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The Fermi Large Area Telescope (LAT) has recently detected a population ofglobular clusters (GCs) in high-energy (HE) gamma-rays. Their spectralproperties and energetics are consistent with cumulative emission from apopulation of millisecond pulsars (MSPs) hosted by these clusters. For example,the HE spectra exhibit fairly hard power-law indices and cutoffs around a fewGeV, typical of pulsed spectra measured for the gamma-ray pulsar population.The energetics may be used to constrain the number of visible MSPs in thecluster (N_vis), assuming canonical values for the average gamma-ray efficiencyand spin-down power. This interpretation is indeed strengthened by the factthat the first gamma-ray MSP has now been identified in the GC NGC 6624, andthis MSP is responsible for almost all of the HE emission from this cluster. Onthe other hand, it has been argued that the MSPs are also sources ofrelativistic leptons which may be reaccelerated in shocks originating incollisions of stellar winds in the cluster core, and may upscatter brightstarlight and cosmic microwave background photons to very high energies.Therefore, this unpulsed component may give an independent constraint on thetotal number of MSPs (N_tot) hosted in the GC, for a given cluster magneticfield B and diffusion coefficient k_0. Lastly, the transport properties of theenergetic leptons may be further constrained using multiwavelength data, e.g.,to infer the radial dependence of k_0 and B. We present results on our modelingof the pulsed and unpulsed gamma-ray fluxes from the GC Terzan 5.

Modeling High-energy and Very-high-energy gamma-rays from the Terzan 5 Cluster