This model as reported by Paul Sutherland of SkyMania.
To quote Mr. Sutherland:
"The UCLan's breakthrough came after they included in their calculations a figure for the amount of energy released by exploding stars that was 10 to 100 times greater than any previously used. This at last gave them a galaxy that began to resemble the Milky Way. What previously appeared like a blob of stars, with a little disk inside it, slowly disappeared, to be replaced by the opposite. It was exactly what they wanted to find.
Dr [Chris] Brook said: "From our analysis we realised that all attempts were being far too conservative in their energy usage from very massive stars –- those 10 to 100 times more massive than the Sun. When massive stars ‘die' they explode spectacularly and return most of the chemical elements out of which us, our planet, and our solar system formed, as well as an enormous amount of energy into the surrounding gas. We decided to be more aggressive in our simulations of the energy released by both living and dying massive stars."