First detection of [CII]158 <i>μ</i>m at high redshift: vigorous star formation in the early universe

Abstract

We report the detection of the fine-structure line of at 157.74 in SDSS J114816.64+525150.3 (hereafter J1148+5251), the most distant known quasar, at , 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 (). The [Cii] line is detected at a significance level of 8σ and has a luminosity of . The ratio is , 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 ≈. The detection of in SDSS J1148+5251 suggests a significant enrichment of metals at (age of the universe ~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.