1998ApJ...507L.113Y

The observed Fe II (UV+optical)/Mg II λλ2796, 2804 flux ratio from a gravitationally lensed quasar B1422+231 at z=3.62 is interpreted in terms of detailed modeling of photoionization and chemical enrichment in the broad-line region (BLR) of the host galaxy. The delayed iron enrichment by Type Ia supernovae is used as a cosmic clock. Our standard model, which matches the Fe II/Mg II ratio, requires the age of 1.5 Gyr for B1422+231 with a lower bound of 1.3 Gyr, which exceeds the expansion age of the Einstein-de Sitter Ω₀=1 universe at a redshift of 3.62 for any value of the Hubble constant in the currently accepted range, H₀=60-80 km.s^–1.Mpc^–1. This problem of an age discrepancy at z=3.62 can be unraveled in a low-density Ω₀≲0.2 universe, either with or without a cosmological constant, depending on the allowable redshift range of galaxy formation. However, whether the cosmological constant is a required option in modern cosmology awaits a thorough understanding of line transfer processes in the BLRs.