SILVERRUSH. IX. Lya Intensity Mapping with Star-Forming Galaxies at z=5.7 and 6.6: A Possible Detection of Extended Lya Emission at $\gtrsim$100 comoving kpc around and beyond the Virial-Radius Scale of Galaxy Dark Matter Halos

Abstract

We present results of the cross-correlation Ly$\alpha$ intensity mapping with Subaru/Hyper Suprime-Cam (HSC) ultra-deep narrowband images and Ly$\alpha$ emitters (LAEs) at $z=5.7$ and $6.6$ in a total area of $4$ deg${}^2$. Although overwhelming amount of data quality controls have been performed for the narrowband images, we further conduct extensive analysis evaluating systematics of large-scale point-spread-function wings, sky subtractions, and unknown errors based on physically uncorrelated signals and sources found in real HSC images and object catalogs, respectively. Removing the systematics, we carefully calculate cross-correlations between Ly$\alpha$ intensity of the narrowband images and the LAEs. We tentatively identify very diffuse Ly$\alpha$ emission with the $\simeq 3\sigma$ ($\simeq 2\sigma$) significance at $\gtrsim$ 100 comoving kpc (ckpc) far from the LAEs at $z=5.7$ ($6.6$), around and probably even beyond a virial radius of star-forming galaxies with $M_{\mathrm{h}}\sim 10^{11}{M}_{\odot }$. The diffuse Ly$\alpha$ emission possibly extends up to $1$,$000$ ckpc with the surface brightness of $10^{-20}$-$10^{-19}$ erg s${}^{-1}$ cm${}^{-2}$ arcsec${}^{-2}$. We confirm that the small-scale ($<150$ ckpc) Ly$\alpha$ radial profiles of LAEs are consistent with those obtained by recent MUSE observations. Comparisons with numerical simulations suggest that the large-scale ($\sim 150$-$1$,$000$ ckpc) Ly$\alpha$ emission are not explained by unresolved faint neighboring galaxies including satellites, but by a combination of Ly$\alpha$ photons emitted from the central LAE and other unknown sources, such as cold-gas streams and galactic outflow. We find no evolution in the Ly$\alpha$ radial profiles of our LAEs from $z=5.7$ to $6.6$, where theoretical models predict a flattening of the profile slope made by cosmic reionization, albeit with our moderately large observational errors.

11 pages, 6 figures, accepted for publication in ApJ

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• Line-Intensity Mapping: Theory Review
• SILVERRUSH XI: Constraints on the Ly$\alpha$ luminosity function and cosmic reionization at $z=7.3$ with Subaru/Hyper Suprime-Cam
• The MUSE eXtremely Deep Field: Individual detections of Lyα haloes around rest-frame UV-selected galaxies at z~2.9-4.4
• Surface Brightness Profile of Lyman-$\alpha$ Halos out to 320 kpc in HETDEX
• ZELDA: fitting Lyman-alpha line profiles using deep learning
• The cosmic web in Lyman-alpha emission
• Median Surface Brightness Profiles of Lyman-$\alpha$ Haloes in the MUSE Extremely Deep Field
• Forecasts and Statistical Insights for Line Intensity Mapping Cross-Correlations: A Case Study with 21cm x [CII]
• SILVERRUSH. XI. Intensity Mapping for Lya Emission Extending over $100-1000$ comoving kpc around $z\sim 2-7$ LAEs with Subaru HSC-SSP and CHORUS Data
• A multi-tracer empirically-driven approach to line-intensity mapping lightcones
• The Lyman-alpha and Continuum Origins Survey II: the connection between the escape of ionizing radiation and Lyman-alpha halos in star-forming galaxies
• Scattering of Lyα Photons through the Reionizing Intergalactic Medium: I. Spectral Energy Distribution
• zELDA II: reconstruction of galactic Lyman-alpha spectra attenuated by the intergalactic medium using neural networks
• Lyα Intensity Mapping in HETDEX: Galaxy-Lyα Intensity Cross-Power Spectrum
• Can luminous Lyman alpha emitters at $z$ $\simeq$ 5.7 and $z$ $\simeq$ 6.6 suppress star formation?