The origin of LyA emitter with large Equivalent width in SSA22 protocluster

Kohei Shinoka

The equivalent width (EW) of LyA emission represents the strength of ionization, if the LyA is originated by photoionization by young stars.As it represents the relative strength of ionization continuum to the UV continuum at the LyA wavelength, it constrains the hardness ofthe spectra, or the population of young stars.We are conducting the wide-field survey for LyA emitters at the SSA22 protocluster field, in which the large density excess of Lyman Break Galaxies was first discovered (Yamada et al. 2012).In our previous study, we found that there are a large fraction of LyA emitters whose EW is larger than 200A, which needs the presence ofextremely hot stars in case of photoionization, but the continuumimages obtained so far was not deep enough to measure the true EW values for those objects with EW larger than 300A.To overcome the situation, we newly obtained deeper continuum imageswith Subaru Suprime-Cam (B,V, for SSA22-Sb1 'protocluster' area) and Hyper Suprime-Cam (g, for the large-scale 'superstructure' area). We combined these broad-band images to make the continuum images significantly deeper than the previous ones. We investigated the distribution of EW of LyA emitters and found that the cumulative distributions of EW in this field clearly differ from those of general fields, SXDS, SDF, and GOODS-North. This indicates that the star formation in the large-scale high-density field, such as SSA22,could be regulated by the mechanism which is different from that ofgeneral fields at z~3.In my presentation , I will show the results of statistical analysis including Kolmogorov-Smirnov test as well as the observedproperties of the objects with extreme LyA EW.