Abstract
We present cosmological radiation-hydrodynamic simulations, performed with
the code Ramses-RT, of radiatively-driven outflows in a massive quasar host
halo at z = 6. Our simulations include both single- and multi-scattered
radiation pressure on dust from a quasar and are compared against simulations
performed with thermal feedback. For radiation pressure-driving, we show that
there is a critical quasar luminosity above which a galactic outflow is
launched, set by the equilibrium of gravitational and radiation forces. While
this critical luminosity is unrealistically high in the single-scattering limit
for plausible black hole masses, it is in line with a 3 x 10^9 M_SUN black hole
accreting at its Eddington limit, if infrared (IR) multi-scattering radiation
pressure is included. The outflows are fast (v > 1000 km/s) and strongly
mass-loaded with peak mass outflow rates 10^3 - 10^4 M_SUN/yr, but short-lived
(< 10 Myr). Outflowing material is multi-phase, though predominantly composed
of cool gas, forming via a thermal instability in the shocked swept-up
component. Radiation pressure- and thermally-driven outflows both affect their
host galaxies profoundly, but in different, complementary ways.
Thermally-driven outflows couple more efficiently to diffuse halo gas,
generating more powerful, hotter and more volume-filling outflows. IR
radiation, through its ability to penetrate dense gas via diffusion, is more
efficient at ejecting gas from the bulge. The combination of gas ejection
through outflows with internal pressurisation by trapped IR radiation leads to
a complete shut down of star formation in the bulge. We hence argue that
radiation pressure-driven feedback may be a crucial ingredient in regulating
star formation in compact starbursts, especially during the quasar's
öbscured"' phase.
Description
[1709.08638] Quenching star formation with quasar outflows launched by trapped IR radiation
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