(Proposal ID) S11A-016

(PI) Iwata, Ikuru

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

(Abstract)
Iwata et al. (2009) disclosed the existence of galaxies with strong Lyman 
continuum 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 are comparable to or 
exceed the highest possible values for standard stellar population models, and 
these may suggest the presence of extremely metal-poor or even metal-free 
stellar populatios. One caveat is that the extraordinary environment of the 
SSA22 may affect the LyC escape from galaxies; the effect is not 
straightforward - massive reservior of neutral Hi gas could reduce the 
probability of LyC photons reaching us, but on the other hand aggregation of 
massive star-forming galaxies may enhance ionized fraction of IGM around 
galaxies. In order to determine the average escape fraction of LyC at z~3, 
we require an observation in a general blank field. We propose a NB imaging 
search for LyC in the GOODS-N, where many z=3.1 Lyalpha emitters as well as 
Lyman break galaxies with spectroscopic redshifts are available. A wealth of 
multi-wavelength data in the GOODS-N should give us a clue to understand the 
property of strong LyC sources.