Research WP6

Structure components of disk galaxies

The S4G mid-IR images provide an ideal database to study galaxy morphology and how it is related to secular evolution of galaxies. In this project the origin of early-type galaxies is studied. When the PhD projects starts, detailed morphological classifications will be available, at a similar level of detail as in Laurikainen et al. (2011, astro-ph/1110.1996). The S4G data analysis pipelines offer bulge/disk/bar decompositions which, together with the classifications, are used as a starting point for in-depth analysis of the structure components. The analysis methods include the Fourier amplitude and force calculation methods developed and extensively used by our group. The morphological properties are connected to stellar populations and kinematics of structures, in collaboration with IAC (where the student will spend an extended time period), and with Max Planck institute (MPIA). The scientific questions to be addressed are: (1) what are the possible progenitors of S0s (from dwarf S0s to bright SOs) in the nearby Universe,(2) to test the various bulge formation scenarios of S0s.

Signatures of secular evolution

Bar pattern speed $\omega_p$ is the main kinematic parameter of the bar, and it needs to be understood in any discussion of bar-related secular evolution of galaxies.  Current theoretical models predict that bars slow down by losing angular momentum to massive dark matter halo, which is not easy to reconcile with the fact that most observed bars are fast. One possible solution is that galaxies have maxima disks (implying insignificant halo contribution in the disk area), which in turn is not favored by current cosmological simulations. Interestingly, there is evidence that late-type galaxies have slower bars. Using the S4G data, (1) sticky particle simulation method (Salo et al. 1999, AJ, 117, 792) is used to estimate $\Omega_p$, for the first time for a significant galaxy sample covering all morphological types. (2) For a sub-sample of galaxies, detailed fully self-consistant N-body simulations can also be analyzed.