We have investigated the properties of a group of $\gamma$-ray emitting globular clusters (GCs) which have recently been uncovered in our Galaxy. By correlating the observed $\gamma$-ray luminosities $L_{ \gamma}$ with various cluster properties, we probe the origin of the high energy photons from these GCs. We report $L_{ \gamma}$ is positively correlated with the encounter rate $\Gamma_{ c}$ and the metalicity $\left[{ \rm Fe/H}\right]$ which place an intimate link between the gamma-ray emission and the millisecond pulsar population. We also find a tendency that $L_{ \gamma}$ increase with the energy densities of the soft photon at the cluster location. Furthermore, the two-dimensional regression analysis suggests that $L_{ \gamma}$, soft photon densities, and $\Gamma_{ c}$/$\left[{ \rm Fe/H}\right]$ possibly span fundamental planes which potentially provide better predictions for the $\gamma$-ray properties of GCs.
Categories: astro-ph.HE