Volume 611, March 2018
|Number of page(s)||5|
|Section||Letters to the Editor|
|Published online||16 March 2018|
Letter to the Editor
Stellar metallicity variations across spiral arms in disk galaxies with multiple populations
GEPI, Observatoire de Paris, PSL Université, CNRS,
5 Place Jules Janssen,
2 Observatoire de Paris, LERMA, CNRS, PSL Univ., UPMC, Sorbonne Univ., 75014 Paris, France
3 Collège de France, 11 Place Marcelin Berthelot, 75005 Paris, France
Accepted: 24 January 2018
This Letter studies the formation of azimuthal metallicity variations in the disks of spiral galaxies in the absence of initial radial metallicity gradients. Using high-resolution N-body simulations, we model composite stellar discs, made of kinematically cold and hot stellar populations, and study their response to spiral arm perturbations. We find that, as expected, disk populations with different kinematics respond differently to a spiral perturbation, with the tendency for dynamically cooler populations to show a larger fractional contribution to spiral arms than dynamically hotter populations. By assuming a relation between kinematics and metallicity, namely the hotter the population, the more metal-poor it is, this differential response to the spiral arm perturbations naturally leads to azimuthal variations in the mean metallicity of stars in the simulated disk. Thus, azimuthal variations in the mean metallicity of stars across a spiral galaxy are not necessarily a consequence of the reshaping, by radial migration, of an initial radial metallicity gradient. They indeed arise naturally also in stellar disks which have initially only a negative vertical metallicity gradient.
Key words: galaxies: evolution / galaxies: kinematics and dynamics / galaxies: structure
© ESO 2018
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