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An overview of active galaxies

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Figure 29
Figure 29 (a) The faint red source indicated by the arrow is a quasar with redshift z = 6.2. (b) Spectra of three very distant quasars. In each case the highest observed flux is the Lyα emission line, which has been redshifted into the red part of the optical spectrum. To shorter wavelengths the detected flux is zero because all these photons have undergone Lyman absorption by less redshifted neutral hydrogen gas between us and the quasar

 8.6 Line spectra: Activity 8 Quasar redshifts