Feedback from active galactic nuclei: energy- versus momentum-driving
Abstract
We employ hydrodynamical simulations using the moving-mesh code AREPO to investigate the role of energy and momentum input from active galactic nuclei (AGN) in driving large-scale galactic outflows. We start by reproducing analytic solutions for both energy- and momentum-driven outflowing shells in simulations of a spherical isolated dark matter potential with gas in hydrostatic equilibrium and with no radiative cooling. We confirm that for this simplified setup, galactic outflows driven by a momentum input rate of order LEdd/c can establish an MBH-σ relation with slope and normalization similar to that observed. We show that momentum input at a rate of LEdd/c is however insufficient to drive efficient outflows once cooling and gas inflows as predicted by cosmological simulations at resolved scales are taken into account. We argue that observed large-scale AGN-driven outflows are instead likely to be energy-driven and show that such outflows can reach momentum fluxes exceeding 10LEdd/c within the innermost 10 kpc of the galaxy. The outflows are highly anisotropic, with outflow rates and a velocity structure found to be inadequately described by spherical outflow models. We verify that the hot energy-driven outflowing gas is expected to be strongly affected by metal-line cooling, leading to significant amounts ( ≳ 109 M⊙) of entrained cold gas.
- Publication:
-
Monthly Notices of the Royal Astronomical Society
- Pub Date:
- November 2014
- DOI:
- 10.1093/mnras/stu1632
- arXiv:
- arXiv:1406.2691
- Bibcode:
- 2014MNRAS.444.2355C
- Keywords:
-
- black hole physics;
- methods: numerical;
- cosmology: theory;
- Astrophysics - Astrophysics of Galaxies;
- Astrophysics - Cosmology and Nongalactic Astrophysics
- E-Print:
- 25 pages, 17 figures, 1 table, MNRAS (accepted in August 2014 after minor revisions)