Plausible fluorescent Lyα emitters around the z=3.1 QSO 0420-388

We report the results of a survey for fluorescent Ly alpha emission carried out in the field surrounding the z = 3.1 quasar QSO 0420-388 using the Focal Reducer/Low Dispersion Spectrograph 2 (FORS2) instrument on the Very Large Telescope (VLT). We first review the properties expected for fluorescent Ly alpha emitters, compared with those of other nonfluorescent Ly alpha emitters. Our observational search detected 13 Ly alpha sources sparsely sampling a volume of similar to 14,000 comoving Mpc(3) around the quasar. The properties of these in terms of (1) the line equivalent width, (2) the line profile, and ( 3) the value of the surface brightness related to the distance from the quasar all suggest that several of these may be plausibly fluorescent. Moreover, their number is in good agreement with the expectation from theoretical models. One of the best candidates for fluorescence is sufficiently far behind QSO 0420-388 that it would imply that the quasar has been active for (at least) similar to 60 Myr. Further studies on such objects will give information about protogalactic clouds and on the radiative history (and beaming) of the high-redshift quasars.