7 Appendix

During our survey for emission line galaxies we also identified a few quasars and AGNs. Here we give some spectroscopic information about a peculiar QSO found in our survey, namely HS 1643+5313. This object looked peculiar also in the objective-prism scans, in the sense that it displayed a double peaked feature, just at the green head

Figure 5: Slit spectrum of the quasar HS 1643+5313, z=0.785

of the objective prism spectrum. A first possibility would have been that the strongest feature were the [OIII]${\lambda}$5007 line of a narrow-emission line galaxy while the second feature a cosmic or only noise. No other combination of emission-lines at any redshift and at this dispersion were known to fit the above mentioned spectrum. The spectrum was therefore chosen mainly with the hope of being still a narrow-emission line galaxy. The slit spectrum (Fig. 5) displays the same combination of a double emission-line feature. After analysing in detail the spectrum as well as its direct image we reached the conclusion that the object is a QSO at z = 0.785, the emission-features being thus only one line, namely the MgII ${\lambda}{\lambda}$2798 blend,

but with an absorption dip inside. There is also some faint detection of FeII at 5262Å, but the S/N ratio of the spectrum is too poor for a clear detection of further fainter lines. A high resolution spectrum of the near infrared region would clarify whether the absorption is internal to the QSO or arises from a foreground cloud or galaxy.

Acknowledgements

U.H. acknowledges the support of the SFB 375. This research has made use of the NASA/IPAC Extragalactic Database (NED) which is operated by the Jet Propulsion Laboratory, California Institute of Technology, under contract with the National Aeronautics and Space Administration.