CO observations of a FeLoBAL Quasar with an Ha absorption line at z=2.3

SDSS J083942.11+380526.3 is an Iron Low-ionization Broad Absorption Line (FeLoBAL) quasar at z = 2.3, and Aoki et al. (2006) recently found the presence of an Hα absorption line in the broad Hα emission line. Motivated by an idea that this quasar may be a huge molecular gas reservoir in the early phase of quasar evolution, we made CO(J = 3-2) observations of it using the Nobeyama Millimeter Array. No significant CO emission was detected; although an emission-like feature (2.5σ) was seen close (∼ 2″) to the quasar, we regard it as noise. The obtained 3σ upper limit on the CO luminosity is L_CO(J=3-2)′ = 4.5 × 10¹⁰ K km s^-1 pc², which corresponds to M(H₂) = 3.6 × 10¹⁰M_⊙ if we adopt CO-to-H₂ conversion factor of 0.8 M_⊙ (K km s^_1 pc ²)^-1. This upper limit is comparable to L _CO(J=3-2)′ (and thus the molecular gas mass) detected in quasars and BAL quasars at z= 1-3, and no sign of the presence of the huge amount of molecular gas in this FeLoBAL quasar was obtained.