Mapping the Morphology and Kinematics of a Lyα-selected Nebula at z = 3.15 with MUSE

Kelly N Sanderson,Johan Fynbo,Moire K M Prescott,Palle Møller,Lise Christensen

doi:10.3847/1538-4357/ac3077

Kelly N Sanderson, Johan Fynbo + Show 3 more

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https://doi.org/10.3847/1538-4357/ac3077

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Abstract

Abstract Recent wide-field integral-field spectroscopy has revealed the detailed properties of high-redshift Lyα nebulae, most often targeted due to the presence of an active galactic nucleus (AGN). Here, we use VLT/MUSE to resolve the morphology and kinematics of a nebula initially identified due to strong Lyα emission at z ∼ 3.2 (LABn06). Our observations reveal a two-lobed Lyα nebula, at least ∼173 pkpc in diameter, with a light-weighted centroid near a mid-infrared source (within ≈17.2 pkpc) that appears to host an obscured AGN. The Lyα emission near the AGN is also coincident in velocity with the kinematic center of the nebula, suggesting that the nebula is both morphologically and kinematically centered on the AGN. Compared to AGN-selected Lyα nebulae, the surface-brightness profile of this nebula follows a typical exponential profile at large radii (>25 pkpc), although at small radii, the profile shows an unusual dip at the location of the AGN. The kinematics and asymmetry are similar to, and the C iv and He ii upper limits are consistent with, other AGN-powered Lyα nebulae. Double-peaked and asymmetric line profiles suggest that Lyα resonant scattering may be important in this nebula. These results support the picture of the AGN being responsible for powering a Lyα nebula that is oriented roughly in the plane of the sky. Further observations will explore whether the central surface-brightness depression is indicative of either an unusual gas or dust distribution or variation in the ionizing output of the AGN over time.

Highlights

Recent studies have revealed extended diffuse Lyα emission that covers nearly 100% of the sky around high redshift galaxies (Wisotzki et al 2018; Leclercq et al 2020)
While many studies of diffuse Lyα emission have focused on Lyα-emitting galaxies (LAEs; Steidel et al 2000; Rauch et al 2008) or Lyα-emitting halos centered on active galactic nucleus (AGN) (e.g. Heckman et al 1991; Christensen et al 2006; Villar-Martın et al 2007; Cantalupo et al 2012, 2014; Borisova et al 2016), long-standing questions remain about the nature and powering mechanisms of the most dramatic Lyα-emitting regions in the Universe, i.e. giant Lyα nebulae;
The location of the obscured AGN lies within 17 pkpc of the light-weighted centroid of the Lyα emission, and the gas surrounding the AGN is at the kinematic center of the nebula

Summary

Introduction

Recent studies have revealed extended diffuse Lyα emission that covers nearly 100% of the sky around high redshift galaxies (Wisotzki et al 2018; Leclercq et al 2020). Heckman et al 1991; Christensen et al 2006; Villar-Martın et al 2007; Cantalupo et al 2012, 2014; Borisova et al 2016), long-standing questions remain about the nature and powering mechanisms of the most dramatic Lyα-emitting regions in the Universe, i.e. giant Lyα nebulae; (or Lyα “blobs,” LAB; e.g., Francis et al 1996; Steidel et al 2000; Matsuda et al 2004; Dey et al 2005; Prescott et al 2015a; Cai et al 2017; Cantalupo et al 2014) These nebulae show a range of unusual morphologies and in some cases trace out filaments connecting individual galaxies (Erb et al 2011; Arrigoni Battaia et al 2019). They do appear to reside preferentially in overdense regions (e.g., Steidel et al 2000; Prescott et al 2009; Yang et al 2009), but the frequent lack of obvious ionizing sources in or near many of these nebulae makes their energetics difficult to interpret (but see Overzier et al 2013)

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