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Supermassive Black Hole Growth from Cosmological N-body Simulations

Supermassive Black Hole Growth from Cosmological N-body Simulations. Miroslav Micic Kelly Holley-Bockelmann Steinn Sigurdsson Tom Abel. Want more info? See astro-ph/0703540. Original goal: approach SMBH merger rates ‘from the opposite direction’ of EPS. •. •.

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Supermassive Black Hole Growth from Cosmological N-body Simulations

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  1. Supermassive Black Hole Growth from Cosmological N-body Simulations Miroslav Micic Kelly Holley-Bockelmann Steinn Sigurdsson Tom Abel Want more info? See astro-ph/0703540

  2. Original goal: approach SMBH merger rates ‘from the opposite direction’ of EPS • • • EPS-derived BH merger rates (per year) • 0.1 – 100 Haehnelt 94 • 1 - 100 Menou et al 01 • 10 Sesana et al 04 • 15 - 350 Wyithe + Loeb 03 • 15 Rhook + Wyithe 05 • •

  3. How binary black holes meet and merge Galaxy merger BHs bound O(106) pc O(10) pc O(10-5) pc Dynamical friction 3-body scattering Gravitational radiation O(108) yr > O(1010) yr!** > O(1010) yr!* **in a static spherical galaxy with permanent ejections and no resonances *not anymore…thanks to excision and AMR

  4. 10 Mpc3 from z=40-0 with 2 Mpc refined sphere Mlow = 5.6 x 107 M rlow=4 kpc N=2 x 106 Mhigh = 8.9 x 105 M rhigh=2 kpc N=5 x 106 The nuts and bolts:

  5. Zooming into a group-sized volume of the universe Micic, HB, and Sigurdsson matter = 0.3baryon= 0.045 dark energy = 0.7 n=1 8 = 0.9 h=0.7

  6. Strategy: Pop III seeds and fast, efficient mergers • identify all the halos at z=20, and seed those with M > few 107 M with 200 M BHs • continue seeding new halos until z~12 (Pop III star formation squelched by UV background…) • Trace the evolution of halos and their embedded BHs from z = 20-0. • Assume that BHs merge once the halos merge. • Explore three accretion schemes: • Dry mergers only • Salpeter accretion excited by at least 4:1 mergers. • Salpeter accretion excited by M1:M2 < 10:1 mergers.

  7. M 31 Sgr A*

  8. High mass ratio ~ 1000 M mergers dominate 2<z<6  ULXs? Max black hole merger rate is ~ 55 per year Low mass ratio, ~ 1000 M BH mergers most abundant overall

  9. Intermediate and Supermassive BH Growth • BH merger rates ~55 per year • Forming a 106 M SMBH requires major merger gas accretion • To form a 107 M SMBH must also enlist gas accretion during minor mergers • Largest SMBH is in place by z= 6, thereafter growth by mergers only (AGN era  LISA era?) • Lots of rogue IMBHs in a Milky Way-sized halo!

  10. A gravitational wave implication Next paper: Can LISA be used as a tool to constrain BH growth mechanisms? • ‘new’ IMBH-SMBH merger source with rates > O(10) per year

  11. …and a surprise: BH mass a product of environment • a few isolated halos have extremely underweight bhs

  12. Following the leads with better dynamics Suppression mechanisms • gravitational wave kicks! • proper treatment of dynamical friction Cosmic variance -- several realizations of same volume (~105 CPU hrs) How robust is this merger rate? Smooth accretion – tidal disruption + capture and inspiral Do those BHs in the isolated halos stay vastly underweight? How does this relate to downsizing? Explore rogue black hole dynamics within Milky Way halo Smaller volume, better resolved simulation – 1 pc resolution with on the fly BH mergers

  13. Spitballing: Is there a variable spread in M-sigma? Largest SMBHs require ‘all’ accretion mechanisms + kicks inefficient (early growth) IMBHs have many formation/growth channels+ kicks efficient Ho et al 2003

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