1998A&A...332..814L

We present further observational results on our Lyα-only absorber identification project at low and intermediate redshifts. We combine CFHT/MOS imaging and spectroscopic observations of 25 galaxies in the field of the quasar 3C 286 (ze=0.849) with HST/FOS spectrum of the quasar between 1600 and 3000Å and HST/WFPC2 high spatial resolution imaging of some galaxies. Our results confirm our first conclusions on the nature of the intermediate redshift Lyα forest absorbers. A small fraction of them is tightly linked to galaxies, and most probably arise in the external parts of giant halos (R≃200h₅₀^–1kpc) around fairly luminous galaxies (M_AB(B)←19) of various spectral and morphological types, as shown by HST imaging of these objects. Most of the absorbing clouds appear to be only ``associated'' with galaxies, in the sense that they could trace the gaseous filaments or sheets of large-scale structures. Thus, as expected from a sample tracing large scale structures, these galaxies have various spectral types. We also find that groups of galaxies have always at least one associated Lyα absorption line.