Heating the Intra Cluster Medium by Jets Through Mixing and Inflation of Bubbles

TYPEAstrophysics Seminar
Speaker:Avishai Gilkis
Location:Lidow 620

The radiative cooling time of the intra cluster medium (ICM) at the centres of many galaxy clusters are much shorter than their ages. Therefore, the ICM hot atmospheres are expected to cool and to form stars. Cold gas and star formation are observed in central cluster galaxies but at levels below those expected from an unimpeded cooling flow. It is widely accepted that a negative feedback heating mechanism offsets cooling to some degree, but the exact details remain unclear. In our work, we show that mixing of high entropy shocked jet’s material with the ICM is a major heating process, along as well as perpendicular, to the jets’ axis. Heating by the forward shock is not significant. We do this by simulating jet-inflated bubbles in cooling flows with the PLUTO hydrodynamic code, and analyzing in detail the resulting thermal evolution of the ICM. We find that the mixing is very efficient in heating the ICM in all directions, to distances of ~10 kpc and more. Although the jets are active for a relatively short time period, the mixing and heating near the equatorial plane, as well as along the symmetry axis, continue to counter radiative cooling for a long period after the jets activity has ceased.