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Abstract
Supermassive black holes (SMBHs) are thought to be a key component of nearly every galaxy. These black holes, with masses 106 to 1010 M, dwell in the galactic center where they may power jets (Genzel et al., 2003; Falcke et al., 2004; Allen et al., 2006; Doeleman et al., 2012), regulate the energy in the interstellar medium (Cattaneo et al., 2009), and even transform the shape of the host galaxy (Gerhard & Binney, 1985; Norman, May, & van Albada, 1985; Merritt & Quinlan, 1998; Wachlin & Ferraz-Mello, 1998; Valluri & Merritt, 1998; Holley-Bockelmann et al., 2002). Despite playing such an integral role in galaxy evolution, how SMBHs form and evolve is a mystery. In general, most theoretical work on SMBH growth deals with how they evolve in mass from seed black holes in protogalaxies to supermassive ones today (Volonteri, Haardt, & Madau, 2003; Shapiro, 2005; King & Pringle, 2006; Lodato & Natarajan, 2006; Pelupessy et al., 2007). From these calculations, it is learned that SMBHs may grow rapidly during galaxy mergers; this process causes the black holes in each galaxy to sink to the center of the newly merged galaxy and coalesce. The merger process is violent and drives copious amounts of gas to the new galactic center, which provides new fuel to the black hole (Hernquist, 1989; Barnes & Hernquist, 1991; Mihos & Hernquist, 1994; Hernquist & Mihos, 1995; Barnes & Hernquist, 1996; Mihos & Hernquist, 1996; Hopkins et al., 2005). Through a combination of merger-driven gas accretion and direct coalescence it is possible that the remnants of the first stars may grow into the SMBHs of the current epoch (Volonteri, Haardt, & Madau, 2003; Volonteri et al., 2005; Volonteri & Rees, 2005).
