Detalles de publicación
PP 014148
Dissecting galactic bulges in space and time I: the importance of early formation scenarios vs. secular evolution
1Instituto de Astrofísica de Canarias, E-38200 La Laguna, Tenerife, Spain
2Departamento de Astrofísica, Universidad de La Laguna, E-38205 La Laguna, Tenerife, Spain
3Dpto. de Astrofísica y CC. de la Atmósfera, Universidad Complutense de Madrid, Spain
4Dpto. de Física Teórica y del Cosmos, Universidad de Granada, Facultad de Ciencias (Edificio Mecenas), 18071 Granada, Spain 5Instituto Universitario Carlos I de Física Teórica y Computacional, Universidad de Granada, 18071 Granada, Spain
6Dpto. de Física Teórica, Universidad Autónoma de Madrid, E-28049 Cantoblanco, Spain
7Research School of Astronomy and Astrophysics, Australian National University, Canberra, ACT 2611, Australia 8Max-Planck-Institut für Astronomie, Königstuhl 17, D-69117 Heidelberg, Germany
9European Southern Observatory, Karl-Schwarzschild-Str. 2, 85748 Garching, Germany
The details of bulge formation via collapse, mergers, secular processes or their interplay re- main unresolved. To start answering this question and quantify the importance of distinct mechanisms, we mapped a sample of three galactic bulges using data from the integral field spectrograph WiFeS on the ANU 2.3m telescope in Siding Spring Observatory. Its high resolu- tion gratings (R∼7000) allow us to present a detailed kinematic and stellar population analysis of their inner structures with classical and novel techniques. The comparison of those tech- niques calls for the necessity of inversion algorithms in order to understand complex substruc- tures and separate populations. We use line-strength indices to derive SSP-equivalent ages and metallicities. Additionally, we use full spectral fitting methods, here the code STECKMAP, to extract their star formation histories. The high quality of our data allows us to study the 2D distribution of different stellar populations (i.e. young, intermediate, and old). We can identify their dominant populations based on these age-discriminated 2D light and mass contribution. In all galactic bulges studied, at least 50% of the stellar mass already existed 12 Gyrs ago, more than currently predicted by simulations. A younger component (age between ∼1 to ∼8 Gyrs) is also prominent and its present day distribution seems to be affected much more strongly by morphological structures, especially bars, than the older one. This in-depth analysis of the three bulges supports the notion of increasing complexity in their evolution, likely to be found in numerous bulge structures if studied at this level of detail, which cannot be achieved by mergers alone and require a non-negligible contribution of secular evolution.