2002AJ....123.1288W

We report upper limits on CO J=2-1 and J=5-4 emission from the quasar SDSSp J104433.04-012502.2, at z=5.73, from observations made with the Berkeley-Illinois-Maryland Association array. Previously reported limits on CO J=6-5 emission were obtained at z=5.80, which is now thought to be off by 1%, and the observations likely missed the relevant redshifts for molecular gas. The new 3 σ upper limits on the line luminosities are L'_CO(2-1)<5.1x10¹⁰ K km.s^–1 pc² and L'_CO(5-4)<3.0x10¹⁰ K km.s^–1 pc², assuming 200 km.s^–1 line width. The CO J=5-4 observations place an upper limit on warm, dense molecular gas mass comparable to amounts derived for some other high-redshift quasar systems from detections of this line. The limit on CO J=2-1 emission suggests that excitation bias does not affect this conclusion. In addition, no companion galaxies rich in molecular gas are found in a ∼1.4 Mpc field surrounding the quasar.