Thesis topic: Disks, stellar halos, and disk-halo interface in the Andromeda galaxy (M31) resolved with planetary nebulae



Thesis Supervisor: Magda Arnaboldi





Andromeda (M31) is the nearest large spiral galaxy to our Milky Way. At mere 780 kpc distance it is an ideal target for studying such galaxies with individual stars. We are planning to analyze a sample of several thousands planetary nebulae in order to separate the thin disk, thick disk and stellar halo in M31. The goal is to see whether the thin and thick disks have similar or different structures from those in our Galaxy, and learn about their formations. M31 and the Milky Way are the only two large galaxies for which such comparative study is possible. In this thesis we will quantify the motions in the substructures in the stellar halo of M31 and the fraction of stars in the disk-halo interface. The goal is to understand the relative importance of accretion and in-situ processes in the formation of the stellar halo. This thesis requires active participation to the data reduction and analysis, and comparison between observations and the results from dynamical/cosmological simulations.


Figure 1: Left: Position - velocity diagram along the major axis of M31 for the PNe sample from Merrett et al. (2006). The highlighted objects are those in the region of satellite galaxies (circles; M32, NGC 205, Andromeda IV, etc); those in the region of the Northern Spur are indicated by squares and those identied as forming a continuation of the Southern Stream by triangles. Right: Position - velocity diagram for a sample of PNe extracted from an EAGLE M31-like-galaxy.