Rüdiger, Campbell, David J. R., Jenkins, Adrian
Format Journal Article
LanguageEnglish
Published London Oxford University Press 11.06.2016
Subjects
Accretion disks
Adiabatic flow
Coolers
Cosmology
Disks
Fluid mechanics
Galaxies
Heating
Kinematics
Milky Way
Orbits
Perturbation methods
Simulation
Star & galaxy formation
Symbols
galaxies: formation
galaxies: structure
galaxies: kinematics and dynamics
methods: numerical
galaxies: evolution
galaxies: spiral
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Summary:Vertically extended, high velocity dispersion stellar distributions appear to be a ubiquitous feature of disc galaxies, and both internal and external mechanisms have been proposed to be the major driver of their formation. However, it is unclear to what extent each mechanism can generate such a distribution, which is likely to depend on the assembly history of the galaxy. To this end, we perform 16 high-resolution cosmological-zoom simulations of Milky Way-sized galaxies using the state-of-the-art cosmological magnetohydrodynamical code arepo, and analyse the evolution of the vertical kinematics of the stellar disc in connection with various heating mechanisms. We find that the bar is the dominant heating mechanism in most cases, whereas spiral arms, radial migration and adiabatic heating from mid-plane density growth are all subdominant. The strongest source, though less prevalent than bars, originates from external perturbations from satellites/subhaloes of masses log10(M/M⊙) ≳ 10. However, in many simulations the orbits of newborn star particles become cooler with time, such that they dominate the shape of the age–velocity dispersion relation and overall vertical disc structure unless a strong external perturbation takes place.
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ISSN:0035-8711
1365-2966
DOI:10.1093/mnras/stw601