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

Thesis Supervisor: Magda Arnaboldi

Abstract

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 analysing a sample of several thousand planetary nebulae in order to separate the thin disk, thick disk and stellar halo in M31, which the goals of mapping the kinematics and the chemistry of the different components. We study the disk in M3 to see whether its thin and thick disk components 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. We wish to learn about 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 provided by computational groups based in the nearby institutes.

figure1_arnaboldi3

Figure 1: The several thousand PNe identified by the CFHT survey (Bhattacharya et al. 2019 A&A, 624, 132; blue - PNe with m5007 brighter than 25.64 mag, green - PNe with m5007fainter than 25:64 mag and photometric depth varying with pointings) are overlaid on the map of RGB stars identified by the PAndAS survey. The Merrett+06 PNe re-identified by the CFHT survey are shown in yellow. The main M31 disk and the known substructures within the survey area are marked. The white circle shows the MMT Hectospec multi-fiber wide field spectrograph, currently being used to acquire spectra for the CFHT PN sample. These spectra provide the line-of-sight velocity information and the oxygen abundance of the stars.