Ionization and feedback in Ly$\alpha$ halos around two radio galaxies at z$\sim$2.5

TL;DR

This study investigates ionization and feedback processes in Lyα halos around two high-redshift radio galaxies, revealing outflows, absorption effects, and diverse spatial gas distributions through spectroscopic observations.

Contribution

It provides new spectroscopic data comparing gas properties along and perpendicular to radio axes, highlighting feedback-driven outflows and complex gas structures at z~2.5.

Findings

Detection of extended Lyα emission perpendicular to radio axes.

Evidence of outflowing gas along radio axes and in spherical shells.

Identification of giant UV-emitting structures possibly caused by feedback.

Abstract

We present new spectroscopic observations of two high redshift radio galaxies, TXS 0211-122 (z=2.34) and TXS 0828+193 (z=2.57), known to be associated with large Ly$\alpha$ halos. The observations were taken with the slits placed perpendicularly to the radio axis. With access to pre-existing Keck II observations taken with the slit placed along the radio axis we are able to compare the properties of the gas in different regions of the galaxies. In both objects we detect spatially extended Ly$\alpha$ emission perpendicularly to the radio axis. In TXS 0211-122, the flux and velocity profiles of Ly$\alpha$ are strongly affected by HI absorption/scattering. In line with previous studies, we find evidence for outflowing gas along the radio axis which may be the result of jet-gas interactions. In the slit oriented perpendicularly to the radio axis we find less perturbed gas kinematics, suggesting outflows of ionized gas in this object are focused along the radio jet axis. Additionally, we find evidence for a giant, UV-emitting arc or shell-like structure surrounding the radio galaxy Ly$\alpha$ halo, possibly resulting from feedback activity. In TXS 0828+193 a large Ly$\alpha$ halo ($\sim$56 kpc) is detected perpendicularly to the radio axis. Along both slit position angles we find evidence for outflowing gas, which we argue is part of an approximately spherical, expanding shell or bubble of gas powered by feedback activity in the central regions of the galaxy. Our results suggest a diversity in the spatial distribution of ionized outflows in powerful radio galaxies at z$\sim$2.5.