The Growth of the Stellar Seeds of Supermassive Black Holes

Jarrett Johnson (LANL, MPE)

with

Bhaskar Agarwal (MPE), Claudio Dalla Vecchia (MPE), Fabrice Durier

(Victoria,MPE), Chris Fryer (LANL), Thomas Greif (MPA), Sadegh Khochfar (MPE), Hui Li

(LANL), and Dan Whalen (CMU, LANL)

Rapid Black Hole Growth in the Early Universe

How massive can Pop III stellar BH seeds become?

Observed quasars with 109 Msun black holes at z > 6

Pop III stars collapsed to form BH seeds at z > 10

credit: firstgalaxies.org

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)

• A ~ 107 Msun 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)

JLJ, Khochfar, Greif & Durier 2011

Gas temperature

• Gas collapses and accretes onto central supermassive star at

~ 0.1 – 1 Msun yr-1

Modeling Accretion onto Supermassive Stars

JLJ, Whalen, Fryer & Li 2012; see also Omukai & Inutsuka 2002, Hosokawa et al. 2012

• 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

H II regionSupersonic Free fall

The Maximum Stellar Mass

JLJ, Whalen, Fryer & Li 2012

Range of possible stellar masses

Cosmological simulations suggest final SMS masses of 105 – 106 Msun

Supermassive Star Formation in the FiBY• The First Billion Years

project (FiBY; Khochfar et 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

JLJ, Dalla Vecchia & Khochfar 2012

• 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)

Supermassive Star Formation is Common!

The high LW fluxes required for SMS and direct collapse BH formation are present, even in our (4 Mpc)3 simulation volume

JLJ, Dalla Vecchia & Khochfar 2012; see also Agarwal et al. 2012, Hummel et al. 2012, Petri et al. 2012

Supermassive stars may be more common than previously thought

Supermassive Star Formation is Common!

Agarwal, Khochfar, JLJ, et al. 2012

Many supermassive stars may be found in deep surveys by the JWST!

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

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

JLJ, Whalen, Fryer & Li 2012

• These signatures could be detected by the James Webb Space Telescope (JWST)

Conclusions

• The observational signatures of rapidly accreting supermassive stars may detectable by the JWST

• Supermassive stars (> 104 Msun) 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 ~105 Msun 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