# Ly$\alpha$ view around a z=2.84 hyperluminous QSO at a node of the cosmic web

## TL;DR

This study uses deep narrow-band imaging to map Ly$ ext{alpha}$ emitters around a hyperluminous QSO at z=2.84, revealing large-scale structures, LAB distributions, and a diffuse nebula likely illuminated by cold filaments.

## Contribution

First wide-field Ly$ ext{alpha}$ mapping around a hyperluminous QSO at high redshift, linking LABs and diffuse nebulae to large-scale cosmic web structures.

## Key findings

- LABs cluster around the QSO and align with large-scale structures.
- A diffuse Ly$ ext{alpha}$ nebula is detected along a filamentary structure.
- LABs are more prevalent in denser environments near the QSO.

## Abstract

We report on the results of deep and wide-field (1.1 deg$^2$) narrow-band observations with Subaru/Hyper Suprime-Cam (HSC) of a field around a hyperluminous QSO (HLQSO), HS1549+1919, residing in a protocluster at $z=2.84$, to map the large-scale structure of Ly$\alpha$ emitters (LAEs). One HSC pointing enables us to detect 3490 LAEs and 76 extended Ly$\alpha$ blobs (LABs), probing diverse environments from voids to protoclusters. The HLQSO is found to be near the center of the protocluster, which corresponds to the intersection of $\sim$100 cMpc-scale structures of LAEs. LABs are basically distributed along the large-scale structure, with larger ones particularly clustered around the HLQSO, confirming a previously noted tendency of LABs to prefer denser environments. Moreover, the shapes of LABs near the HLQSO appear to be aligned with the large-scale structure. Finally, a deep Ly$\alpha$ image reveals a diffuse Ly$\alpha$ nebula along a filamentary structure with no luminous UV/sub-mm counterpart. We suggest that the diffuse nebula is due to a cold filament with high clumping factor illuminated by the QSO, with a required high clumpiness provided by unresolved residing halos of mass $\leq 10^{9-10}M_\odot$.