The MUSE view of Lyman-α nebulae in high redshift radio galaxies

¹ Dipartimento di Fisica, Università degli Studi di Torino, Via Pietro Giuria 1, 10125 (Torino), Italy
² INAF – Osservatorio Astrofisico di Torino, Via Osservatorio 20, I-10025 Pino Torinese, Italy
³ Osservatorio di Astrofisica e Scienza dello Spazio di Bologna Via Gobetti 93/3, I-40129 Bologna, Italy

^⋆ Corresponding author.

Received: 21 January 2025
Accepted: 5 May 2025

Abstract

We present the results from VLT/MUSE integral field spectroscopic observations of the Lyα emission nebulae associated with 11 high redshift (z≥2.9) radio galaxies (HzRGs) with Dec < 25°. When considering the additional nine sources with archival MUSE data available, these observations extend the coverage to half of the currently known HzRGs. We cannot confirm the original identification of two of the observed sources, as no Lyα emission was detected. We produced narrowband images centered on the Lyα line, extracted their nuclear spectra, mapped their ionized gas kinematics, and derived the Lyα surface-brightness profiles (SBPs). The SBPs are generally well reproduced by an exponential law with a typical scale length of ∼20−30 ckpc. We measured emission line ratios, finding most sources in agreement with an AGN origin for their gas ionization, with a single object hinting at strong star formation. Regarding the connection between the radio and ionized gas emission, we find that while the Lyα nebulae are preferentially aligned with the direction of the radio emission, there is no clear correlation in terms of size or gas kinematics, and only a weak trend connects their radio and Lyα luminosities. The alignment is most likely the result of anisotropic nuclear emission rather than a direct impact of the jets into the ionized gas.