We estimate the metallicity in the broad emission-line region of the redshift z = 4.16 quasar , BR2248-1242 , by comparing line ratios involving nitrogen to theoretical predictions .
BR2248-1242 has unusually narrow emission lines with large equivalent widths , thus providing a rare opportunity to measure several line-ratio abundance diagnostics .
The combined diagnostics indicate a metallicity of \sim 2 times solar .
This result suggests that an episode of vigorous star formation occurred near BR2248-1242 prior to the observed z = 4.16 epoch .
The time available for this enrichment episode is only \sim 1.5 Gyr at z = 4.16 ( for H _ { 0 } = 65 km s ^ { -1 } Mpc ^ { -1 } , \Omega _ { m } = 0.3 and \Omega _ { \Lambda } \lesssim 1 ) .
This evidence for high metallicities and rapid star formation is consistent with the expected early-epoch evolution of dense galactic nuclei .