(Proposal ID) S17B-129

(PI) Mukae, Shiro

(Proposal Title)
IGM Tomography of the Extremely Extended and Luminous Ly\alpha Nebulae

(Abstract)
We propose deep LRIS spectroscopy for background galaxies in remarkable giant 
Ly alpha nebulae of MAMMOTH-1 and Slug Nebula at z ~ 2.3, whose Ly alpha 
emission extends over 400 pkpc beyond the virial diameter. We will take 
spectra of the bright background galaxies at z_{photo} ~ 2.3-2.7 with MOS 
masks. The background galaxy spectra will provide IGM HI Ly alpha absorptions 
in the giant Ly alpha nebulae, and a tomographic reconstruction map of the IGM 
HI gas beyond the size of the giant Ly alpha nebulae. We combine the study of 
giant Ly alpha nebulae with IGM tomography, for the first time. Our goals are 
to test whether the Ly alpha emission mechanism scenarios of giant Ly alpha 
nebulae is i) the recombination radiation from HI gas that has been 
photoionized by the quasar or ii) the resonant scattering of Ly alpha produced 
in the quasar broad line region, and to investigate the HI extension of giant 
Ly alpha Nebula in the cosmic web, for understanding connection between giant 
Ly alpha nebulae and galaxy formation in large-scale structure. This is a 
pathfinder study for the planned Subaru/PFS survey being discussed by the PFS 
group, and an early completion of our spectroscopy is important for the PFS 
survey planning that is finished in about one year.