Galaxy counterparts of metal-rich damped Lyα absorbers – I. The case of the z= 2.35 DLA towards Q 2222−0946

We have initiated a survey using the newly commissioned X-shooter spectrograph to target candidate relatively metal-rich damped Lyα absorbers (DLAs). Our rationale is that highmetallicity DLAs due to the luminosity–metallicity relation likely will have the most luminous galaxy counterparts. In addition, the spectral coverage of X-shooter allows us to search for not only Lyα emission, but also rest-frame optical emission lines. We have chosen DLAs where the strongest rest-frame optical lines ([O II], [O III], Hβ and Hα) fall in the nearinfrared atmospheric transmission bands. In this first paper resulting from the survey, we report on the discovery of the galaxy counterpart of the zabs = 2.354 DLA towards the z = 2.926 quasar Q 2222−0946. This DLA is amongst the most metal-rich z > 2 DLAs studied so far at comparable redshifts and there is evidence for substantial depletion of refractory elements on to dust grains. We measure metallicities from Zn II ,S iII ,N iII ,M nII and Fe II of −0.46 ± 0.07, −0.51 ± 0.06, −0.85 ± 0.06, −1.23 ± 0.06 and −0.99 ± 0.06, respectively. The galaxy is detected in the Lyα ,[ OIII] λλ4959, 5007 and Hα emission lines at an impact parameter of about 0.8 arcsec (6 kpc at zabs = 2.354). Based on the Hα line, we infer a