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

We report the results of a survey for fluorescent Lyα 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 Lyα emitters, compared with those of other nonfluorescent Lyα emitters. Our observational search detected 13 Lyα sources sparsely sampling a volume of ∼ 14,000 comoving Mpc3 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) ∼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. © 2007, The American Astronomical Society. All rights reserved.