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We report on 293 quasars with strong NIV] lambda 1486 or NIII] lambda 1750emission lines (rest-frame equivalent width > 3 \AA) at 1.7 < z < 4.0 selectedfrom the Sloan Digital Sky Survey (SDSS) Fifth Data Release. Thesenitrogen-rich (N-rich) objects comprise ~1.1% of the SDSS quasars. Thecomparison between the N-rich quasars and other quasars shows that the twoquasar subsets share many common properties. We also confirm previous resultsthat N-rich quasars have much stronger Lya and NV lambda 1240 emission lines.Strong nitrogen emission in all ionization states indicates high overallnitrogen abundances in these objects. We find evidence that the nitrogenabundance is closely related to quasar radio properties. The radio-loudfraction in the NIII]-rich quasars is 26% and in the NIV]-rich quasars is 69%,significantly higher than ~8% measured in other quasars with similar redshiftand luminosity. Therefore, the high nitrogen abundance in N-rich quasars couldbe an indicator of a special quasar evolution stage, in which the radioactivity is also strong.

A Sample of Quasars with Strong Nitrogen Emission Lines from the Sloan Digital Sky Survey