Ly$\alpha$ Halos Around $z\sim6$ Quasars
  We present deep MUSE observations of five quasars within the first Gyr of the
Universe ($z\gtrsim6$), four of which display extended Ly$\alpha$ halos. After
PSF-subtraction, we reveal halos surrounding two quasars for the first time, as
well as confirming the presence of two more halos for which tentative
detections exist in long-slit spectroscopic observations and narrow-band
imaging. The four Ly$\alpha$ halos presented here are diverse in morphology and
size, they each display spatial asymmetry, and none are centred on the position
of the quasar. Spectra of the diffuse halos demonstrate that none are
dramatically offset in velocity from the systemic redshift of the quasars
($\Delta$ v $< 200$ kms$^{-1}$), however each halo shows a broad Ly$\alpha$
line, with a velocity width of order $\sim1000$ kms$^{-1}$. Total Ly$\alpha$
luminosities range between $\sim$ $2 \times 10^{43}$ erg s$^{-1}$ and $\sim$ $2
\times 10^{44}$ erg s$^{-1}$, reaching maximum radial extents of $13 - 30$ pkpc
from the quasar positions. We find larger sizes and higher Ly$\alpha$
luminosities than previous literature results at this redshift, but find no
correlation between the quasar properties and the Ly$\alpha$ halo, suggesting
that the detected emission is most closely related to the physical properties
of the circum-galactic medium
