(Proposal ID) S15B-050

(PI) Utsumi, Yosuke

(Proposal Title)
Custom-made narrow-band filter imaging around a QSO at z = 6.4

(Abstract)
QSOs have been thought to trace highly biased regions, where the present-day 
massive galaxy clusters will form. However galaxy clustering around QSOs at 
z > 6 had not been detected while strong overdensity of star-forming galaxies 
has been found around QSOs at 2 < z < 5. It implies that ionization photons 
from high redshift QSO would suppress galaxy formation significantly. 
Previously, we found an overdensity of Lyman break galaxies around a QSO at 
z=6.4 (Utsumi et al. 2010). This may be a discovery of the most distant 
proto-cluster around a QSO. However, a number of detected galaxies was only 
seven, resulting that it was hard to say anything conclusive. Here we propose 
an imaging observation with the newly developed custom-made narrow-band filter 
to capture Lyalpha emission from 50-100 young galaxies located at z=6.4. 
Much more sensitive narrow-band imaging can prove the existence of the proto-
cluster, and also will show the luminosity and morphology of the giant (22kpc)
 Lyalpha blob, which we also discovered previously (Goto et al. 2009). This 
will be a confirmation of the most distance galaxy clustering around QSO at 
z=6.4, and provides us with an important observational constraints on the UV 
radiation suppression of galaxy formation.