A radio galaxy at z=3.6 in a giant rotating Lyman $\alpha$ halo

TL;DR

This paper reports the discovery of a high-redshift radio galaxy with a giant, rotating Lyα halo exhibiting complex kinematics, providing insights into galaxy formation and gas dynamics at early cosmic times.

Contribution

It presents detailed observations of a z=3.57 radio galaxy with a large, rotating Lyα halo, revealing complex gas components and kinematics not previously documented at such redshifts.

Findings

Lyα halo extends over 135 kpc with high luminosity.

The gas shows three distinct kinematic components.

Evidence of large-scale rotation in the halo gas.

Abstract

We present the discovery and detailed observations of the radio galaxy 1243+036 (=4C 03.24) at a redshift of $z=3.57$. The most spectacular feature of 1243+036 is the presence of a Ly$\alpha$ halo of luminosity $\sim10^{44.5}$ ergs s$^{-1}$ which extends over$\sim20''$ (135 kpc). The narrow band imaging and the high resolution spectroscopy show that the Ly$\alpha$ gas has three distinct components: (i) gas with a high velocity dispersion (1550 km s$^{-1}$ FWHM) located inside the radio structure, (ii) enhanced Ly$\alpha$ emission blue shifted by 1100 km s$^{-1}$ at the location of the strong bend in the radio jet and (iii) Ly$\alpha$ emission extending out well beyond the radio lobes. This emission has a low velocity dispersion (250 km s$^{-1}$ FWHM) and a velocity gradient of 450 km s$^{-1}$ over the extent of the emission, indicative of large scale rotation. On the basis of these obserserations various mechanisms for the origin and kinematics of the Ly$\alpha$ halo are discussed.