So far, six mechanisms have been proposed to account for the Galactic disk heating. Of these, the most important appear to be a combination of scattering of stars by molecular clouds and by spiral arms. We study a further mechanism, namely, the repeated disk impact of the original Galactic Globular Cluster population up to the present. We find that Globular Clusters could have contributed at most a small fraction of the current vertical energy of the disk, as they could heat the whole disk to { $\sigma $}$_{ z}$ = 5.5kms$^{ { \rm -} { \rm 1}}$ (c.f. the observed 18 and 39 kms$^{ { \rm -} { \rm 1}}$ for the thick and thin disks respectively). We find that the rate of rise of disk heat ($\alpha$=0.22 in \textit{ $\sigma $}$_{ z}$ $\sim t^{ \alpha}$ with \textit t being time), is close to that found for scattering by molecular clouds.
Categories: astro-ph.GA