Detection of atomic carbon [C II] 158 μm and dust emission from A z = 7.1 quasar host galaxy

Abstract

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 × 109L , 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 L FIR = 5.8 × 1011-1.8 × 1012L is mainly powered by star formation, we derive a star formation rate in the range 160-440M 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 ± 15kms-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 × 1.7arcsec2 (corresponding to 10 × 9kpc2 at the redshift of J1120+0641). © 2012. The American Astronomical Society. All rights reserved..