Far-infrared Properties of the Bright, Gravitationally Lensed Quasar J0439+1634 at z = 6.5

Abstract

We present IRAM NOrthern Extended Millimeter Array, James Clerk Maxwell Telescope/Submillimetre Common-User Bolometer Array-2 and Very Large Array (VLA) observations of the most distant known gravitationally lensed quasar, J0439+1634 at z = 6.5. We detect strong dust emission, [C II] 158 μm, [C I] 369 μm, [O I] 146 μm, CO(6-5), CO(7-6), CO(9-8), CO(10-9), H₂O 3_1,2-2_2,1, and H₂O 3_2,1-3_1,2 lines, as well as a weak radio continuum. The strong [C II] line yields a systemic redshift of the host galaxy to be z = 6.5188 ± 0.0002. The magnification makes J0439+1634 the far-infrared (FIR) brightest quasar at z > 6 known, with the brightest [C II] line yet detected at this redshift. The FIR luminosity is (3.4 ± 0.2) × 10¹³ μ ^-1 L _⊙, where μ ∼2.6-6.6 is the magnification of the host galaxy, estimated based on the lensing configuration from HST imaging. We estimate the dust mass to be (2.2 ± 0.1) × 10⁹ μ ^-1 {M}_⊙ . The CO spectral line energy distribution using four CO lines are best fit by a two-component model of the molecular gas excitation. The estimates of molecular gas mass derived from CO lines, and atomic carbon mass are consistent, in the range of (3.9-8.9) × 10¹⁰ μ ^-1 {M}_⊙ . The [C II]/[C I], [C II]/CO, and [O I]/[C II] line luminosity ratios suggest a photodissociation region model with more than one component. The ratio of H₂O 3_2,1-3_1,2 line luminosity to L _TIR is consistent with values in local and high-redshift ultra-/hyper-luminous infrared galaxies. The VLA observations reveal an unresolved radio continuum source, and indicate that J0439+1634 is a radio-quiet quasar with R = 0.05-0.17.