The Decoupled Kinematics of high-z QSO Host Galaxies and their Lya halos
  We present a comparison of the interstellar medium traced by [CII] (ALMA),
and ionised halo gas traced by Lya (MUSE), in and around QSO host galaxies at
z~6. To date, 18 QSOs at this redshift have been studied with both MUSE and
high-resolution ALMA imaging; of these, 8 objects display a Lya halo. Using
datacubes matched in velocity resolution, we compare and contrast the spatial
and kinematic information of the Lya halos and the host galaxies' [CII] (and
dust-continuum) emission. We find that the Lya halos extend typically 3-30
times beyond the interstellar medium of the host galaxies. The majority of the
Lya halos do not show ordered motion in their velocity fields, whereas most of
the [CII] velocity fields do. In those cases where a velocity gradient can be
measured in Lya, the kinematics do not align with those derived from the [CII]
emission. This implies that the Lya emission is not tracing the outskirts of a
large rotating disk that is a simple extension of the central galaxy seen in
[CII] emission. It rather suggests that the kinematics of the halo gas are
decoupled from those of the central galaxy. Given the scattering nature of Lya,
these results need to be confirmed with JWST IFU observations that can
constrain the halo kinematics further using the non-resonant Ha line.
