A SINFONI integral field spectroscopy survey for galaxy counterparts to damped Lyman α systems - I. New detections and limits for intervening and associated absorbers

Detailed studies of damped and sub-damped Lyman α systems (DLAs), the galaxies probed by the absorption they produce in the spectra of background quasars, rely on identifying the galaxy responsible for the absorber with more traditional methods. Integral field spectroscopy provides an efficient way of detecting faint galaxies near bright quasars, further providing immediate redshift confirmation. Here, we report the detection of Hα emission from a DLA and a sub-DLA galaxy among a sample of six intervening quasar absorbers targeted. We derive F(Hα) = 7.7 ± 2.7 × 10^-17 erg s^-1 cm^-2 (SFR = 1.8 ± 0.6 M_⊙ yr^-1) at impact parameter b= 25 kpc towards quasar Q0302 - 223 for the DLA at z_abs= 1.009 and F(Hα) = 17.1 ± 6.0 × 10^-17 erg s^-1 cm^-2 (SFR = 2.9 ± 1.0 M_⊙ yr^-1) at b= 39 kpc towards Q1009 - 0026 for the sub-DLA at z_abs= 0.887. These results are in line with low star formation rates previously reported in the literature for quasar absorbers. We use the [N II]λ 6585/Hα ratio to derive the H II emission metallicities and compare them with the neutral gas H I absorption metallicities derived from high-resolution spectra. In one case, the absorption metallicity is actually found to be higher than the emission line metallicity. For the remaining objects, we achieve 3σ limiting fluxes of the order F(Hα) ∼ 10^-17 erg s^-1 cm^-2 (corresponding to SFR ∼ 0.1 M_⊙ yr^-1 at z∼ 1 and ∼1 M_⊙ yr^-1 at z∼ 2), i.e. among the lowest that have been possible with ground-based observations. We also present two other galaxies associated with C IV systems and serendipitously discovered in our data. Based on observations collected during programmes ESO 79.A-0673 and 80.A-0742 at the European Southern Observatory with SINFONI on the 8.2-m YEPUN telescope operated at the Paranal Observatory, Chile.