3D tomography of the giant Lyα nebulae of z ≈ 3–5 radio-loud AGN

¹ Astronomisches Rechen-Institut, Zentrum für Astronomie der Universität Heidelberg, Mönchhofstr. 12-14, 69120 Heidelberg, Germany
e-mail: wuji.wang@uni-heidelberg.de; wuji.wang_astro@outlook.com
² European Southern Observatory, Karl-Schwarzchild-Str. 2, 85748 Garching, Germany
³ Cosmic Dawn Center, Copenhagen, Denmark
⁴ DTU Space, Technical University of Denmark, Elektronvej 327, 2800 Lyngby, Denmark
⁵ Centre for Extragalactic Astronomy, Department of Physics, Durham University, South Road, Durham DH1 3LE, UK
⁶ Centro de Astrobiología, CSIC-INTA, Ctra. de Torrejón a Ajalvir, km 4, 28850 Torrejón de Ardoz, Madrid, Spain
⁷ Univ. Lyon, Univ. Lyon1, ENS de Lyon, CNRS, Centre de Recherche Astrophysique de Lyon UMR5574, 69230 Saint-Genis-Laval, France
⁸ International Centre for Radio Astronomy Research, Curtin University, 1 Turner Avenue, Bentley, WA 6102, Australia
⁹ Max-Planck-Institut fur Astrophysik, Karl-Schwarzschild-Str 1, 85748 Garching bei München, Germany
¹⁰ Instituto de Astrofísica e Ciências do Espaço, Universidade do Porto, CAUP, Rua das Estrelas, 4150-762 Porto, Portugal
¹¹ Institute for Computational Astrophysics and Department of Astronomy & Physics, Saint Mary’s University, 923 Robie Street, Halifax, NS B3H 3C3, Canada
¹² Physics Department, University of Johannesburg, 5 Kingsway Ave, Rossmore, Johannesburg 2092, South Africa

Received: 14 March 2023
Accepted: 26 September 2023

Abstract

Lyα emission nebulae are ubiquitous around high-redshift galaxies and are tracers of the gaseous environment on scales out to ≳100 pkpc (proper kiloparsec). High-redshift radio galaxies (HzRGs, type-2 radio-loud quasars) host large-scale nebulae observed in the ionised gas differ from those seen in other types of high-redshift quasars. In this work, we exploit MUSE observations of Lyα nebulae around eight HzRGs (2.92 < z < 4.51). All of the HzRGs have large-scale Lyα emission nebulae with seven of them extended over 100 pkpc at the observed surface brightness limit (∼2 − 20 × 10⁻¹⁹ erg s⁻¹ cm⁻² arcsec⁻²). Because the emission line profiles are significantly affected by neutral hydrogen absorbers across the entire nebulae extent, we performed an absorption correction to infer maps of the intrinsic Lyα surface brightness, central velocity, and velocity width, all at the last scattering surface of the observed Lyα photons. We find the following: (i) that the intrinsic surface brightness radial profiles of our sample can be described by an inner exponential profile and a power law in the low luminosity extended part; (ii) our HzRGs have a higher surface brightness and more asymmetric nebulae than both radio-loud and radio-quiet type-1 quasars; (iii) intrinsic nebula kinematics of four HzRGs show evidence of jet-driven outflows but we find no general trends for the whole sample; (iv) a relation between the maximum spatial extent of the Lyα nebula and the projected distance between the active galactic nuclei (AGN) and the centroids of the Lyα nebula; and (v) an alignment between radio jet position angles and the Lyα nebula morphology. All of these findings support a scenario in which the orientation of the AGN has an impact on the observed nebular morphologies and resonant scattering may affect the shape of the surface brightness profiles, nebular kinematics, and relations between the observed Lyα morphologies. Furthermore, we find evidence showing that the outskirts of the ionised gas nebulae may be ‘contaminated’ by Lyα photons from nearby emission halos and that the radio jet affects the morphology and kinematics of the nebulae. Overall, this work provides results that allow us to compare Lyα nebulae around various classes of quasars at and beyond cosmic noon (z ∼ 3).