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The Milky Way provides an ideal laboratory to test our understanding of galaxy evolution, owing to our ability to observe our Galaxy over fine scales. However, connecting the Galaxy to the wider galaxy population remains difficult, due to the challenges posed by our internal perspective and to the different observational techniques employed. Here, we present a sample of galaxies identified as Milky Way analogues on the basis of their stellar masses and bulge-to-total ratios, observed as part of the Mapping Nearby Galaxies at Apache Point Observatory survey. We analyse the galaxies in terms of their stellar kinematics and populations as well as their ionized gas contents. We find our sample to contain generally young stellar populations in their outskirts. However, we find a wide range of stellar ages in their central regions, and we detect central active galactic nucleus-like or composite-like activity in roughly half of the sample galaxies, with the other half consisting of galaxies with central star-forming emission or emission consistent with old stars. We measure gradients in gas metallicity and stellar metallicity that are generally flatter in physical units than those measured for the Milky Way; however, we find far better agreement with the Milky Way when scaling gradients by galaxies' disc scale lengths. From this, we argue much of the discrepancy in metallicity gradients to be due to the relative compactness of the Milky Way, with differences in observing perspective also likely to be a factor. [ABSTRACT FROM AUTHOR]

The main goal of Galactic Archaeology is to understand the formation and evolution of the basic Galactic components. This requires sophisticated chemo-dynamical modeling, where disk asymmetries (e.g., perturbations from the bar, spirals, and mergers) and nonequilibrium processes are taken into account self-consistently. Here we discuss the current status of Galactic chemo-dynamical modeling and focus on a recent hybrid technique, which helps circumvent traditional problems with chemical enrichment and star formation encountered in fully self-consistent cosmological simulations. We show that this model can account for a number of chemo-kinematic relations in the Milky Way, as discussed in previous works. In addition, we demonstrate that our model matches well the observed age-[c*/Fe] relation and that blurring may be insufficient to explain the scatter in the age-metallicity relation. [ABSTRACT FROM AUTHOR]

In the first paper of this series (Paper I) we presented a new approach for studying the chemodynamical evolution in disk galaxies, focusing on the Milky Way. While in Paper I we studied extensively the Solar vicinity, here we extend these results to different distances from the Galactic center, looking for variations of observables that can be related to on-going and future spectroscopic surveys. By separating the effects of kinematic heating and radial migration, we show that migration is much more important, even for the oldest and hottest stellar population. The distributions of stellar birth guiding radii and final guiding radii (signifying contamination from migration and heating, respectively) widen with increasing distance from the Galactic center. As a result, the slope in the agemetallicity relation flattens significantly at Galactic radii larger than solar. We predict that the metallicity distributions of (unbiased) samples at different distances from the Galactic center peak at approximately the same value, [Fe/H] ≈ -0.15 dex, and have similar metal-poor tails extending to [Fe/H] ≈ -1.3 dex. In contrast, the metal-rich tail decreases with increasing radius, thus giving rise to the expected decline of mean metallicity with radius. Similarly, the [Mg/Fe] distribution always peaks at ≈0.15 dex, but its low-end tail is lost as radius increases, while the high-end diminishes at [Mg/Fe] ≈ 0.45 dex. The radial metallicity and [Mg/Fe] gradients in our model show significant variations with height above the plane because of changes in the mixture of stellar ages. An inversion in the radial metallicity gradient is found from negative to weakly positive (at r < 10 kpc), and from positive to negative for the [Mg/Fe] gradient, with increasing distance from the disk plane. We relate this to the combined effect of (i) the predominance of young stars close to the disk plane and old stars away from it; (ii) the more concentrated older stellar component; and (iii) the flaring of mono-age disk populations. We also investigate the effect of recycled gas flows on the mean [Fe/H] and find that in the region 4 < r < 12 kpc the introduced errors are less than 0.05-0.1 dex, related to the fact that inward and outward flows mostly cancel in that radial range. We show that radial migration cannot compete with the inside-out formation of the disk, exposed by the more centrally concentrated older disk populations, and consistent with recent observations. [ABSTRACT FROM AUTHOR]