2017/07/10 by Paramita Barai, Simona Gallerani, Andrea Pallottini +5 · 1 citation
Physics and Astronomy · #astro-ph.GA #astro-ph.CO #astro-ph.HE
paper · pdf · doi:10.1093/mnras/stx2563
17 pages (excluding references and appendix), 11 figures, Submitted
arxiv created 2017/07/10 · arxiv updated 2017/12/06
We investigate quasar outflows at z ≥ 6 by performing zoom-in cosmological hydrodynamical simulations. By employing the SPH code GADGET-3, we zoom in the 2 R200 region around a 2 × 1012 M\odot halo at z = 6, inside a (500 ~ \rm 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 105 M\odot BHs at the centers of 109 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\rm BH = 4 × 109 M\odot. Fast (vr > 1000 km/s), powerful (M\rm out ∼ 2000 M\odot/yr) outflows of shock-heated low-density gas form at z ∼ 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 ∼ 12 %, the high-density gas fraction is lowered by ∼ 13 %, and ∼ 20 % of the gas outflows at a speed larger than the escape velocity (500 km/s). We conclude that quasar-host galaxies at z ≥ 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.