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Radiative AGN feedback on a moving mesh: the impact of the galactic disc and dust physics on outflow properties. (arXiv:1812.01611v1 [astro-ph.GA])


Authors: David J. Barnes (1), Rahul Kannan (2), Mark Vogelsberger (1), Federico Marinacci (1,2) ((1) MIT, (2) Harvard/CfA)

Feedback from accreting supermassive black holes, active galactic nuclei
(AGN), is now a cornerstone of galaxy formation models. In this work, we
present radiation-hydrodynamic simulations of radiative AGN feedback using the
novel Arepo-RT. A central black hole emits radiation at a constant luminosity
and drives an outflow via radiation pressure on dust grains. Utilising an
isolated NFW halo we validate our setup in the single and multi-scattering
regimes, with the simulated shock front propagation in excellent agreement with
the expected analytic result. For a spherically symmetric NFW halo, an
examination of the simulated outflow properties generated by radiative feedback
demonstrates that they are lower than typically observed at a fixed AGN
luminosity, regardless of the collimation of the radiation. We then explore the
impact of a central disc galaxy and the assumed dust model on the outflow
properties. The contraction of the halo during the galaxy’s formation and
modelling the production of dust grains results in a factor $100$ increase in
the halo’s optical depth. Radiation is then able to couple momentum more
efficiently to the gas, driving a stronger shock and producing a mass-loaded
$sim10^{3},mathrm{M}_{odot},mathrm{yr}^{-1}$ outflow with a velocity of
$sim2000,mathrm{km},mathrm{s}^{-1}$, in agreement with observations.
However, the inclusion of dust destruction mechanisms, like thermal sputtering,
leads to the rapid destruction of dust grains within the outflow, reducing its
properties below typically observed values. We conclude that radiative AGN
feedback can drive outflows, but a thorough numerical and physical treatment is
required to assess its true impact.


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