GMOS SV program 67

The aim of this program is to obtain deep imaging to search for high-redshift galaxies, either associated with the z=4 QSO PMN2314+0201 or in the field. This quasar is radio-loud, which, based on evidence from lower redshifts, may indicate that it lies in a richer cluster environment than radio-quiet counterparts. Deep i and g band imaging has already been obtained during GMOS commissioning (10 sigma limits of about g=27.2, i=26.1 - fainter than L* at z=4) and several very red objects have been identified in the field - essentially g-band dropouts. The deep r band imaging proposed here will allow us to determine whether these objects are likely to be at z about 4 or lower redshift, red galaxies. Low redshift, red galaxies will be red in both g-r and r-i whereas young, high-redshift galaxies will be red in g-r (because of Ly-alpha and Lyman limit absorption) but relatively blue in r-i.