Extended Data Fig. 9: Illustration of Continuum Photon Pumping Process.
From: Extensive diffuse Lyman-α emission correlated with cosmic structure
a. With a single illumination source, IGM cloud absorbs in Lyα for observer A, and emits due to resonance scattering in the Lyα into the field of view of observer B. b. With a distribution of line and continuum illumination sources, observer A again sees absorption, which observer B, with illuminating sources resolved and therefore no illuminating sources in the field of view, sees an emission line. c. With a large number of faint illuminating sources, sufficiently numerous that they occupy the B field of view with the average metagalactic surface brightness, the absorption from the cloud exactly compensates for the scattered emission, and no line is observed. d. With a diffuse, uniform source of line and continuum emission the emission and absorption exactly cancel. In this paper, the scenario in panel b. pertains since the majority of the illuminating sources are resolved out and excluded from the emission measurement.
