SIMBAD references

We report the nondetection of the [C II] (²P_3/2⟶²P_1/2) 157.74 µm transition in the z=6.42 quasar SDSS J1148+5251 after 37.5 hr of integration with the James Clerk Maxwell Telescope. This transition is the main cooling line of the star-forming interstellar medium and usually the brightest far-infrared (FIR) line in galaxies. Our observed 1 σ rms=1.3 mK in the T^*_Ascale translates to L_[CII]_<2.6x10⁹ L_☉. Using a recent estimate of the FIR continuum of this quasar, we derive for SDSS J1148+5251 L_[CII]_/L_FIR<5x10^–4, a ratio similar to that observed in local ultraluminous infrared galaxies but considerably smaller than what is typical in nearby normal and starburst galaxies. This indicates that the small L_[CII]/L_FIRratio observed locally in luminous FIR objects also persists at the highest redshifts.