Ionization and feedback in Lyα haloes around two radio galaxies at z ~ 2.5

S. G. Morais, A. Humphrey, M. Villar-Martín, P. Lagos, M. M. Moyano, R. Overzier, S. Di Serego Alighieri, J. Vernet, C. A. C Fernandes

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 Lyα haloes. 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 Lyα emission perpendicularly to the radio axis. In TXS 0211−122, the flux
and velocity profiles of Lyα are strongly affected by H I 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 Lyα halo, possibly resulting from feedback activity.
In TXS 0828+193, a large Lyα halo (∼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 ∼ 2.5.

Keywords
galaxies: active – galaxies: high-redshift – galaxies: individual: TXS 0211-122 – galaxies: individual: TXS 0828+193.

Monthly Notices of the Royal Astronomical Society
Volume 465, Page 2698
November 2016

DOI: 10.1093/mnras/stw2926
ADS Bibliographic code: 2017MNRAS.465.2698M