DISCOVERY OF A LY-ALPHA GALAXY NEAR A DAMPED LY-ALPHA ABSORBER AT Z = 2.3

We report the detection of a galaxy associated with the damped Ly-alpha absorbing cloud seen at z = 2.309 toward the QSO PHL 957 (z(em) = 2.681). The galaxy was discovered in deep Fabry-Perot narrow-band CCD frames and was subsequently imaged spectroscopically. In addition to a strong but narrow Ly-alpha emission line (F(Ly-alpha) = 5.6 x 10(-16) ergs s-1 cm-2, FWHM approximately 700 km s-1) and weaker C IV and He II lines, the object shows continuum at V approximately 24, with a slope (in F-nu) rising slightly toward the red, similar to what is seen in high-redshift radio galaxies; however, the galaxy does not correspond to any known radio source in the literature. The detected emission lines and continuum are most easily interpreted as light from hot, recently formed stars, implying not only a sizable star formation rate (SFR greater-than-or-equal-to 5 M . yr-1) but also a scarcity of dust, which readily quenches Ly-alpha photons. The emission region appears to be marginally resolved spatially and is located 48" to the NW of the QSO, corresponding to a projected distance of 270h-1 kpc (for q0 = 0.1); the velocity difference with respect to the damped Ly-alpha cloud is approximately 350 km s-1. The spatial correlation of the absorbing cloud and the companion galaxy supports the interpretation of damped Ly-alpha clouds as objects fundamentally different from the lower column density Ly-alpha forest clouds, which show weak or no clustering. The absorption trough itself shows no Ly-alpha emission, extended or unresolved, in either the Fabry-Perot frames or in deep, moderate resolution (approximately 3 angstrom FWHM), two-dimensional spectra, down to a limiting flux (3-sigma) for an unresolved line of 2 x 10(-17) ergs s-1 cm-2, approximately 30 times fainter than the Ly-alpha flux detected from the companion galaxy. The lack of strong Ly-alpha emission from the absorbing cloud can be interpreted as evidence either for a low SFR or for heavy dust obscuration.