Answer to Question #89475 in Astronomy | Astrophysics for sandra

Question

What is the difference between the density-bounded medium and the picket fence model?

Answer 1

Lyman continuum radiation can be allowed to escape a galaxy mainly by two means. In one scenario, the source region scan be surrounded by a largely isotropic gas with a sufficiently low column density of neutral hydrogen N_HI to not completely attenuate the passing Lyman-continuum radiation. This is usually referred to as the density-bounded medium. In a second scenario, the neutral medium is optically thick, but does not completely cover the ionizing sources. This scenario has been referred to as the picket fence model,or the ionization-bounded medium with holes.