Mitch Begelman JILA, University of Colorado GROWING BLACK HOLES

COLLABORATORS Marta Volonteri (Michigan) Martin Rees (Cambridge) Elena Rossi (JILA/Leiden) Phil Armitage (JILA) Isaac Shlosman (JILA/Kentucky) Kris Beckwith (JILA) Jake Simon (JILA)

EARLY QSOs with M>10 9 M  at z>6 OFTEN One per present-day galaxy BLACK HOLES FORMED…

HOW DID THESE BLACK HOLES GET THEIR START?

2 SCHOOLS OF THOUGHT: Pop III remnants –Stars form, evolve and collapse –M * ~10 3 M  –M BH ~10 2 M  Direct collapse –Massive gas cloud accumulates in nucleus –Supermassive star forms but never fully relaxes; keeps growing until collapse –M * >10 6 M  –M BH >10 4 M 

Rees, Physica Scripta, 1978 Rees’s flow chart

32 years later … Begelman & Rees, “Gravity’s Fatal Attraction” 2 nd Edition, 2010

Begelman & Rees, “Gravity’s Fatal Attraction” 3 nd Edition E-book? Keeping up with the times…

Pop III remnants –~100 (?) M  BHs form at z > 20 – M  halos, T vir ~ K –Grow by mergers & accretion –Problems: Slingshot ejection from merged minihalos? Feedback/environment inhibits accretion? Direct collapse –Initial BH mass = ? at z < 12 – M  halos, T vir >10 4 K –Grow mainly by accretion –Problem: Fragmentation of infalling gas? Smaller seeds, more growth time Larger seeds, less growth time TRADEOFFS:

STAGE I: COLLECTING THE GAS The problem: angular momentum The solution: self-gravitating collapse

SELF-GRAVITATING COLLAPSE: A GENERIC MECHANISM: “Normal” star formation Pop III remnants Direct collapse

DM gas DM gas Halo with slight rotation Gas collapses if “BARS WITHIN BARS” Shlosman, Frank & Begelman 1989 Dynamical loss of angular momentum through nested global gravitational instabilities

Wise, Turk, & Abel 2008 Collapsing gas in a pre-galactic halo: R -2 density profile

Wise, Turk, & Abel 2008 Global instability, “Bars within Bars”: Instability at distinct scales → nested bars

WHY DOESN’T THE COLLAPSING GAS FRAGMENT INTO STARS? IT’S COLD ENOUGH … … BUT IT’S ALSO HIGHLY TURBULENT

Wise, Turk, & Abel 2008 Collapse generates supersonic turbulence, which inhibits fragmentation:

HOW TURBULENCE COULD SUPPRESS FRAGMENTATION Begelman & Shlosman 2009 Razor-thin disk (Toomre approximation): FRAGMENTATION SETS IN BEFORE BAR INSTABILITY ROTATIONAL SUPPORT ⇨ ⇦ FRAGMENT SIZE THE KEY IS DISK THICKENING BAR FRAGMENTS

HOW TURBULENCE COULD SUPPRESS FRAGMENTATION Begelman & Shlosman 2009 Disk thickened by turbulent pressure: BAR INSTABILITY SETS IN BEFORE FRAGMENTATION ROTATIONAL SUPPORT ⇨ ⇦ FRAGMENT SIZE THE KEY IS DISK THICKENING BAR FRAGMENTS WHY? THICKER DISK HAS “SOFTER” SELF-GRAVITY ⇨ LESS TENDENCY TO FRAGMENT (DOESN’T AFFECT BAR FORMATION)

HOW TURBULENCE COULD SUPPRESS FRAGMENTATION Begelman & Shlosman % of turbulent pressure used for thickening : ENOUGH TO KILL OFF FRAGMENTATION ROTATIONAL SUPPORT ⇨ ⇦ FRAGMENT SIZE THE EFFECT IS DRAMATIC BAR FRAGMENTS MORE SIMULATIONS (WITH HIGHER RESOLUTION) NEEDED!

At radiation trapped in infalling gas halts the collapse Rapid infall can’t create a black hole directly…

STAGE II: SUPERMASSIVE STAR

SUPERMASSIVE STARS Proposed as energy source for RGs, QSOs Burn H for ~10 6 yr Supported by radiation pressure fragile Small P g stabilizes against GR to 10 6 M  Small rotation stabilizes to M  Hoyle & Fowler 1963

THINGS HOYLE & FOWLER DIDN’T KNOW ABOUT SUPERMASSIVE STARS They are not thermally relaxed … because they didn’t worry about how they formed

INCOMPLETE THERMAL RELAXATION SWELLS THE STAR:

THINGS HOYLE & FOWLER DIDN’T KNOW ABOUT SUPERMASSIVE STARS They are not thermally relaxed They are not fully convective … because they didn’t worry about how they formed

STRUCTURE OF A SUPERMASSIVE STAR CONVECTIVE CORE matched to RADIATIVE ENVELOPE Scaled radius POLYTROPE “HYLOTROPE” Thanks, G. Lodato & A. Accardi! (hyle, “matter” + tropos, “turn”)

HYLOTROPE, NOT HELIOTROPE!!

