IMAGING AND SPECTROSCOPY OF DAMPED LY-ALPHA QUASI-STELLAR OBJECT ABSORPTION-LINE CLOUDS

We present the results of a multifaceted search for line emission from the vicinities of high-redshift quasistellar object (QSO) absorption-line clouds, most of them damped Ly alpha systems at z greater than or similar to 2. Seven fields containing QSOs with known intervening damped Ly alpha absorbers were imaged with the GSFC Fabry-Perot Imager to search for diffuse redshifted Ly alpha. Apart from the one Ly alpha companion galaxy reported previously, no confirmed extended Ly alpha emission was detected down to 3 sigma flux levels of around 3 x 10(-17) ergs s(-1) cm(-2), corresponding to star formation rates less than or similar to 1 M. yr(-1), assuming case B recombination, a reasonable initial mass function, and negligible extinction by dust. One of the damped Ly alpha systems studied here, toward Q0836+113, has been reported to show faint, extended Ly alpha emission. While our Ly alpha images of that held are not sensitive enough to confirm the reported flux levels, we did detect and spectroscopically confirm redshifted [O II] lambda 3727 and continuum emission from a closer intervening system, a Mg II system at z = 0.788, at the same spatial position as the reported Ly alpha emission from the more distant object, and we suggest the possibility that all the observations of this field can be explained by the closer system alone. Six damped Ly alpha systems, including two that were imaged with the Fabry-Perot, were also imaged with two-dimensional long-slit CCD spectroscopy at similar to 2 Angstrom resolution in the core of the Ly alpha absorption line. No convincing Ly alpha emission was found from any of the systems, including Q0836+113, for which our sensitivity was again insufficient to confirm the previously reported extended Ly alpha emission. However, there is yet another independent claim of Ly alpha emission from that cloud, but spatially unresolved, in conflict with the report of extended emission; our observations do not reproduce the report of compact Ly alpha emission, which should have appeared at about the 7 sigma level. Although observationally allowable quantities of dust in the damped Ly alpha clouds can in some cases quench Ly alpha flux by up to several orders of magnitude, several of the damped clouds studied here are arguably metal and dust poor, leading us to believe that our limits on Ly alpha emission generally constrain the star formation rates to be less than or similar to 10 M. yr(-1), comparable to normal Sc galaxies today. Whatever their exact nature, the damped Ly alpha clouds therefore appear not to be spectacular primeval galaxies seen in the act of forming a galaxy's worth of stars.