spectroscopically-confirmed $z\simeq6$ galaxy in the sample of @Finkelstein2015. The remaining 9 companion galaxies—surrounding five of our six quasars—have UV magnitudes and slopes consistent with those of star-forming galaxies at $z\simeq6$. The majority of these are brighter than $M^\ast$ [$-20.79$ mag at $z=6$, @Finkelstein2016 see Table \[tab:galaxy\_properties\]]. Unfortunately, existing observations at sub-mm to radio wavelengths do not resolve and/or detect the individual sources [e.g. @Wang2013], so morphological comparisons with existing data are not possible.

These 9 potential companion galaxies are separated from the quasars by $1\farcs4$–$3\farcs2$, corresponding to projected distances of 8.4–19.4 kpc. Simulations show that galaxies with companions at similar separations have higher AGN fractions [@McAlpine2020], and also enhanced star formation rates [@Patton2020]. This suggests that these companions, if their true 3D distance is of order their projected distance, could be interacting with the quasar host galaxies and may potentially have triggered or enhanced the observed AGN activity. However, tidal features from any such interaction would likely be rendered invisible due to the $(1+z)^4$ surface brightness dimming at $z\simeq6$.

We examine the relationship between size, Sérsic index and magnitude for these neighboring galaxies in Figure \[fig:3DHST\], in comparison to $z\simeq6$ galaxies in the CANDELS GOODS-South sample [@VanDerWel2012; @Brammer2012; @Skelton_2014; @Momcheva2016]. 