AGN effect on cooling flow dynamics

Monthly Notices of the Royal Astronomical Society

2009

We show that repeated sound waves in the intracluster medium (ICM) can be excited by a single inflation episode of an opposite bubble pair. To reproduce this behaviour in numerical simulations, the bubbles should be inflated by jets, rather than being injected artificially as already full‐blown bubbles. The multiple sound waves are excited by the motion of the bubble–ICM boundary that is caused by vortices inside the inflated bubbles and the backflow (‘cocoon’) of the ICM around the bubble. These sound waves form a structure that can account for the ripples observed in the Perseus cooling flow cluster. We inflate the bubbles using slow massive jets either with a very wide opening angle or that are narrow and precessing. The wide jets (or collimated fast winds) are slow in the sense that they are highly subrelativistic, vj∼ 0.01c– 0.1c, and they are massive in the sense that the pair of bubbles carries back to the ICM a large fraction of the cooling mass, i.e. ∼1–50 M⊙ yr−1. We use a two‐dimensional axisymmetric (referred to as 2.5D) hydrodynamical numerical code (vh‐1).

Section: Introductionsupporting

confidence: 82%

Sound waves excitation by jet-inflated bubbles in clusters of galaxies

Sternberg

Monthly Notices of the Royal Astronomical Society

2009

“…If the jets penetrate to a too large distance, then no bubbles are formed, while in intermediate cases elongated and/or detached from the centre bubbles are formed (e.g. Basson & Alexander ; Omma et al ; Heinz et al ; Vernaleo & Reynolds ; Alouani Bibi et al ; Sternberg et al ; O'Neill & Jones ; Mendygral, O'Neill & Jones ; Mendygral et al ).…”

Section: Introductionmentioning

confidence: 99%

Heating the intra-cluster medium perpendicular to the jets axis

Gilkis

Monthly Notices of the Royal Astronomical Society

2012

Jets from supermassive black holes in the centres of galaxy clusters are a potential candidate for moderating gas cooling and subsequent star formation through depositing energy in the intra-cluster gas. In this work, we simulate the jet-intra-cluster medium interaction using the moving-mesh magnetohydrodynamics code Arepo. Our model injects supersonic, low density, collimated and magnetised outflows in cluster centres, which are then stopped by the surrounding gas, thermalise and inflate low-density cavities filled with cosmic-rays. We perform high-resolution, non-radiative simulations of the lobe creation, expansion and disruption, and find that its dynamical evolution is in qualitative agreement with simulations of idealised low-density cavities that are dominated by a large-scale Rayleigh-Taylor instability. The buoyant rising of the lobe does not create energetically significant small-scale chaotic motion in a volume-filling fashion, but rather a systematic upward motion in the wake of the lobe and a corresponding back-flow perpendicular to it. We find that, overall, 50 per cent of the injected energy ends up in material which is not part of the lobe, and about 25 per cent remains in the inner 100 kpc. We conclude that jet-inflated, buoyantly rising cavities drive systematic gas motions which play an important role in heating the central regions, while mixing of lobe material is subdominant. Encouragingly, the main mechanisms responsible for this energy deposition can be modelled already at resolutions within reach in future, high-resolution cosmological simulations of galaxy clusters.

“…We used slow massive jets, as have been used before in a number of numerical studies (e.g. Paper I; Alouani Bibi et al 2007). We further discuss the usage of slow massive jets in .…”

Section: Numerical Methods and Set‐upmentioning

confidence: 99%

“…In recent years, two‐ and three‐dimensional hydrodynamical simulations of jets and bubbles in clusters of galaxies were conducted to study different aspects of their interaction with the ICM, such as heating the ICM (e.g. Basson & Alexander 2003; Heinz & Churazov 2005; Reynolds et al 2005; Heinz et al 2006; Vernaleo & Reynolds 2006; Alouani Bibi et al 2007; Binney, Alouani Bibi & Omma 2007; Brüggen et al 2007; Ruszkowski et al 2007). In our studies, we aim to understand the conditions leading to the formation of fat bubbles.…”

Section: Introductionmentioning

confidence: 99%

Inflating fat bubbles in clusters of galaxies by precessing massive slow jets

Sternberg

2008

Monthly Notices RAS

We conduct hydrodynamical numerical simulations and find that precessing massive slow jets can inflate fat bubbles, that is, more‐ or less‐spherical bubbles, that are attached to the centre of clusters of galaxies. To inflate a fat bubble, the jet should precess fast. The precessing angle θ should be large, or change over a large range 0 ≤θ≤θmax∼ 30°–70° (depending also on other parameters), where θ= 0° is the symmetry axis. The constraints on the velocity and mass‐outflow rate are similar to those on wide jets to inflate fat bubbles. The velocity should be vj∼ 104 km s−1, and the mass‐loss rate of the two jets should be . These results, and our results from a previous paper dealing with slow wide jets, support the claim that a large fraction of the feedback heating in cooling flow clusters and in the processes of galaxy formation is done by slow massive jets.