Physical Constraints on the Extended Interstellar Medium of the z = 6.42 Quasar J1148+5251: [C ii]_{158 μm}, [N ii]_{205 μm}, and [O i]_{146 μm} Observations

<jats:title>Abstract</jats:title> <jats:p>We report new Northern Extended Millimeter Array observations of the [C <jats:sc>ii</jats:sc>]<jats:sub>158 <jats:italic>μ</jats:italic>m</jats:sub>, [N <jats:sc>ii</jats:sc>]<jats:sub>205 <jats:italic>μ</jats:italic>m</jats:sub>, and [O <jats:sc>i</jats:sc>]<jats:sub>146 <jats:italic>μ</jats:italic>m</jats:sub> atomic fine structure lines (FSLs) and dust continuum emission of J1148+5251, a <jats:italic>z</jats:italic> = 6.42 quasar, which probe the physical properties of its interstellar medium (ISM). The radially averaged [C <jats:sc>ii</jats:sc>]<jats:sub>158 <jats:italic>μ</jats:italic>m</jats:sub> and dust continuum emission have similar extensions (up to <jats:inline-formula> <jats:tex-math> <?CDATA $\theta ={2.51}_{-0.25}^{+0.46}\ \mathrm{arcsec}$?> </jats:tex-math> <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> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjac4e94ieqn1.gif" xlink:type="simple" /> </jats:inline-formula>, corresponding to <jats:inline-formula> <jats:tex-math> <?CDATA $r={9.8}_{-2.1}^{+3.3}\ \mathrm{kpc}$?> </jats:tex-math> <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> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjac4e94ieqn2.gif" xlink:type="simple" /> </jats:inline-formula>, accounting for beam convolution), confirming that J1148+5251 is the quasar with the largest [C <jats:sc>ii</jats:sc>]<jats:sub>158 <jats:italic>μ</jats:italic>m</jats:sub>-emitting reservoir known at these epochs. Moreover, if the [C <jats:sc>ii</jats:sc>]<jats:sub>158 <jats:italic>μ</jats:italic>m</jats:sub> emission is examined only along its NE–SW axis, a significant excess (>5.8<jats:italic>σ</jats:italic>) of [C <jats:sc>ii</jats:sc>]<jats:sub>158 <jats:italic>μ</jats:italic>m</jats:sub> 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 <jats:sc>ii</jats:sc>]<jats:sub>158 <jats:italic>μ</jats:italic>m</jats:sub> line wings that were reported in previous studies. We also report the first detection of the [O <jats:sc>i</jats:sc>]<jats:sub>146 <jats:italic>μ</jats:italic>m</jats:sub> and (tentatively) [N <jats:sc>ii</jats:sc>]<jats:sub>205 <jats:italic>μ</jats:italic>m</jats:sub> emission lines in J1148+5251. Using FSL ratios of the [C <jats:sc>ii</jats:sc>]<jats:sub>158 <jats:italic>μ</jats:italic>m</jats:sub>, [N <jats:sc>ii</jats:sc>]<jats:sub>205 <jats:italic>μ</jats:italic>m</jats:sub>, [O <jats:sc>i</jats:sc>]<jats:sub>146 <jats:italic>μ</jats:italic>m</jats:sub>, and previously measured [C <jats:sc>i</jats:sc>]<jats:sub>369 <jats:italic>μ</jats:italic>m</jats:sub> 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<jats:sup>3.5–4.5</jats:sup> <jats:italic>G</jats:italic> <jats:sub>0</jats:sub>), a high gas density (<jats:italic>n</jats:italic> ≃ 10<jats:sup>3.5–4.5</jats:sup> cm<jats:sup>−3</jats:sup>), and an H <jats:sc>i</jats:sc> column density of 10<jats:sup>23</jats:sup> cm<jats:sup>−2</jats:sup> reproduce the observed FSL ratios well.</jats:p>