SIMBAD references

Recent X-ray observations of hot gas in the galaxy cluster MS 0735.6+7421 reveal huge radio-bright, quasi-bipolar X-ray cavities having a total energy ∼10⁶² erg, the most energetic active galactic nucleus (AGN) outburst currently known. We investigate the evolution of this outburst with two-dimensional axisymmetric gas dynamical calculations in which the cavities are inflated by relativistic cosmic rays (CRs). Many key observational features of the cavities and associated shocks are successfully reproduced. The radial elongation of the cavities indicates that CRs were injected into the cluster gas by a (jet) source moving out from the central AGN. AGN jets of this magnitude must be almost perfectly identically bipolar. The relativistic momentum of a single jet would cause a central AGN black hole of mass 10⁹ M_☉ to recoil at ∼6000 km/s, exceeding kick velocities during black hole mergers, and be ejected from the cluster-center galaxy. Observed deviations from bipolar symmetry in the radio cavities can be caused by subsonic flows in the ambient cluster gas, but reflection shocks between symmetric cavities are likely to be visible in deep X-ray images. When the cavity inflation is complete, 4PV underestimates the total energy received by the cluster gas. Deviations of the cluster gas from hydrostatic equilibrium are most pronounced during the early cavity evolution when the integrated cluster mass found from the observed gas pressure gradient can have systematic errors near the cavities of ∼10%-30%. The creation of the cavity with CRs generates a long-lasting global cluster expansion that reduces the total gas thermal energy below that received from the cavity shock–even this most energetic AGN event has a net cooling effect on cluster gas. One gigayear after this single outburst, a gas mass of ∼6x10¹¹ M_☉ is transported out beyond a cluster radius of 500 kpc. Such post-cavity outflows can naturally produce the discrepancy observed between the cluster gas mass fraction and the universal baryon fraction inferred from Wilkinson Microwave Anisotropy Probe observations.