First detection of [CII]158 μm at high redshift:: vigorous star formation in the early universe

We report the detection of the P-2(3/2) -> P-2(1/2) fine-structure line of C+ at 157.74 mu m in SDSS J114816.64+525150.3 ( hereafter J1148+5251), the most distant known quasar, at z = 6.42, using the IRAM 30-m telescope. This is the first detection of the [CII] line at high redshift, and also the first detection in a Hyperluminous Infrared Galaxy (L-FIR > 10(13) L-circle dot). The [CII] line is detected at a significance level of 8 sigma and has a luminosity of 4.4 x 10(9) L-circle dot. The [CII]/FIR ratio is 2 x 10(-4), about an order, of magnitude smaller than observed in local normal galaxies and similar to the ratio observed in local Ultraluminous Infrared Galaxies. The [CII] line luminosity indicates that the host galaxy of this quasar is undergoing an intense burst of star formation with an estimated rate of approximate to 3000 M-circle dot yr(-1). The detection of C+ in SDSS J1148+ 5251 suggests a significant enrichment of metals at z similar to 6 (age of the universe similar to 870 Myr), although the data are consistent with a reduced carbon to oxygen ratio as expected from chemical evolutionary models of the early phases of galaxy formation.