The Euclid satellite has started the 6-year wide-field survey, and cosmology with weak gravitational lensing (WL) is one of the key science objectives. The deep multi-band data from ground-based telescopes is critical for photometric redshift estimation in Euclid’s WL analysis. To this end, the alliance of Hawaiian telescopes, UNIONS (Subaru g,z, CFHT u,r, and Pan-STARRS i), has been formed to provide multi-band optical data for the Euclid survey. Among UNIONS, WISHES has conducted the z-band imaging survey with Subaru HSC, covering 2,300 deg2 so far. However, the regions at lower latitudes (+15∘< Dec < +30∘) will not be observed by WISHES nor LSST. We propose an extension of such z-band survey, WISHES+, which observes 1,350 deg2 down to z≃ 23.4 mag (10σ within 2″ diameter) with 106 hours in HSC Queue mode. Combining WISHES/UNIONS data that are open to any Japanese researchers, the × 1.46 increase in the survey area strengthens the science objectives of WISHES/UNIONS, including accurate photometric redshift estimation and search for rare objects such as high-redshift quasars. The WISHES+ survey area at lower latitudes enables the Japanese community to perform multi-wavelength studies of interesting objects using Euclid, ALMA and future TMT.
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