ABSTRACT
The Milky Way is known to be an abundant source of gamma-ray photons, now determined to be mainly diffuse in nature and resulting from interstellar processes. In the soft gamma-ray domain, point sources are expected to dominate, but the lack of sensitive high-resolution observations did not allow for a clear estimate of the contribution from such sources. Even the best imaging experiment revealed only a few point sources, accounting for about 50% of the total Galactic flux. Theoretical studies were unable to explain the remaining intense diffuse emission. Investigating the origin of the soft gamma-rays is therefore necessary to determine the dominant particle acceleration processes and to gain insights into the physical and chemical equilibrium of the interstellar medium. Here we report observations in the soft gamma-ray domain that reveal numerous compact sources. We show that these sources account for the entirety of the Milky Way's emission in soft gamma-rays, leaving at most a minor role for diffuse processes.
ABSTRACT
A hard x-ray/medium energy gamma-ray telescope is being developed using coded-aperture imaging. The image recorded on the detector has to be cross correlated to deconvolve the sky map. This map suffers from blurring due to the spatial resolution of the position sensitive detector and to the simple point spread function of the cross-correlation method. We have developed and tested an iterative method which improves the separating power of the reconstructed maps. The results and limits of the method are discussed.
ABSTRACT
A hard x-ray/medium energy gamma-ray telescope is being developed using coded aperture imaging. The image recorded on the detector has to be cross correlated to deconvolve the sky map. We have developed a deconvolution method using the 2-D discrete Fourier transform, whose goal is to improve the separating power of these reconstructed maps. The results and limits of the method are discussed.
ABSTRACT
Coded mask aperture imaging techniques are now used in various fields, in particular in x-ray and gamma-ray astronomy. With such systems it is possible to construct apertures which have autocorrelation functions with perfectly flat sidelobes. For quadratic residue arrays (uniformly redundant arrays-URAs), we have developed fast deconvolution algorithms based on conventional decoding methods but taking advantage of the mathematical properties of the decoding matrices. Balanced decoding, delta decoding, and finely sampled decoding are discussed.
