Physical Constraints on the Extended Interstellar Medium of the z = 6.42 Quasar J1148+5251: [C ii]<sub>158 μm</sub>, [N ii]<sub>205 μm</sub>, and [O i]<sub>146 μm</sub> Observations
R. A. Meyer, Fabian Walter, C. Cicone, P. Cox, Roberto Decarli, R. Neri, Mladen Novak, Antonio Pensabene, Dominik A. Riechers, Axel Weiss
Abstract
Abstract We report new Northern Extended Millimeter Array observations of the [C ii ] 158 μ m , [N ii ] 205 μ m , and [O i ] 146 μ m atomic fine structure lines (FSLs) and dust continuum emission of J1148+5251, a z = 6.42 quasar, which probe the physical properties of its interstellar medium (ISM). The radially averaged [C ii ] 158 μ m and dust continuum emission have similar extensions (up to <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mi>θ</mml:mi> <mml:mo>=</mml:mo> <mml:msubsup> <mml:mrow> <mml:mn>2.51</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>−</mml:mo> <mml:mn>0.25</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>+</mml:mo> <mml:mn>0.46</mml:mn> </mml:mrow> </mml:msubsup> <mml:mspace width="0.33em"/> <mml:mi>arcsec</mml:mi> </mml:math> , corresponding to <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mi>r</mml:mi> <mml:mo>=</mml:mo> <mml:msubsup> <mml:mrow> <mml:mn>9.8</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>−</mml:mo> <mml:mn>2.1</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>+</mml:mo> <mml:mn>3.3</mml:mn> </mml:mrow> </mml:msubsup> <mml:mspace width="0.33em"/> <mml:mi>kpc</mml:mi> </mml:math> , accounting for beam convolution), confirming that J1148+5251 is the quasar with the largest [C ii ] 158 μ m -emitting reservoir known at these epochs. Moreover, if the [C ii ] 158 μ m emission is examined only along its NE–SW axis, a significant excess (>5.8 σ ) of [C ii ] 158 μ m emission (with respect to the dust) is detected. The new wide-bandwidth observations enable us to accurately constrain the continuum emission, and do not statistically require the presence of broad [C ii ] 158 μ m line wings that were reported in previous studies. We also report the first detection of the [O i ] 146 μ m and (tentatively) [N ii ] 205 μ m emission lines in J1148+5251. Using FSL ratios of the [C ii ] 158 μ m , [N ii ] 205 μ m , [O i ] 146 μ m , and previously measured [C i ] 369 μ m emission lines, we show that J1148+5251 has similar ISM conditions compared to lower-redshift (ultra)luminous infrared galaxies. CLOUDY modeling of the FSL ratios excludes X-ray-dominated regions and favors photodissociation regions as the origin of the FSL emission. We find that a high radiation field (10 3.5–4.5 G 0 ), a high gas density ( n ≃ 10 3.5–4.5 cm −3 ), and an H i column density of 10 23 cm −2 reproduce the observed FSL ratios well.