The Formation and Evolution of Tidal Tails

In this project we investigate the formation and evolution of tidal tails.

Tidal tails are produced if star clusters and dwarf galaxies are orbiting a larger object like the Milky Way. Stars of the smaller object become unbound but do not vanish from the object but orbit the MW on slightly different orbits producing a leading and a trailing tidal tail.

These tails can become very large, can show multiple arms and over-densities along their extend. These over-densities form naturally from the fact that the unbound stars in the tails are moving on epicycles around the MW.

Investigating these tails can give us insights about the initial mass of the small object and its orbit around the MW, as well as, if we have sufficient data from many objects, measures for the total enclosed mass of the MW and its potential.

We have develloped a code with which we can reliably measure the extend of the tails and the density along of them. We can recover the location and extension of the over-densities accurately.

We have shown that the standard epicyclic theory underpredicts the location of the first over-density and we have established a clear relation between the size and the distance of the first over-density in both tails (leading and trailing) seperately. Unluckily our relations are not able to distinguish between the influences of the orbit (i.e. the enclosed mass of the MW) and the mass of the satellite.

This work is/was supported by the following grants:

• FONDECYT regular No.1095092 and No. 1130521; PI: Michael Fellhauer
• BASAL: CATA