The metallicity of the redshift 4.16 Quasar BR 2248-1242

We estimate the metallicity in the broad emission line region of the redshift z = 4.16 quasar BR 2248-1242 by comparing line ratios involving nitrogen to theoretical predictions. BR 2248-1242 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 ∼2 times solar. This result suggests that an episode of vigorous star formation occurred near BR 2248-1242 prior to the observed z = 4.16 epoch. The time available for this enrichment episode is only ∼1.5 Gyr at z = 4.16 (for H₀ = 65 km s^-1 Mpc ^-1, Ω_m = 0.3, and Ω_Λ ≲ 1). This evidence for high metallicities and rapid star formation is consistent with the expected early-epoch evolution of dense galactic nuclei.