Detection of emission lines from z ∼ 3 DLAs towards the QSO J2358+0149

Using VLT/X-shooter, we searched for emission line galaxies associated with four damped Lyman alpha systems (DLAs) and one sub-DLA at 2.73 a parts per thousand currency signz a parts per thousand currency sign3.25 towards QSO J2358+0149. We detect [O iii] emission from a 'low-cool' DLA at z(abs) = 2.9791 (having log N(H i) = 21.69 +/- 0.10, [Zn/H] = -1.83 +/- 0.18) at an impact parameter of, rho similar to 12 kpc. The associated galaxy is compact with a dynamical mass of (1-6) x 10(9) M-aS (TM), very high excitation ([O iii]/[O ii] and [O iii]/[H beta] both greater than 10), 12+[O/H]a parts per thousand currency sign8.5 and moderate star formation rate (SFR a parts per thousand currency sign2 M-aS (TM) yr(-1)). Such properties are typically seen in the low-z extreme blue compact dwarf galaxies. The kinematics of the gas is inconsistent with that of an extended disc and the gas is part of either a large scale wind or cold accretion. We detect Ly alpha emission from the z(abs) = 3.2477 DLA [having log N(H i) = 21.12 +/- 0.10 and [Zn/H] = -0.97 +/- 0.13]. The Ly alpha emission is redshifted with respect to the metal absorption lines by 320 km s(-1), consistent with the location of the red hump expected in radiative transport models. We derive SFR similar to 0.2-1.7 M-aS (TM) yr(-1) and Ly alpha escape fraction of a parts per thousand yen10 per cent. No other emission line is detected from this system. Because the DLA has a small velocity separation from the quasar (similar to 500 km s(-1)) and the DLA emission is located within a small projected distance (rho < 5 kpc), we also explore the possibility that the Ly alpha emission is being induced by the QSO itself. QSO-induced Ly alpha fluorescence is possible if the DLA is within a physical separation of 340 kpc to the QSO. Detection of stellar continuum light and/or the oxygen emission lines would disfavour this possibility. We do not detect any emission line from the remaining three systems.