Abstract
Measuring the spins of supermassive black holes (SMBHs) in active galactic nuclei (AGN) can inform us about the relative role of gas accretion vs. mergers in recent epochs of the life of the host galaxy and its AGN. Recent theoretical and observation advances have enabled spin measurements for ten SMBHs thus far, but this science is still very much in its infancy. Herein, I discuss how we measure black hole spin in AGN, using recent results from a long Suzaku campaign on NGC 3783 to illustrate this process and its caveats. I then present our current knowledge of the distribution of SMBH spins in the local universe. I also address prospects for improving the accuracy, precision and quantity of these spin constraints in the next decade and beyond with instruments such as NuSTAR, Astro-H and future large-area X-ray telescopes.
Highlights
Measurements of the spins of supermassive black holes (SMBHs) in active galactic nuclei (AGN) can contribute to the understanding of these complex and energetic environments in three principal ways: They offer a rare probe of the nature of the spacetime proximal to the event horizon of the black hole (BH), well within the strong-field gravity regime [12, 19]; They can shed light on the relation of a black hole’s angular momentum to its outflow power in the form of winds and jets
In the previous two sections we have noted the importance of both adequate data and a physically self-consistent modeling approach to constraining SMBH spins in AGN
We have stressed the importance of one very critical assumption that must be made in order to calculate BH spin: namely, that the inner edge of the accretion disk is at the innermost stable circular orbit (ISCO)
Summary
Measurements of the spins of supermassive black holes (SMBHs) in active galactic nuclei (AGN) can contribute to the understanding of these complex and energetic environments in three principal ways:. They can inform us about the relative role of gas accretion vs mergers in recent epochs of the life of the host galaxy and its AGN [3] For these reasons, developing a theoretical and observation framework in which to measure black hole spin accurately and precisely is of critical importance to our understanding of how galaxies form and evolve over cosmic time. J is the BH angular momentum, G is Newton’s constant and M is the mass of the BH) is known to within Δa ≤ 10%, meaningful correlations between spin and other environmental variables (e.g., jet power, history of the accretion flow) can be drawn In this proceeding, I discuss our current knowledge of the distribution of SMBH spins in the local universe and future directions of BH spin research.
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