  We carried out a target survey for Lyman break galaxies (LBGs) and Lyman
alpha emitters (LAEs) around QSO SDSS J0211-0009 at z=4.87. The deep and wide
broadband and narrowband imaging simultaneously revealed the perspective
structure of these two high-z populations. The LBGs without Ly-alpha emission
form a filamentary structure including the QSO, while the LAEs are distributed
around the QSO but avoid it within a distance of ~4.5Mpc. On the other hand, we
serendipitously discovered a protocluster with a significant concentration of
LBGs and LAEs where no strongly UV ionizing source such as a QSO or radio
galaxy is known to exist. In this cluster field, two populations are spatially
cross-correlated with each other. The relative spatial distribution of LAEs to
LBGs is in stark contrast between the QSO and the cluster fields. We also found
a weak trend showing that the number counts based on Ly-alpha and UV continuum
fluxes of LAEs in the QSO field are slightly lower than in the cluster field,
whereas the number counts of LBGs are almost consistent with each other. The
LAEs avoid the nearby region around the QSO where the local UV background
radiation could be ~100 times stronger than the average for the epoch. The
clustering segregation between LBGs and LAEs seen in the QSO field could be due
to either enhanced early galaxy formation in an overdense environment having
caused all the LAEs to evolve into LBGs, or local photoionization due to the
strong UV radiation from the QSO effectively causing a deficit in low-mass
galaxies like LAEs.
