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

We conduct intensity mapping to probe for extended diffuse Ly alpha emission around Ly alpha emitters (LAEs) at z similar to 2-7, exploiting very deep (similar to 26 mag at 5 sigma) and large-area (similar to 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 similar to 1-2 billion pixel flux values of the NB images, deriving the average Ly alpha surface brightness (SBLy alpha ) radial profiles around the LAEs. By carefully estimating systematics such as fluctuations of sky background and point-spread functions, we detect Ly alpha emission at 100-1000 comoving kpc around z = 3.3 and 5.7 LAEs at the 3.2 sigma and 3.7 sigma levels, respectively, and tentatively (=2.0 sigma) at z = 6.6. The emission is as diffuse as similar to 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 (circle dot). While the observed SBLy alpha profiles have similar amplitudes at z = 2.2-6.6 within the uncertainties, the intrinsic SBLy alpha 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 alpha emission around an LAE is powered by resonantly scattered Ly alpha photons in the CGM and IGM that originate from the inner part of the LAE and/or neighboring galaxies around the LAE.

Automated summary

Intensity mapping is used to study the extended diffuse Lyα emission around Lyα emitters (LAEs) at redshifts of approximately 2-7. The emission is detected at 100-1000 comoving kpc around z = 3.3 and 5.7 LAEs, and tentatively at z = 6.6. The emission is as diffuse as 10(-20)-10(-19) erg s(-1) cm(-2) arcsec(-2) and extends beyond the virial radius of a dark matter halo. The intrinsic Lyα surface brightness profiles increase with redshift, possibly due to increasing hydrogen gas density. The emission is likely powered by resonantly scattered Lyα photons.