We present the results of a Suzaku study of the Arches cluster in the Galactic center region .
A high signal-to-noise ratio spectrum in the 3–12 keV band was obtained with the XIS ( X-ray Imaging Spectrometer ) onboard the Suzaku Observatory .
We found that the spectrum consists of a thermal plasma , a hard power-law tail , and two Gaussian line components .
The plasma component with a temperature of \sim 2.2 keV is established from the presence of Ca \emissiontype XIX and Fe \emissiontype XXV K \alpha lines as well as the absence of Fe \emissiontype XXVI K \alpha line .
The two Gaussian lines represent the K \alpha and K \beta lines from iron at lower ionization stages at \sim 6.4 and \sim 7.1 keV .
Both the line centers and the intensity ratio of these two lines are consistent with the neutral iron .
The hard power-law tail with a photon index of \sim 0.7 was found to have no pronounced iron K edge feature .
In comparison with the published Chandra spectra constructed separately for point-like and diffuse emission , we conclude that the thermal component is from the ensemble of point-like sources plus thermal diffuse emission concentrated at the cluster center , while the Gaussian and the hard tail components are from the non-thermal diffuse emission extended in a larger scale .
In the band-limited images of the XIS field , the distribution of the 7.5–10.0 keV emission resembles that of the 6.4 keV emission , including the local excess at the Arches cluster .
This strongly suggests that the power-law emission is related to the 6.4 and 7.1 keV lines in the underlying physics .
We discuss two ideas to explain both the hard continuum and the lines : ( 1 ) X-ray photoionization that produces fluorescence lines and the Thomson scattering continuum and ( 2 ) non-thermal electron impact ionization of iron atoms and bremsstrahlung continuum .
But whichever scenario is adopted , the photon or particle flux from the Arches cluster is too low to account for the observed line and continuum intensity .