Thick disks in other spiral galaxies

Spiral galaxies all appear to have two disk components: (1) the thin disk with its spiral structure, in which star formation has typically been going on for the last 10 Gyr, and (2) a thicker less massive thick disk component which  is usually very old and not forming stars now. We do not know yet how  this thick disk fits into the overall picture of galaxy formation. There are many possible mechanisms for forming thick disks - some involve the accretion and destruction of small companion galaxies.

If accreted galaxies do have a role in generating thick disks, then we might sometimes find that the thick and thin disks are rotating inopposite directions. Two papers by Yoachim and Dalcanton (2005, 2008) address this possibility: they measured the rotation of thick and thin disks in a small sample of galaxies and found one in which the rotation of the thin and thick disk could be in opposite directions. The observations are quite difficult and the outcome is not very secure: they need to be redone independently.

The WiFeS IFU spectrometer on The Australian National University 2.3-m telescope is well suited to this kind of observation (it is still difficult). In this proposed MSc project, we would observe the rotations in an independent sample of spiral galaxies.  The outcome is potentially important for determining theviability of the various proposed mechanisms for forming thick disks.

Additional supervision and networking with senior international collegues will be a part of the project