Super-Eddington accretion and feedback from the first massive seed black holes

Abstract

Super-Eddington accretion onto massive black hole seeds may be commonplace in\nthe early Universe, where the conditions exist for rapid accretion. Direct\ncollapse black holes are often invoked as a possible solution to the\nobservation of super massive black holes (SMBHs) in the pre-reionisation\nUniverse. We investigate here how feedback, mainly in the form of bipolar jets,\nfrom super-Eddington accreting seed black holes will affect their subsequent\ngrowth. We find that, nearly independent of the mass loading of the bipolar\njets, the violent outflows generated by the jets evacuate a region of\napproximately 0.1 pc surrounding the black hole seed. However, the jet outflows\nare unable to break free of the halo and their impact is limited to the\nimmediate vicinity of the black hole. The outflows suppress any accretion for\napproximately a dynamical time. The gas then cools, recombines and falls back\nto the centre where high accretion rates are again observed. The overall effect\nis to create an effective accretion rate with values of between 0.1 and 0.5\ntimes the Eddington rate. If this episodic accretion rate is maintained for\norder 500 million years then the black hole will increase in mass by a factor\nof between 3 and 300 but far short of the factor of $10^4$ required for the\nseeds to become the SMBHs observed at $z>6$. Therefore, direct collapse black\nholes born into atomic cooling haloes and which experience strong negative\nmechanical feedback will require external influences (e.g. rapid major mergers\nwith other haloes) to promote efficient accretion and reach SMBH masses within\na few hundred million years.\n