Metallicities and Abundance Ratios from Quasar Broad Emission Lines

摘要: The broad emission lines (BELs) of quasars and active galactic nuclei (AGNs) are important diagnostics the relative abundances overall metallicity in gas. Here we present new theoretical predictions for several UV BELs. We focus specifically on nitrogen abundance as a indicator, based expected secondary enrichment at metallicities Z 0.2 Z☉. Among consider, N III] λ1750/O λ1664, V λ1240/(C IV λ1549 + O VI λ1034), V/He II λ1640 most robust diagnostics. argue, particular, that average BEL is not dominated by scattered Lyα photons from absorption-line wind. then compare our calculated line ratios with observations literature. results support earlier claims gas-phase near typically or times above solar value. conclude quasar activity preceded by, coeval with, an episode rapid extensive star formation surrounding (or protogalactic) nuclei. Chemical evolution models these environments suggest that, to reach Z☉ well-mixed interstellar gas, must have begun 108 yr before observed activity.