The detection of Lyα emission in star‐forming galaxies in different shapes and intensities (always smaller than predicted for case B recombination) has puzzled the astronomical community for more than a decade. Here we use two‐dimensional calculations to follow the evolution of superbubbles and of the H ii regions generated by the output of UV photons from massive stars. We show the impact caused by massive star formation in the ISM of different galaxies and we look at the conditions required to detect Lyα emission from a nuclear H ii region, and the variety of profiles that may be expected as a function of time.

A B S T R A C TTwo-dimensional calculations of the evolution of remnants generated by the strong mechanical energy deposited by stellar clusters in dwarf galaxies (M ϳ 10 9 -10 10 M ᭪ ) are presented. The evolution is followed for times longer than both the blowout time and the presumed span of energy injection generated by a coeval massive stellar cluster. The remnants are shown to end up wrapping around the central region of the host galaxy, while growing to kiloparsecscale dimensions. Properties of the remnants such as luminosity, size, swept-up mass and expansion speed are given as functions of time for all calculated cases.The final fate of the swept-up galactic gas and of the matter processed by the central starburst is shown to be highly dependent on the properties of the low-density galactic halo. Superbubbles powered by star clusters, with properties similar to those inferred from the observations, slow down in the presence of an extended halo to expansion speeds smaller than the host galaxy escape velocity. Values of the critical luminosity required for the superbubbles to reach the edge of the galaxies with a speed comparable to the escape speed are derived analytically and numerically. The critical luminosities are larger than those in the detected sources, and thus the superbubbles in amorphous dwarf galaxies must have already undergone blowout and are presently evolving into an extended low-density halo. This will inhibit the loss of the swept-up and processed matter from the galaxy.

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