Damped Lyman alpha absorber, QSO APM 08279+5255

Our best tracer of cold gas at high redshift is damped Lyman alpha absorbers (DLAs). The KPNO Mayall 4-meter telescope has been used to study DLA fields, and this picture shows the eight-by-eight arc minute central region of one such field, towards the quasar (QSO) known picturesquely as APM 08279+5255. The QSO appears red in this BVI image due to its redshift (z=3.91). There are about seven Lyman break galaxies (LBGs) with redshifts similar to that of the DLA in the portion of the field shown. The full MOSAIC camera data covers more than thirty arc minutes square, corresponding to forty-by-forty megaparsecs, enabling the science team to probe the clustering of LBGs around DLAs on scales of five to ten megaparsecs. See the March 2004 NOAO Newsletter (currently only available in PDF format).