(Proposal ID) S11B-023

(PI) Kashikawa, Nobunari

(Proposal Title)
The first QSOs at z~6 and 7: Spectroscopy

(Abstract)
We propose to take follow-up spectroscopy for our primising QSO candidates 
at z ~7. We have obtained wide and deep zB/zR images with Subaru/Suprime-Cam 
for 7 deg^2 in total for three UKIDSS-DXS fields in order to select QSO 
candidates at z ~7. Using z_B - z_R and z_R - J color selection, we carefully 
selected 12 promising QSO candidates at z ~ 7. for z ~ 7 QSOs. This project is 
a new search for QSOs at z ~ 7 utilizing unique capabilities of wide-field 
imaging of Suprime-Cam, its high-sensitivity CCDs at ~ 1mum, and z_B/z_R 
filters to effectively isolate high-z QSOs from L/T dwarfs. By using Subaru 
deep i-band data, we also selected 90 faint QSO candidates at z ~ 6 down to 
z_R < 23.5. Our primary objective of this project is to determine the census 
of QSOs at z = 6 - 7. The constraint of QSO number density at the highest 
redshift is very important to revise formation and evolution models of early 
QSO/SMBH in a time scale as short as <1Gyr. The census of faint QSOs is also 
quite interesting in estimating the QSO contribution to the photon budget of 
cosmic reionization. The obtained high-z QSO sample will give precious 
opportunities for the current and future observational facilities to 
follow-up astronomy.