We investigate quasar outflows at z \geq 6 by performing zoom-in cosmological hydrodynamical simulations .
By employing the SPH code GADGET-3 , we zoom in the 2 R _ { 200 } region around a 2 \times 10 ^ { 12 } M _ { \odot } halo at z = 6 , inside a ( 500 ~ { } { Mpc } ) ^ { 3 } comoving volume .
We compare the results of our AGN runs with a control simulation in which only stellar/SN feedback is considered .
Seeding 10 ^ { 5 } M _ { \odot } BHs at the centers of 10 ^ { 9 } M _ { \odot } halos , we find the following results .
BHs accrete gas at the Eddington rate over z = 9 - 6 .
At z = 6 , our most-massive BH has grown to M _ { BH } = 4 \times 10 ^ { 9 } M _ { \odot } .
Fast ( v _ { r } > 1000 km/s ) , powerful ( \dot { M } _ { out } \sim 2000 M _ { \odot } /yr ) outflows of shock-heated low-density gas form at z \sim 7 , and propagate up to hundreds kpc .
Star-formation is quenched over z = 8 - 6 , and the total SFR ( SFR surface density near the galaxy center ) is reduced by a factor of 5 ( 1000 ) .
We analyse the relative contribution of multiple physical process : ( i ) disrupting cosmic filamentary cold gas inflows , ( ii ) reducing central gas density , ( iii ) ejecting gas outside the galaxy ; and find that AGN feedback has the following effects at z = 6 .
The inflowing gas mass fraction is reduced by \sim 12 \% , the high-density gas fraction is lowered by \sim 13 \% , and \sim 20 \% of the gas outflows at a speed larger than the escape velocity ( 500 km/s ) .
We conclude that quasar-host galaxies at z \geq 6 are accreting non-negligible amount of cosmic gas , nevertheless AGN feedback quenches their star formation dominantly by powerful outflows ejecting gas out of the host galaxy halo .