101. Imaging of diffuse HI absorption structure in the SSA22 protocluster region at z = 3.1
- Author
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Yuichi Matsuda, Akio K. Inoue, Masami Ouchi, Shiro Mukae, Takuya Otsuka, Hideki Umehata, Tomoki Hayashino, Toru Yamada, and Ken Mawatari
- Subjects
Physics ,COSMIC cancer database ,Field (physics) ,010308 nuclear & particles physics ,FOS: Physical sciences ,Astronomy and Astrophysics ,Astrophysics::Cosmology and Extragalactic Astrophysics ,Astrophysics ,Astrophysics - Astrophysics of Galaxies ,01 natural sciences ,Galaxy ,Space and Planetary Science ,galaxies: high-redshift ,Intergalactic medium ,Astrophysics of Galaxies (astro-ph.GA) ,0103 physical sciences ,intergalactic medium ,large-scale structure of Universe ,Background light ,Absorption (electromagnetic radiation) ,010303 astronomy & astrophysics ,Astrophysics::Galaxy Astrophysics - Abstract
Using galaxies as background light sources to map intervening Lya absorption is a novel approach to study the interplay among galaxies, the circum-galactic medium (CGM), and the intergalactic medium (IGM). Introducing a new measure of z = 3.1$ HI Lya absorption relative to the cosmic mean, Delta_NB497, estimated from photometric data of star-forming galaxies at 3.3 < z < 3.5, we have made two-dimensional Delta_NB497 maps in the z = 3.1 SSA22 proto-cluster region and two control fields (SXDS and GOODS-N fields) with a spatial resolution of ~ 5 comoving Mpc. The Delta_NB497 measurements in the SSA22 field are systematically larger than those in the control fields, and this HI absorption enhancement extends more than 50 comoving Mpc. The field-averaged (i.e., ~50 comoving Mpc scale) Delta_NB497 and the overdensity of Lya emitters (LAEs) seem to be correlated, while there is no clear dependency of the Delta_NB497 on the local LAE overdensity in a few comoving Mpc scale. These results suggest that diffuse HI gas spreads out in/around the SSA22 proto-cluster. We have also found an enhancement of Delta_NB497 at a projected distance < 100 physical kpc from the nearest z = 3.1 galaxies at least in the SSA22 field, which is probably due to HI gas associated with the CGM of individual galaxies. The HI absorption enhancement in the CGM-scale tends to be weaker around galaxies with stronger Lya emission, which suggests that the Lya escape fraction from galaxies depends on hydrogen neutrality in the CGM., 13 pages, 11 figures, 1 table, accepted to MNRAS
- Published
- 2017