We present a study of interstellar medium in the host galaxies of 9 QSOs at 0.1 < z < 0.2 with blackhole masses of 3 \times 10 ^ { 7 } M _ { \odot } to 3 \times 10 ^ { 9 } M _ { \odot } based on the far-IR spectroscopy taken with Herschel Space Observatory .
We detect the [ O i ] 63 \mu m ( [ C ii ] 158 \mu m ) emission in 6 ( 8 ) out of 8 ( 9 ) sources .
Our QSO sample has far-infrared luminosities ( L _ { FIR } ) \sim several times 10 ^ { 11 } L _ { \odot } .
The observed line-to- L _ { FIR } ratios ( L _ { [ O { \scriptsize \textsc { i } } ] 63 \mu { m } } / L _ { FIR } and L _ { [ C { \scriptsize \textsc { ii } } ] } / L _ { FIR } ) are in the ranges of 2.6 \times 10 ^ { -4 } - 10 ^ { -2 } and 2.8 \times 10 ^ { -4 } - 2 \times 10 ^ { -3 } respectively ( including upper limits ) .
These ratios are comparable to the values found in local ULIRGs , but higher than the average value published so far for z > 1 IR bright QSOs .
One target , W0752+19 , shows an additional broad velocity component ( \sim 720 km/s ) , and exceptionally strong [ O i ] 63 \mu m emission with L _ { [ O { \scriptsize \textsc { i } } ] 63 \mu { m } } / L _ { FIR } of 10 ^ { -2 } , an order of magnitude higher than that of average value found among local ( U ) LIRGs .
Combining with the analyses of the SDSS optical spectra , we conclude that the [ O i ] 63 \mu m emission in these QSOs is unlikely excited by shocks .
We infer that the broad [ O i ] 63 \mu m emission in W0752+19 could arise from the warm and dense ISM in the narrow line region of the central AGN .
Another possible explanation is the existence of a dense gas outflow with n _ { H } \sim 10 ^ { 4 } cm ^ { -3 } , where the corresponding broad [ C ii ] emission is suppressed .
Based on the far-IR [ O i ] and [ C ii ] line ratios , we estimate the constraints on the ISM density and UV radiation field intensity of n _ { H } \lesssim 10 ^ { 3.3 } cm ^ { -3 } and 10 ^ { 3 } < G _ { 0 } \lesssim 10 ^ { 4.2 } , respectively .
These values are consistent with those found in local Seyfert 1 ULIRGs .
In contrast , the gas with broad velocity width in W0752+19 has n _ { H } \gtrsim 10 ^ { 4.3 } cm ^ { -3 } and G _ { 0 } > 10 ^ { 4 } .