Kavli Affiliate: Roberto Maiolino
| First 5 Authors: Francesco D’Eugenio, Francesco D’Eugenio, , ,
| Summary:
We report the discovery of a remarkably large and luminous line-emitting
nebula extending on either side of the Balmer-break galaxy JADES-GS-518794 at
z=5.89, detected with JADES JWST/NIRCam imaging in [O
III]$lambdalambda$4959,5007 and H$alpha$ and spectroscopically confirmed
with NIRCam/WFSS thanks to the pure-parallel SAPPHIRES programme. The
end-to-end velocity offset is $Delta v=830pm130$ km s$^-1$. Nebulae with
such large size and high luminosity (25-pkpc diameter, L[O III] = $1.2times
10^10$ L$_odot$) are routinely observed around bright quasars, unlike
JADES-GS-518794. With a stellar mass of $10^10.1$ M$_odot$, this galaxy is
at the knee of the mass function at z=6. Its star-formation rate declined for
some time (10-100 Myr prior to observation), followed by a recent (10 Myr)
upturn. This system is part of a candidate large-scale galaxy overdensity, with
an excess of Balmer-break galaxies compared to the field (3 $sigma$). We
discuss the possible origin of this nebula as material from a merger or gas
expelled by an active galactic nucleus (AGN). The symmetry of the nebula, its
bubble-like morphology, kinematics, high luminosity, and the extremely high
equivalent width of [OIII] together favour the AGN interpretation.
Intriguingly, there may be a physical connection between the presence of such a
large, luminous nebula and the possible metamorphosis of the central galaxy
towards quenching.
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