Revealed by the H i Tomographic Mapping Technique

We present an IGM Hi tomography map in a survey volume of 16 × 19 × 131 h−3comoving Mpc (cMpc) centered at MAMMOTH-1 nebula and three neighbouring quasars at z = 2.3. MAMMOTH-1 nebula is an enormous Lyα nebula (ELAN), hosted by a type-II quasar dubbed MAMMOTH1-QSO, that extends over 1 h−1 cMpc with not fully clear physical origin. Here we investigate the Hi-gas distribution around MAMMOTH1-QSO with the ELAN and three neighbouring type-I quasars, making the IGM Hi tomography map with a spatial resolution of 2.6 h−1 cMpc. Our Hi tomography map is reconstructed with Hi Lyα forest absorption of bright background objects at z = 2.4−2.9: one eBOSS quasar and 16 Keck/LRIS galaxy spectra. We estimate the radial profile of Hi flux overdensity for MAMMOTH1-QSO, and find that MAMMOTH1-QSO resides in a volume with significantly weak Hi absorption. This suggests that MAMMOTH1-QSO has a proximity zone where quasar illuminates and photo-ionizes the surrounding Hi gas and suppresses Hi absorption, and that the ELAN is probably a photo-ionized cloud embedded in the cosmic web. The Hi radial profile of MAMMOTH1-QSO is very similar to those of three neighbouring type-I quasars at z = 2.3, which is compatible with the AGN unification model. We compare the distributions of the Hi absorption and star-forming galaxies in our survey volume, and identify a spatial offset between density peaks of star-forming galaxies and Hi gas. This segregation may suggest anisotropic UV background radiation created by star-forming galaxy density fluctuations. mukae@icrr.u-tokyo.ac.jp ar X iv :1 91 0. 02 96 2v 1 [ as tr oph .G A ] 7 O ct 2 01 9