Open clusters are gravitationally-bound groups of stars, that are found in the disks of spiral galaxies. Under the influence of the galactic gravitational potential clusters lose stars, which form structures called tidal tails. The shapes of tidal tails therefore depend on the galactic gravitational potential. While the motion of stars in the tidal tails can be described analytically in axially symmetric potentials, n-body simulations are needed for tracking the formation of tidal tails in general potentials. The Milky Way hosts a central bar, an elongated rotating structure, which causes deviations from an axially symmetric potential and affects stellar orbits even at large distances from the galactic centre. One of the key parameters of the bar's gravitational potential is the its rotation rate, called the pattern speed. Despite extensive research, the value of the pattern speed is still under debate. In this master's thesis we examine the influence of the bar on the shapes of tidal tails of open clusters in the Solar neighbourhood. We track the formation of tidal tails of selected clusters through n-body simulations, while varying the pattern speed. We analyse the results of the simulations using statistical distance metrics: Kullback-Leibler divergence and Maximum Mean Discrepancy (MMD), which provide us with a measurement of similarity between simulations of the same cluster. We show that the shapes of tidal tails of open clusters are strongly influenced by the bar. Using the calculated statistical distances we determine which clusters are most sensitive to changes of the pattern speed. Considering the results, we conclude that by observing tidal tails of open clusters we could be able to determine the pattern speed with a precision of the order of 1 kms$^{-1}$kpc$^{-1}$. We expect that the needed observations will be available in the Gaia mission's fourth data release.
|
