SILVERRUSH. XII. Intensity Mapping for Lyα Emission Extending over 100–1000 Comoving Kpc around z ∼ 2−7 LAEs with Subaru HSC-SSP and CHORUS Data
Shotaro Kikuchihara, Yuichi Harikane, Masami Ouchi, Yoshiaki Ono, Takatoshi Shibuya, Ryohei Itoh, Ryota Kakuma, Akio Inoue, Haruka Kusakabe, Kazuhiro Shimasaku, Rieko Momose, Yuma Sugahara, Satoshi Kikuta, Shun Saito, Nobunari Kashikawa, Haibin Zhang, Chien‐Hsiu Lee
Abstract
Abstract We conduct intensity mapping to probe for extended diffuse Ly α emission around Ly α emitters (LAEs) at z ∼2−7, exploiting very deep (∼26 mag at 5 σ ) and large-area (∼4.5 deg 2 ) Subaru/Hyper Suprime-Cam narrowband (NB) images and large LAE catalogs consisting of a total of 1540 LAEs at z = 2.2, 3.3, 5.7, and 6.6 obtained by the HSC-SSP and CHORUS projects. We calculate the spatial correlations of these LAEs with ∼1–2 billion pixel flux values of the NB images, deriving the average Ly α surface brightness (SB Ly α ) radial profiles around the LAEs. By carefully estimating systematics such as fluctuations of sky background and point-spread functions, we detect Ly α emission at 100–1000 comoving kpc around z = 3.3 and 5.7 LAEs at the 3.2 σ and 3.7 σ levels, respectively, and tentatively (=2.0 σ ) at z = 6.6. The emission is as diffuse as ∼10 −20 –10 −19 erg s −1 cm −2 arcsec −2 and extended beyond the virial radius of a dark matter halo with a mass of 10 11 M ⊙ . While the observed SB Ly α profiles have similar amplitudes at z = 2.2–6.6 within the uncertainties, the intrinsic SB Ly α profiles (corrected for the cosmological dimming effect) increase toward high redshifts. This trend may be explained by increasing hydrogen gas density due to the evolution of the cosmic volume. Comparisons with theoretical models suggest that extended Ly α emission around an LAE is powered by resonantly scattered Ly α photons in the CGM and IGM that originate from the inner part of the LAE and/or neighboring galaxies around the LAE.