Observing the interstellar medium ( ISM ) in z \gtrsim 6 quasars host galaxies is essential for understanding the co-evolution 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 [ \ion N2 ] _ { 122 \mu m } and [ \ion O1 ] _ { 146 \mu m } lines and the underlying continuum from the z = 6.003 quasar SDSS J231038.88+185519.7 .
Together with previous [ \ion C2 ] _ { 158 \mu m } and [ \ion O3 ] _ { 88 \mu m } 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 [ \ion C2 ] _ { 158 \mu m } / [ \ion O1 ] _ { 146 \mu m } 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 [ \ion O3 ] _ { 88 \mu m } / [ \ion O1 ] _ { 146 \mu m } ratio is lower than that of other local and high- z systems , indicating a smaller ionized gas fraction in this quasar .
The [ \ion O3 ] _ { 88 \mu m } / [ \ion N2 ] _ { 122 \mu m } ratio is comparable to that of local systems , and suggests a metallicity of Z / Z _ { \sun } =1.5 - 2.1 .
Based on the [ \ion N2 ] _ { 122 \mu m } detection , we estimate that 17 \% of the [ \ion C2 ] _ { 158 \mu m } emission is associated with ionized gas .
The [ \ion N2 ] _ { 122 \mu m } line shows a “ flux deficit ’ comparable to local systems .
The [ \ion O1 ] _ { 146 \mu m } line , with a [ \ion O1 ] _ { 146 \mu m } /FIR ratio \textgreater 2 \times than expected from the local relation , indicates no [ \ion O1 ] _ { 146 \mu m } deficit .
The low [ \ion C2 ] _ { 158 \mu m } / [ \ion O1 ] _ { 146 \mu m } ratio , together with the high [ \ion O1 ] _ { 146 \mu m } /FIR ratio in J2310+1855 , reveals that the warm and dense gas is likely a result of AGN heating to the ISM .