Spectroscopy of the spatially-extended Lya emission around a QSO at
  z=6.4
  We have taken a deep, moderate-resolution Keck/Deimos spectra of QSO,
CFHQS2329, at z=6.4. At the wavelength of Lya, the spectrum shows a
spatially-extended component, which is significantly more extended than a
stellar spectrum, and also a continuum part of the spectrum. The restframe line
width of the extended component is 21+-7 A, and thus smaller than that of QSO
(52+-4 A), where they should be identical if the light is incomplete
subtraction of the QSO component. Therefore, these comparisons argue for the
detection of a spatially extended Lya nebulae around this QSO. This is the
first z>6 QSO that an extended Lya halo has been observed around. Careful
subtraction of the central QSO spectrum reveals a lower limit to the Lya
luminosity of (1.7+-0.1)x 10^43 erg s^-1. This emission may be from the
theoretically predicted infalling gas in the process of forming a primordial
galaxy that is ionized by a central QSO. On the other hand, if it is
photoionized by the host galaxy, an estimated star-formation rate of >3.0 Msun
yr^-1 is required.
  If we assume the gas is virialized, we obtain dynamical mass estimate of
Mdyn=1.2x10^12 Msun. The derived MBH/Mhost is 2.1x10^-4, which is two orders
smaller than those from more massive z~6 QSOs, and places this galaxy in
accordance with the local M-sigma relation, in contrast to a previous claim on
the evolution of M-sigma relation at z~6. We do not claim evolution or
non-evolution of the M-sigma relation based on a single object, but our result
highlights the importance of investigating fainter QSOs at z~6.
