Published in "Galactic Bulges", Astrophysics and Space Science Library, Volume 418. ISBN 978-3-319-19377-9. Springer International Publishing Switzerland, 2016, p. 199.
http://arxiv.org/abs/1503.07252

For a PDF version of the article, click here.

THE MILKY WAY BULGE: OBSERVED PROPERTIES AND A COMPARISON TO EXTERNAL GALAXIES

Oscar A. Gonzalez and Dimitri A. Gadotti


European Southern Observatory, Alonso de Cordova 3107, Vitacura, Santiago, Chile


Abstract: The Milky Way bulge offers a unique opportunity to investigate in detail the role that different processes such as dynamical instabilities, hierarchical merging, and dissipational collapse may have played in the history of the Galaxy formation and evolution based on its resolved stellar population properties. Large observation programmes and surveys of the bulge are providing for the first time a look into the global view of the Milky Way bulge that can be compared with the bulges of other galaxies, and be used as a template for detailed comparison with models. The Milky Way has been shown to have a box/peanut (B/P) bulge and recent evidence seems to suggest the presence of an additional spheroidal component. In this review we summarise the global chemical abundances, kinematics and structural properties that allow us to disentangle these multiple components and provide constraints to understand their origin. The investigation of both detailed and global properties of the bulge now provide us with the opportunity to characterise the bulge as observed in models, and to place the mixed component bulge scenario in the general context of external galaxies. When writing this review, we considered the perspectives of researchers working with the Milky Way and researchers working with external galaxies. It is an attempt to approach both communities for a fruitful exchange of ideas.


Table of Contents

INTRODUCTION

THE STRUCTURE OF THE MILKY WAY BULGE

THE AGE OF THE MILKY WAY BULGE

THE CHEMICAL ABUNDANCES OF THE MILKY WAY BULGE
The metallicity distribution
The Bulge alpha-element abundances

THE BULGE KINEMATICS

THE MILKY WAY BULGE IN A NUTSHELL

THE MILKY WAY BULGE IN THE CONTEXT OF EXTERNAL GALAXIES
The X-shaped Bulge of the Milky Way: how rare is this?
Bulge formation scenarios
Bulges formed via disc instabilities
Bulges formed via violent processes
Composite bulges

CONCLUDING REMARKS

REFERENCES

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