S22B0083
S22B0083
The HSC-SSP has uniquely enabled blind searches of high-z protoclusters. Based on its S21A data release, we constructed a large sample of protocluster candidates at z∼3−5 over the 25 deg2 DUD layer. Here, we propose optical spectroscopy of g-dropout galaxies in the only >4σ overdensity that will be fully covered by allocated JWST observations. Rest-optical high-resolution imaging by JWST/NIRCam will open a window on the stellar population and structural properties of z∼4 galaxies in and around the overdensity. Exploiting the wide FoV of DEIMOS, we will identify which dropout galaxies feature Lyα emission, and at what strength. Direct probes of escaping Lyα emission will for the first time be contrasted to rest-optical sizes, axial ratios and morphologies, tracing the stellar distribution. The spectroscopic redshifts will securely separate foreground/background interlopers at the same general epoch within the first 1-2 billion years of cosmic history from genuine members of the overdense structure in 3D. The spec-z’s will sensitively improve constraints on stellar mass, age and dust content, which will be compared between field and overdense environments, as a function of 3D location within the protocluster, and between dropout galaxies with and without Lyα emission.
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