Volume 572, December 2014
|Number of page(s)||19|
|Section||Galactic structure, stellar clusters and populations|
|Published online||03 December 2014|
Comparison between the SFH (as a function of cosmic time) of the simulation and the chemical evolution model. Different colors correspond to different disk radii, as indicated. Good overall agreement is found for most radii.
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In Fig. A.1 we compare the SFH (as a function of cosmic time) of the simulation with that used for the chemical evolution model. Different colors correspond to different disk radii, as indicated. Good overall agreement is found for most radii. Some discrepancy can be seen at 2 and 4 kpc approximately at t> 3 and t> 5 Gyr, respectively, where the simulation SFH is somewhat stronger. On the other hand, at early times the simulation SFH for r ≥ 4 kpc is lower than the chemical model SFH. This means that the disk inside-out growth in somewhat delayed in the
simulation. As discussed in Paper I, we have assumed that these differences between the simulation and chemical model are not crucial for the dynamics. However, we weight the stars in the simulation to satisfy the SFH in the chemical model, which is important for obtaining the correct mixture of populations corresponding to the chemistry.
Appendix B: Variations in chemo-kinematic properties with radius and distance from the disk midplane
Figures B.1 and B.2 present similar information to Figs. 5 and 8, but for two different distances from the disk midplane, as indicated. For each 2 kpc annulus a sample close to the plane (| z | < 0.5 kpc) and farther from the plane (0.5 < | z | < 3 kpc) is plotted. The dashed-pink lines in the first two columns show the mean. The decrease in age with Galactic radius can be seen in the densest contour levels (especially at 0.5 < | z | < 3 kpc), which do not extend to young ages for the inner radial bins. For the samples away from the plane shifts in the distributions are seen to lower birth-radii, lower metallicities and higher [Mg/Fe], as expected for older populations.
We note that the [Fe/H]-[Mg/Fe] plane does not show a discontinuity, as frequently seen in observations. We demonstrated in Paper I that a kinematically biased samples can give rise to this division between the thin and thick disks in the solar vicinity. However, as currently debated in the literature (Fuhrmann 2011; Anders et al. 2014; Bovy et al. 2012a), this gap may not be an artifact, but a real feature reflecting variations in the SFH of the MW disk. If this is confirmed in observations, it will serve as an additional constraint for our model, requiring the modification of its SFH and early chemistry. Except for the chemical discontinuity, no significant changes in the results presented in Paper I and the current work are expected.
Predictions for chemo-kinematic properties at different distances from the Galactic center (see also Fig. B.2). For each 2 kpc annulus a sample close to the plane (| z | < 0.5 kpc) and farther from the plane (0.5 < | z | < 3 kpc) is plotted. The dashed-pink lines in the first two columns show the mean.
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© ESO, 2014
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