UM663-AN ILLUSTRATION OF THE CERENKOV REDSHIFT

In this paper, we point out that the spectrum of the quasar UM663 can not be explained by photoionization models; on the contrary, it can be explained by the theory of Cerenkov line radiation. The Cerenkov redshift Δλ_c( 24Å )of the emission line Lα of this quasar has been estimated from the position of Nv absorption line in the Lα-Nv profile.