FULLY CONVECTIVE PARTLY CONVECTIVE MAX. MASS INCOMPLETE CONVECTION DECREASES ITS LIFE & MAX. MASS

THINGS HOYLE & FOWLER DIDN’T KNOW ABOUT SUPERMASSIVE STARS They are not thermally relaxed They are not fully convective If made out of pure Pop III material they quickly create enough C to trigger CNO … because they didn’t worry about how they formed

METAL-POOR STARS BURN HOTTER

A BLACK HOLE FORMS SMALL (< 10 3 M  ) AT FIRST … … BUT SOON TO GROW RAPIDLY

STAGE III: QUASISTAR

“QUASISTAR” Black hole accretes from envelope, releasing energy Envelope absorbs energy and expands Accretion rate decreases until energy output = Eddington limit – supports the “star” Begelman, Rossi & Armitage 2008

SO THE BLACK HOLE GROWS AT THE EDDINGTON LIMIT, RIGHT?

BUT WHOSE LIMIT? EDDINGTON

GROWTH AT EDDINGTON LIMIT FOR ENVELOPE MASS > X BH MASS EXTREMELY RAPID GROWTH

“QUASISTAR” Resembles a red giant Radiation-supported convective envelope Photospheric temperature drops as black hole grows Central temp. ~10 6 K Radius ~ 100 AU T phot drops as BH grows

DEMISE OF A QUASISTAR Critical ratio: R M =(Envelope mass)/(BH mass) R M < 10: “opacity crisis” (Hayashi track) R M < 100: powerful winds, difficulty matching accretion to envelope (details very uncertain) Final black hole mass:

STAGE IV: “BARE” BLACK HOLE “Normal” growth via accretion & mergers

THE COSMIC CONTEXT Collapse occurs only in gas-rich & low ang. mom. halos Need ang. mom. parameterλ~ vs. meanλ~ Competition with Pop III seeds Pre-existing Pop III remnants may inhibit quasistar formation... but pre-existing quasistars can swallow Pop III remnants Merger-tree models vs. observational constraints: Number density of BHs vs. z (active vs. inactive) Mass density of BHs vs. z (active vs. inactive) BH mass function vs. z Total AGN light (Soltan constraint) Reionization Volonteri & Begelman 2010

BLACK HOLE mass density All BHs: (thin lines) Active BHs: (thick lines) TOTAL AGN LIGHT POP III ONLY Volonteri & Begelman 2010

CAN SUPERMASSIVE STARS OR QUASISTARS BE DETECTED? Quasistars peak in optical/IR: some hope? Supermassive stars: …strong UV source (hard to distinguish from clusters of hot stars)

JWST quasistar counts T phot =4000 K Band: 2-10  m Sens. 10 nJy Lifetime ~10 6 yr λ spin <0.02 λ spin <0.01 1/JWST field

WHAT ABOUT M-σ? Do AGN outflows really clear out entire galaxies? – or is global feedback a “red herring”? Do BH grow mainly as Eddington-limited AGN or in smothered, “force-fed” states (e.g., following mergers) if the latter, then BH growth could be coupled to σthrough infall rate σ 3 /G... but what is the regulation mechanism?

To conclude … BOTH ROUTES TO SUPERMASSIVE BLACK HOLE FORMATION ARE STILL IN PLAY MASSIVE BLACK HOLE FORMATION BY DIRECT COLLAPSE LOOKS PROMISING THE PROCESS INVOLVES 2 NEW CLASSES OF OBJECTS QUASISTARS AT Z~6-10 MIGHT BE DETECTABLE WITH JWST Requires self-gravitating infall without excessive fragmentation Supermassive stars ⇨ initial seeds Quasistars ⇨ rapid growth in massive cocoon Many unsolved problems: Effects of mass loss? Late formation after mergers? Formation around existing black holes?....

DIRECT COLLAPSE LOOKS PROMISING CORE COLLAPSE OF SUPERMASSIVE STARS QUASISTARS DETECTABLE? RAPID GROWTH INSIDE MASSIVE COCOONS