The spatial distribution of metals in disc galaxies, via simulations and observations

Abstract

In this thesis we are interested in the evoluNon of disc galaxies. One of the most common ways to study it is by a deep analysis of the distribuNon of chemical abundances in the stellar populaNons of the disc component. Abundance gradients let us reconstruct the puzzle of the formaNon and evoluNon of this type of galaxies, once we learn about the different elements that are released to the interstellar medium at each stage of the life of stars.
In this work we pay special aaenNon to the so-­‐called thick disc component of spiral galaxies, believing that it is a relic of the early galaxy and its understanding opens the door for a complete galaxy formaNon scenario. We analyse thick discs both with observaNonal data and simulaNons because we want to have a wider view of the situaNon and we think that such complementary approaches can help us maximise our knowledge and results.
Our simulaNons with an enhanced feedback are the ones that best reproduce the measured data from the Milky Way. The trend for the variaNon of the mean metallicity with galacNc radius at different heights from the plane matches that in the Galaxy. It is negaNve in the mid-­‐plane of galaxies and then becomes posiNve at greatest heights. According to simulaNons, this behaviour is due to a populaNon of relaNvely young and metal-­‐rich stars formed in situ in the outer galaxy, which is missing in the inner thick disc.
When looking at the same magnitudes but via observaNons from the CALIFA local universe galaxy sample, we see that the external galaxies exhibit a variety of different behaviours both for the metallicity and age radial gradients with height, in addiNon to the trend found in simulaNons and the Milky Way. We deduce that thick discs probably do not form through a unique mechanism but from a combinaNon of many of them.
Finally we want to know the influence of the galacNc mass in the chemical evoluNon of a disc galaxy. By using a fiducial set of simulaNons and comparing the results to observaNonal data we conclude that the smallest systems in our set might have an incorrect feedback efficiency, and suggest that a mass-­‐dependent modulaNon of feedback might improve the result.