CO (2-1) Line Emission in Redshift 6 Quasar Host Galaxies
  We report new observations of CO (2-1) line emission toward five z~6 quasars
using the Ka-band receiver system on the Expanded Very Large Array (EVLA).
Strong detections were obtained in two of them, SDSS J092721.82+200123.7 and
CFHQS J142952.17+544717.6, and a marginal detection was obtained in another
source, SDSS J084035.09+562419.9. Upper limits of the CO (2-1) line emission
have been obtained for the other two objects. The CO (2-1) line detection in
J0927+2001, together with previous measurements of the CO (6-5) and (5-4)
lines, reveals important constraints on the CO excitation in the central ~10
kpc region of the quasar host galaxy. The CO (2-1) line emission from
J1429+5447 is resolved into two distinct peaks separated by 1.2" (~6.9 kpc),
indicating a possible gas-rich, major merging system, and the optical quasar
position is consistent with the west peak. This result is in good agreement
with the picture in which intense host galaxy star formation is coeval with
rapid supermassive black hole accretion in the most distant universe. The two
EVLA detections are ideal targets for further high-resolution imaging (e.g.,
with ALMA or EVLA observations) to study the gas distribution, dynamics, and
SMBH-bulge mass relation in these earliest quasar-host galaxy systems.
