DARK MATTER DECAY AND THE TEMPERATURE OF LYMAN-ALPHA CLOUDS

The recent discovery by Pettini et al. that Lyman-alpha clouds have low temperatures led them to derive an implausibly extreme model for the clouds. We here point out that a normal model could be retained if most of the photons ionizing the hydrogen in the cloud have an energy only a few percent greater than the ionization potential of hydrogen. Precisely this situation holds for the photons occuring in our decaying dark matter hypothesis, which would also account for the intensity of the required photon flux. This explanation implies that the proximity effect is not due to excess radiation from the nearby QSO. The significance of this conclusion is discussed.