Emission from the z = 2 damped Lyα absorber toward Q1215 + 333

We have detected narrow emission lines at 1.118 μm and 1.456 μm in the spectrum of the z = 2.606 quasar Q1215 + 333, corresponding to [O II] λ3727 and Hβ at z = 1.9984, the redshift of a damped Lyα absorber toward this quasar. The intensity of the Hβ line is 7.6 ± 2 × 10^-16 ergs cm^-2 s^-1, which corresponds to a line luminosity of 5 × 10⁴² ergs s^-1 h^-2₁₀₀ (q₀ = 0.5). If we assume that the photoionization producing the emission is due purely to massive star formation with a Salpeter initial mass function, we find a total star formation rate of 100 M_⊙ yr^-1 h^-2₁₀₀. Given the uncertainty in the initial mass function and cosmological parameters, this star formation rate is very uncertain. However, the star formation rate is well above those inferred from Lyα emission-line searches of similar systems, implying effective destruction of Lyα photons. The intensity of the [O II] λ3727 line is 1.6 ± 0.3 × 10^-15 ergs cm^-2 s^-1. The ratio [O II]/Hβ ≈ 2 and the weakness of the ratio [O III] λ5007/β < 0.5 is typical of star formation regions with gas at nearly solar metallicity.