THE INTRINSIC SHAPE OF GALAXY BULGES

by Mendez-Abreu et al. (To be published in Galactic Bulges, Springer)     [March, 2015]

The knowledge of the intrinsic three-dimensional (3D) structure of galaxy components provides crucial information about the physical processes driving their formation and evolution. In this paper I discuss the main developments and results in the quest to better understand the 3D shape of galaxy bulges. I start by establishing the basic geometrical description of the problem. Our understanding of the intrinsic shape of elliptical galaxies and galaxy discs is then presented in a historical context, in order to place the role that the 3D structure of bulges play in the broader picture of galaxy evolution. Our current view on the 3D shape of the Milky Way bulge and future prospects in the field are also depicted. Read More

Previously in News!

SECULAR- AND MERGER-BUILT BULGES IN BARRED GALAXIES

by Mendez-Abreu et al.   New article in A&A, 572, 25   [December, 2014]

The most popular models for bulge formation invokes a multi-phase evolution in which bulges can be formed at high-redshift by gravitational collapse, major mergers, or coalescence of giant clumps. Then, they evolve through secular evolution processes, either internal (bar or spiral arm induced), or external (minor mergers). Different evolutionary paths led to the different bulge types so it is likely that different bulges coexist within the same galaxy. In this new study we study the incidence, as well as the nature, of composite bulges in a sample of 10 face-on barred galaxies to constrain the formation and evolutionary processes of the central regions of disk galaxies. We find a high frequency (80%) of composite bulges in barred galaxies points towards a complex formation and evolutionary scenario. Moreover, the evidence for coexisting merger- and secular-built bulges reinforce this idea. We discuss how the presence of different bulge types, with different formation histories and timescales, can constrain current models of bulge formation. Read More