DETECTION OF ATOMIC CARBON [C ii] 158 μm AND DUST EMISSION FROM A z = 7.1 QUASAR HOST GALAXY

Using the IRAM Plateau de Bure Interferometer, we report the detection of the 158 μm [C ii] emission line and underlying dust continuum in the host galaxy of the quasar ULAS J112001.48+064124.3 (hereafter J1120+0641) at z = 7.0842 ± 0.0004. This is the highest redshift detection of the [C ii] line to date, and allows us to put the first constraints on the physical properties of the host galaxy of J1120+0641. The [C ii] line luminosity is 1.2  ±  0.2 × 109 L☉, which is a factor ∼4 lower than observed in a luminous quasar at z = 6.42 (SDSS J1148+5251). The underlying far-infrared (FIR) continuum has a flux density of 0.61 ± 0.16 mJy, similar to the average flux density of z ∼ 6 quasars that were not individually detected in the rest-frame FIR. Assuming that the FIR luminosity of LFIR = 5.8 × 1011–1.8 × 1012 L☉ is mainly powered by star formation, we derive a star formation rate in the range 160–440 M☉ yr−1 and a total dust mass in the host galaxy of 6.7 × 107–5.7 × 108 M☉ (both numbers have significant uncertainties given the unknown nature of dust at these redshifts). The [C ii] line width of σV = 100 ± 15 km s−1 is among the smallest observed when compared to the molecular line widths detected in z ∼ 6 quasars. Both the [C ii] and dust continuum emission are spatially unresolved at the current angular resolution of 2.0 × 1.7 arcsec2 (corresponding to 10 × 9 kpc2 at the redshift of J1120+0641).