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Recent claims of a gamma-ray excess in the diffuse galactic emission detectedby the Fermi Large Area Telescope with a morphology similar to the WMAP hazewere based on the assumption that spatial templates of the interstellar medium(ISM) column density and the 408 Mhz sky are good proxies for neutral pion andinverse Compton (IC) gamma-ray emission, respectively. We identify significantsystematic effects in this procedure that can artificially induce an additionaldiffuse component with a morphology strikingly similar to the claimed gamma-rayhaze. To quantitatively illustrate this point we calculate sky-maps of theratio of the gamma-ray emission from neutral pions to the ISM column density,and of IC to synchrotron emission, using detailed galactic cosmic-ray modelsand simulations. In the region above and below the galactic center, the ISMtemplate underestimates the gamma-ray emission due to neutral pion decay byapproximately 20%. Additionally, the synchrotron template tends tounder-estimate the IC emission at low energies (few GeV) and to over-estimateit at higher energies (tens of GeV) by potentially large factors that dependcrucially on the assumed magnetic field structure of the Galaxy. The size ofthe systematic effects we find are comparable to the size of the claimed "Fermihaze" signal. We thus conclude that a detailed model for the galactic diffuseemission is necessary in order to conclusively assess the presence of agamma-ray excess possibly associated to the WMAP haze morphology.

Systematic Effects in Extracting a "Gamma-Ray Haze" from Spatial Templates