The WISSH quasars project. VIII. Outflows and metals in the circum-galactic medium around the hyper-luminous z ∼ 3.6 quasar J1538+08

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. <BR /> 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. <BR /> Methods: We analyse VLT/MUSE observations of the quasar J1538+08 (L<SUB>bol</SUB> = 6 × 10<SUP>47</SUP> erg s<SUP>-1</SUP>), and we performed a search for extended UV emission lines to characterise its morphology, emissivity, kinematics, and metal content. <BR /> Results: We report the discovery of a very luminous (∼2 × 10<SUP>44</SUP> erg s<SUP>-1</SUP>), giant Lyα nebula and a likely associated extended (75 kpc) CIV nebula. The Lyα nebula emission exhibits moderate blueshift (∼440 km s<SUP>-1</SUP>) compared to the quasar systemic redshift and a large average velocity dispersion (σ¯<SUB>v</SUB> ∼ 700 km s<SUP>-1</SUP>) across the nebula, while the CIV nebula shows average velocity dispersion of σ¯<SUB>v</SUB> ∼ 350 km s<SUP>-1</SUP>. 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<SUP>-1</SUP>) systemic one plus a broad (σ ∼ 1200 km s<SUP>-1</SUP>), blueshifted (∼1500 km s<SUP>-1</SUP>) one. <BR /> 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. <P />The reduced datacube is only available at the CDS via anonymous ftp to <A href="http://cdsarc.u-strasbg.fr/">http://cdsarc.u-strasbg.fr</A> (ftp://130.79.128.5) or via <A href="http://cdsarc.u-strasbg.fr/viz-bin/cat/J/A+A/635/A157">http://cdsarc.u-strasbg.fr/viz-bin/cat/J/A+A/635/A157</A> <P />Based on data obtained with the European Southern Observatory Very Large Telescope, Paranal, Chile, under Programme 099.A-0316(A).