Abstract:
We report the Subaru Hyper Suprime-Cam (HSC) discovery of two Lya blobs (LABs), dubbed z70-1 and z49-1 at z=6.965 and z=4.888 respectively, that are Lya emitters with a bright and spatially-extended Lya emission, and present the photometric and spectroscopic properties of a total of seven LABs; the two new LABs and five previously-known LABs at z=5.7-6.6. The z70-1 LAB shows the extended Lya emission with a scale length of 1.4$\pm$0.2 kpc about three times larger than the UV continuum emission, making z70-1 the most distant LAB identified to date. All of the 7 LABs, except z49-1, exhibit no AGN signatures such as X-ray emission, NV1240 emission, or Lya line broadening, while z49-1 has a strong CIV1548 emission line indicating an AGN on the basis of the UV-line ratio diagnostics. We carefully model the point-spread functions of the HSC images, and conduct two-component exponential profile fitting to the extended Lya emission of the LABs. The Lya scale lengths of the core (star-forming region) and the halo components are $r_c$=0.6-1.2 kpc and $r_h$=2.0-13.8 kpc, respectively. The average $r_h$ of the LABs falls on the extrapolation of the $r_h$-Lya luminosity relation of the Lya halos around VLT/MUSE star-forming galaxies at the similar redshifts, suggesting that typical LABs are not special objects, but star-forming galaxies at the bright end.