The Growth of the Stellar Seeds of Supermassive Black Holes

1. The Growth of the Stellar Seeds of Supermassive Black Holes Jarrett Johnson (LANL, MPE) with BhaskarAgarwal (MPE), Claudio DallaVecchia (MPE), FabriceDurier(Victoria,MPE), Chris Fryer (LANL), Thomas Greif (MPA), SadeghKhochfar (MPE), Hui Li (LANL), and Dan Whalen (CMU, LANL)

2. Rapid Black Hole Growth in the Early Universe Observed quasars with 109Msun black holes at z > 6 Pop III stars collapsed to form BH seeds at z > 10 How massive can Pop III stellar BH seeds become? credit: firstgalaxies.org

3. Supermassive Star Formation in the First Galaxies • An elevated H2-dissociating radiation field suppresses cooling and fragmentation of primordial gas (e.g. Machacek et al. 2001; Yoshida et al. 2003; O’Shea & Norman 2008; Omukai et al. 2008; but see also Inayoshi & Omukai 2012) Gas temperature • A ~ 107Msun halo forms at z ~ 15 with Tvir ~ 104 K and cooling only by collisional excitation of hydrogen (e.g. Bromm & Loeb 2003; Spaans & Silk 2006; Begelman et al. 2006; Wise et al. 2008; Regan & Haehnelt 2009; Shang et al. 2010) • Gas collapses and accretes onto central supermassive star at • ~ 0.1 – 1 Msun yr-1 JLJ, Khochfar, Greif & Durier 2011

4. Modeling Accretion onto Supermassive Stars Supersonic Free fall H II region • Model accretion flow in spherical symmetry and solve for minimum possible steady-state accretion rate • Include radiative feedback on the accreting gas due to photoionization pressure JLJ, Whalen, Fryer & Li 2012; see also Omukai & Inutsuka 2002, Hosokawa et al. 2012

5. The Maximum Stellar Mass Range of possible stellar masses Cosmological simulations suggest final SMS masses of 105 – 106Msun JLJ, Whalen, Fryer & Li 2012

6. Supermassive Star Formation in the FiBY • The First Billion Years project (FiBY; Khochfaret al. 2012) • Large-scale cosmological simulations including SN feedback and metal enrichment, LW radiation from individual (Pop II and III) star clusters, and reionization feedback • Check for primordial halos subjected to high LW flux (e.g. Bromm & Loeb 2003; Dijkstra et al. 2008; Ahn et al. 2009; Shang et al. 2010; Wolcott-Green et al. 2011; Petri et al. 2012): • - J21 > 30 (Pop II sources) • - J21 > 103 (Pop III sources) JLJ, DallaVecchia & Khochfar 2012

7. Supermassive Star Formation is Common! Supermassive stars may be more common than previously thought The high LW fluxes required for SMS and direct collapse BH formation are present, even in our (4 Mpc)3 simulation volume JLJ, DallaVecchia & Khochfar 2012; see also Agarwal et al. 2012, Hummel et al. 2012, Petri et al. 2012

8. Supermassive Star Formation is Common! Model LW feedback from both Pop II and III star-forming halos: - Vary the LW photon escape fraction (e.g. Ricotti et al. 2001; Kitayama et al. 2004) - Vary the star formation efficiency - Account for photoheating during reionization Many supermassive stars may be found in deep surveys by the JWST! Agarwal, Khochfar, JLJ, et al. 2012

9. Observational Signatures of Supermassive Stars • Observable signatures of rapidly accreting supermassive stars: • (1) No Lya emission • (2) Elevated luminosity in Balmer series lines (Ha) • (3) Strong He II l1640 emission • (4) Strong stellar+nebular continuum emission below the Lyman limit • These signatures could be detected by the James Webb Space Telescope (JWST) JLJ, Whalen, Fryer & Li 2012

10. Conclusions • Supermassive stars (> 104Msun) formed in primordial protogalaxies are strong candidates for the seeds of observed supermassive black holes • The strong ionizing radiation emitted from supermassive primordial stars sets their maximum mass to ~105Msun for accretion rates of ~ 0.1 Msun yr-1 • The conditions for SMS formation are much more common than previously thought – could be the seeds of most supermassive black holes today • The observational signatures of rapidly accreting supermassive stars may detectable by the JWST