Observing the interstellar medium (ISM) in z & 6 quasar host galaxies is essential for understanding the coevolution between the supermassive black holes and their hosts. To probe the gas physical conditions and search for imprints of active galactic nuclei (AGN) on the ISM, we report ALMA observations of the [N II]122µm and [O I]146µm lines and the underlying continuum from the z = 6.003 quasar SDSS J231038.88+185519.7. Together with previous [C II]158µm and [O III]88µm observations, we use the ratios of these fine-structure lines to probe the ISM properties. Similar to other high-z systems, this object exhibits a [C II]158µm/[O I]146µm ratio comparable to the lowest values found in local (Ultra)luminous infrared galaxies, suggesting a “warmer” and “denser” gas component compared to typical local systems. The [O III]88µm/[O I]146µm ratio is lower than that of other local and high-z systems, indicating a smaller ionized gas fraction in this quasar. The [O III]88µm/[N II]122µm ratio is comparable to that of local systems, and suggests a metallicity of Z/Z☉=1.5−2.1. Based on the [N II]122µm detection, we estimate that 17% of the [C II]158µm emission is associated with ionized gas. The [N II]122µm line shows a “flux deficit” comparable to local systems. The [O I]146µm line, with a [O I]146µm/FIR ratio >2× than expected from the local relation, indicates no [O I]146µm deficit. The low [C II]158µm/[O I]146µm ratio, together with the high [O I]146µm/FIR ratio in J2310+1855, reveals that the warm and dense gas is likely a result of AGN heating of the ISM.
|Original language||English (US)|
|State||Published - Jul 24 2020|
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