Dark matter plays role in galaxy formation

The creation of a starburst galaxy, says study co-author Asantha Cooray of the University of California, Irvine, is all a matter of blob size. If your blob is too big, hydrogen gas can't fall together efficiently enough to sustain a starmaking frenzy. Instead the gas breaks apart to make several separate, reasonably sedate galaxies. If the dark-matter blob is too small, by contrast, the hydrogen falls together too efficiently. Stars form so quickly and so furiously that their heat keeps the rest of hydrogen from falling in. The frenzy is short-lived.