First investigation of the clustering environment of damped Lyα absorbers at z ∼

We report the first observations of the clustering environment of damped Lyman a absorption systems at z ≃ 4. Color selection and photometric redshifts were used to select 44 candidate Lyman-break galaxies brighter than I_AB = 25.5 from deep BRI images of the 35 arcmin² field containing the quasar BR 0951-04. Multislit spectroscopy of 35 candidate galaxies was performed and eight of these candidates have been confirmed as z > 3.5 Lyman-break galaxies. With only BRI photometry, the photometric redshifts are quite accurate for the spectroscopically confirmed galaxies but have a high rate of misclassification due to color degeneracies between Lyman-break galaxies and low-redshift ellipticals. Both of the z > 3.5 galaxies found within 15″ of the quasar line-of-sight appear to be causing absorption systems in the quasar spectrum. We use a battery of statistical tests to look for clustering in the redshift histogram of the z > 3.5 galaxies but do not find measurable clustering of these Lyman-break galaxies with the damped Lyα absorbers. With a larger sample of galaxies, our method should determine the cross-correlation between these objects, which probes the bias and hence the mass of the damped Lyα absorbers.