Search for Molecular Gas in the quasar SDSS 1044-0125 at z=5.73

Abstract

We report upper limits on CO J=2--1 and CO 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 (Iwata et al. 2001) 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 $3\sigma$ upper limits on the line luminosities are $L^{'}_{CO}(2-1) < 5.1 \times 10^{10}$ K km s$^{-1}$ pc$^2$ and $L^{'}_{CO}(5-4) < 3.0 \times 10^{10}$ K km s$^{-1}$ pc$^2$, assuming 200 km s$^{-1}$ linewidth. 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 molecular gas rich companion galaxies are found in a $\sim1.4$ Mpc field surrounding the quasar.