A 100 kpc nebula associated with the "Teacup" fading quasar
  We report the discovery of a ~100 kpc ionized nebula associated with the
radio quiet type 2 quasar (QSO2) nicknamed the "Teacup" (z=0.085). The giant
nebula is among the largest known around active galaxies at any z. We propose
that it is part of the circumgalactic medium (CGM) of the QSO2 host, which has
been populated with tidal debris by galactic interactions. This rich gaseous
medium has been rendered visible due to the illumination by the powerful active
nucleus (AGN). Subsolar abundances (~0.5Z(sun)) are tentatively favored by AGN
photoionization models. We also report the detection of coronal emission (Fe+6)
from the NE bubble, at ~9 kpc from the AGN. The detection of coronal lines at
such large distances from the AGN and the [NII]/Halpha, [SII]/Halpha,
[OI]/Halpha optical emission line ratios of the giant nebula are consistent
with the fading quasar scenario proposed by Gagne et al. (2014). The fading
rate appears to have been faster in the last ~46,000 yr. Deep wide field
integral field spectroscopy of giant nebulae around powerful AGN such as the
"Teacup's" with instruments such as MUSE on VLT opens up a way to detect and
study the elusive material from the CGM around massive active galaxies thanks
to the illumination by the luminous AGN.
