We present Keck/KCWI integral field spectrograph observations of the complex system surrounding SMM J02399−0136 (a lensed z=2.8 sub-mm galaxy), including an associated Lyα nebula, a dust-obscured, broad-absorption-line quasar, and neighboring galaxies. At a 3σ surface brightness contour of 1.6× 10−17 erg s−1 cm−2 arcsec−2, the Lyα nebula extends over 17 arcsec (≳140 physical kpc) and has a total Lyα luminosity of 2.5×1044ergs−1 (uncorrected for lensing). The nebula exhibits a kinematic shear of ∼ 1000 km s−1 over 100 pkpc with lowest velocities east of SMM J02399−0136 and increasing to the southwest. We also discover a bright, Lyα emitter, separated spatially and kinematically from the nebula, at a projected separation of ≈60 kpc from the quasar. This source has no clear central counterpart in deep HubbleSpaceTelescope imaging, giving an intrinsic Lyα rest-frame equivalent width greater than 312 A˚ (5-σ). We argue that this 'dark cloud' is illuminated by the quasar with a UV flux that is orders of magnitude brighter than the emission along our sightline. This result confirms statistical inferences that luminous quasars at z>2 emit UV radiation anisotropically. Future KCWI observations of other lines, e.g. Lyβ, HeII, CIV, etc, and with polarimetry will further reveal the origin of the Lyα nebula and nature of the dark cloud.
@article{arxiv.1903.03131,
title = {Discovery of a Lya emitting dark-cloud within z ~ 2.8 SMMJ02399-0136 system},
author = {Qiong Li and Zheng Cai and J. Xavier Prochaska and Fabrizio Arrigoni Battaia and Rob J. Ivison and Edith Falgarone and Sebastiano Cantalupo and Matt Matuszewski and James Don Neill and Ran Wang and Chris Martin and Anna Moore},
journal= {arXiv preprint arXiv:1903.03131},
year = {2019}
}