The WISSH quasars project

VIII. Outflows and metals in the circum-galactic medium around the hyper-luminous z  ∼  3.6 quasar J1538+08^⋆⋆⋆

¹ INAF-Osservatorio Astronomico di Roma, Via Frascati 33, 00078 Monteporzio Catone, Italy
e-mail: andrea.travascio@inaf.it
² Department of Physics, University of Rome “Tor Vergata”, Via della Ricerca Scientifica 1, 00133 Rome, Italy
³ Università degli Studi di Roma “Sapienza”, Piazzale Aldo Moro 5, 00185 Roma, Italy
⁴ Department of Physics, ETH Zurich, Wolfgang-Pauli-Strasse 27, 8093 Zurich, Switzerland
⁵ European Southern Observatory, Karl-Schwarzschild-Str. 2, 85748 Garching bei Munchen, Germany
⁶ Max-Planck-Institut fur Astrophysik, Karl-Schwarzschild-Str 1, 85748 Garching, Germany
⁷ Observatoire de Genève, Université de Genève, 51 Ch. des Maillettes, 1290 Versoix, Switzerland
⁸ INAF, Istituto di Astrofisica Spaziale e Fisica Cosmica – Milano, Via A. Corti 12, 20133 Milano, Italy
⁹ INAF Osservatorio Astronomico di Trieste, Via G.B. Tiepolo, 11, Trieste 34143, Italy
¹⁰ Scuola Normale Superiore, Piazza dei Cavalieri 7, 56126 Pisa, Italy
¹¹ Dipartimento di Matematica e Fisica, Università Roma Tre, Via della Vasca Navale 84, 00146 Roma, Italy
¹² Dipartimento di Fisica e Astronomia, Università di Bologna, Via Piero Gobetti 93/2, 40129 Bologna, Italy
¹³ INAF-Osservatorio di Astrofisica e Scienza dello Spazio di Bologna, Via Piero Gobetti 93/3, 40129 Bologna, Italy

Received: 27 June 2019
Accepted: 15 January 2020

Abstract

Context. In recent years, Lyα nebulae have been routinely detected around high redshift, radio-quiet quasars thanks to the advent of the highly sensitive integral field spectrographs. Constraining the physical properties of the Lyα nebulae is crucial for a full understanding of the circum-galactic medium (CGM). The CGM acts both as a repository for intergalactic and galactic baryons as well as a venue of feeding and feedback processes. The most luminous quasars are privileged test-beds to study these processes, given their large ionising fluxes and dense CGM environments in which they are expected to be embedded.

Aims. We aim to characterise the rest-frame ultraviolet (UV) emission lines in the CGM around a hyper-luminous, broad emission line, radio-quiet quasar at z ∼ 3.6, which exhibits powerful outflows at both nuclear and host galaxy scales.

Methods. We analyse VLT/MUSE observations of the quasar J1538+08 (L_bol = 6 × 10⁴⁷ erg s⁻¹), and we performed a search for extended UV emission lines to characterise its morphology, emissivity, kinematics, and metal content.

Results. We report the discovery of a very luminous (∼2 × 10⁴⁴ erg s⁻¹), giant Lyα nebula and a likely associated extended (75 kpc) CIV nebula. The Lyα nebula emission exhibits moderate blueshift (∼440 km s⁻¹) compared to the quasar systemic redshift and a large average velocity dispersion (σ¯_v ∼ 700 km s⁻¹) across the nebula, while the CIV nebula shows average velocity dispersion of σ¯_v ∼ 350 km s⁻¹. The Lyα line profile exhibits a significant asymmetry towards negative velocity values at 20−30 kpc south of the quasar and is well parametrised by the following two Gaussian components: a narrow (σ ∼ 470 km s⁻¹) systemic one plus a broad (σ ∼ 1200 km s⁻¹), blueshifted (∼1500 km s⁻¹) one.

Conclusions. Our analysis of the MUSE observation of J1538+08 reveals metal-enriched CGM around this hyper-luminous quasar. Furthermore, our detection of blueshifted emission in the emission profile of the Lyα nebula suggests that powerful nuclear outflows can propagate through the CGM over tens of kiloparsecs.