2007/03/31 by Tamara Bogdanović, Tamara Bogdanovic, Christopher S. Reynolds +1 · 8 citations
Physics and Astronomy · #Astrophysical Phenomena and Observations #Galaxies: Formation, Evolution, Phenomena #Pulsars and Gravitational Waves Research #astro-ph #gr-qc
paper · pdf · doi:10.1086/518769
referee's comments included, to appear in ApJL
arxiv created 2007/04/12 · openalex publication_date 2007/05/14 · arxiv updated 2009/12/01 · openalex created_date 2016/06/24 · openalex updated_date 2026/07/31
Recent numerical relativistic simulations of black hole coalescence suggest that in certain alignments the emission of gravitational radiation can produce a kick of several thousand kilometers per second. This exceeds galactic escape speeds; hence, unless there is a mechanism to prevent this, one would expect many galaxies that had merged to be without a central black hole. Here we show that in most galactic mergers, torques from accreting gas suffice to align the orbit and spins of both black holes with the large-scale gas flow. Such a configuration has a maximum kick speed <200 km s -1 , safely below galactic escape speeds. We predict, however, that in mergers of galaxies without much gas, the remnant will be kicked out several percent of the time. We also discuss other predictions of our scenario, including implications for jet alignment angles and X-type radio sources.