Parameterization of the Angular Distribution of Gamma Rays Produced by p-p Interaction in Astronomical Environment

We present the angular distribution of gamma rays produced by proton-proton interactions in parameterized formulae to facilitate calculations in astrophysical environments. The parameterization is derived from Monte Carlo simulations of the up-to-date proton-proton interaction model by Kamae et al. (2005) and its extension by Kamae et al. (2006). This model includes the logarithmically rising inelastic cross section, the diffraction dissociation process and Feynman scaling violation. The extension adds two baryon resonance contributions: one representing the Delta(1232) and the other representing multiple resonances around 1600 MeV/c^2. We demonstrate the use of the formulae by calculating the predicted gamma-ray spectrum for two different cases: the first is a pencil beam of protons following a power law and the second is a fanned proton jet with a Gaussian intensity profile impinging on the surrounding material. In both cases we find that the predicted gamma-ray spectrum to be dependent on the viewing angle.Comment: 8 pages, 7 figures, figure 7 updated, accepted for publication in ApJ, text updated to match changes by the editor, two refs updated from preprints to full journal

Experimental study of the stability and flow characteristics of floating liquid columns confined between rotating disks

A low Bond number simulation technique was used to establish the stability limits of cylindrical and conical floating liquid columns under conditions of isorotation, equal counter rotation, rotation of one end only, and parallel axis offset. The conditions for resonance in cylindrical liquid columns perturbed by axial, sinusoidal vibration of one end face are also reported. All tests were carried out under isothermal conditions with water and silicone fluids of various viscosities. A technique for the quantitative measurement of stream velocity within a floating, isothermal, liquid column confined between rotatable disks was developed. In the measurement, small, light scattering particles were used as streamline markers in common arrangement, but the capability of the measurement was extended by use of stereopair photography system to provide quantitative data. Results of velocity measurements made under a few selected conditions, which established the precision and accuracy of the technique, are given. The general qualitative features of the isothermal flow patterns under various conditions of end face rotation resulting from both still photography and motion pictures are presented

Inverse Compton Emission from Galactic Supernova Remnants: Effect of the Interstellar Radiation Field

The evidence for particle acceleration in supernova shells comes from electrons whose synchrotron emission is observed in radio and X-rays. Recent observations by the HESS instrument reveal that supernova remnants also emit TeV gamma-rays; long awaited experimental evidence that supernova remnants can accelerate cosmic rays up to the ``knee'' energies. Still, uncertainty exists whether these gamma-rays are produced by electrons via inverse Compton scattering or by protons via neutral pion decay. The multi-wavelength spectra of supernova remnants can be fitted with both mechanisms, although a preference is often given to neutral pion decay due to the spectral shape at very high energies. A recent study of the interstellar radiation field indicates that its energy density, especially in the inner Galaxy, is higher than previously thought. In this paper we evaluate the effect of the interstellar radiation field on the inverse Compton emission of electrons accelerated in a supernova remnant located at different distances from the Galactic Centre. We show that contribution of optical and infra-red photons to the inverse Compton emission may exceed the contribution of cosmic microwave background and in some cases broaden the resulted gamma-ray spectrum. Additionally, we show that if a supernova remnant is located close to the Galactic Centre its gamma-ray spectrum will exhibit a ``universal'' cutoff at very high energies due to the Klein-Nishina effect and not due to the cut-off of the electron spectrum. As an example, we apply our calculations to the supernova remnants RX J1713.7-3946 and G0.9+0.1 recently observed by HESS.Comment: 4 pages, 4 figures. Uses emulateapj.cls. Accepted by ApJ