The Evolution of X { ray selected Narrow Emission LineGalaxiesM

We examine the cosmological evolution of X{ray selected narrow emission line galaxies (NELGs), using a sample of 35 such objects identiied in the combined ROSAT UK Deep survey and RIXOS. This sample is entirely independent of those previously used to investigate the X{ray evolution of NELGs. We detect evolution which is at a similar rate to the evolution found in the optical luminosity function of blue galaxies. The lack of high redshift (z > 0:6) NELGs detected in X{ray surveys, and the small, well deened number of X{ray sources which are not optically identiied, indicate that the evolution of NELGs is probably not the same as the X{ray evolution of QSOs: NELG evolution is slower than the evolution of QSOs and/or ends at a lower redshift.