(Proposal ID) S16A-006 (PI) Tadaki, Kenichi (Proposal Title) An ultra-deep Lyalpha+[OIII] dual narrow-band survey with HSC (Abstract) We propose ultra-deep Lyalpha imaging with the NB515 filter of Hyper Suprime- Cam. The primary goal is to detect filamentary Lyalpha structures beyond the virial radius, which can be a direct evidence for cold gas streams. The advantages of our approach are 1. ultra-deep (1sigma=3x10^{-19} erg s^{-1}cm^{-2}arcsec^{-2} in Lyalpha), 2. very wide area (1.8 deg^2), and 3. Lyalpha+[OIII] dual NB imaging at the same redshift range (z=3.23). In the COSMOS field, the HiZELS [OIII] NB survey has provided a clean sample of 152 Lyman break galaxies (LBGs) with [OIII] emission likely residing in halos with M_{halo}~10^{12}M_sun. Furthermore, the ultra-deep and wide-field imaging will, for the first time, unveil the halo mass of Lyalpha blobs (LABs) by the clustering analysis, as well as that of Lyalpha emitters (LAEs). The Lyalpha+ [OIII] matched survey is ideal for the study of cold gas streams or Lyalpha halos because we can investigate how the Lyalpha structures are affected by ionizing sources such AGN/starburst ([OIII] strength and [OIII]/UV), the halo mass (LAEs, LBGs, and LABs), and the environments.