(Proposal ID) S13A-033

(PI) Iwata, Ikuru

(Proposal Title)
Ionizing Radiation from High-z Galaxies in the GOODS-N

(Abstract)
This is a resubmission of the program approved in S11A which failed in data 
acquisition due to bad weather. Iwata et al.~(2009) disclosed the existence of 
galaxies with strong   Lyman continuum (LyC) emission in the SSA22 field, the 
proto-cluster region  at z~3.1, through the special narrow-band (NB) imaging 
with Suprime-Cam. Their LyC/UV flux ratios are unexpectedly high, and some of 
them exceed the highest possible values for standard stellar population models.
These may suggest the presence of extremely metal-poor or even metal-free 
stellar populations.  On the other hand, there is a report that fraction of 
strong LyC sources among star-forming galaxies at z~3 could be much smaller. 
This apparent conflict may indicate either (1) UV luminosity dependence of LyC 
escape fraction or (2) in the SSA22 massive concentration of star-forming 
galaxies enhance LyC escape. In order to disclose the nature of LyC escape at 
z~3, we propose sensitive LyC search with NB imaging in the GOODS-N. With 
large sample of LBGs and LAEs in wide UV luminosity range, we will examine the 
luminosity dependence of escape fraction and clarify whether the frequency of 
strong LyC sources is different in the general field and in the over-density 
region.