The main growth modes of disks,

bulges, and central black holes:

Mergers - Violent Instabilities - Secular Evolution

Frédéric Bournaud - CEA Saclay

with

Stéphanie Juneau, Marie Martig, Florent Renaud, Jared Gabor,

Katarina Kraljic, Leila Powell,

Romain Teyssier, Emeric Le Floch’, Emanuele Daddi, David

Elbaz…

and

Avishai Dekel

The main growth modes of disks,

bulges, and central black holes:

Mergers - Violent Instabilities - Secular Evolution

Violent Disk Instability = V.D.I. (© Avishai Dekel)Violent Disk Instability = V.D.I. (© Avishai Dekel)

Gas rich rotating diskswildly unstable with giant clumps,asymetries, rings, etc:

- frequently observed at z>1,

- predicted from cold flow accretion

(Cowie, Elmegreen, Genzel, Agertz, Ceverino…)

A sample of 33 spirals in -CDM

-The main ‘seed’ galaxy at z=5 and each incoming companion

at the virial radius are « idealized » :

Core DM halo with Burkert profile imposed by hand

=> -CDM merger/accretion history

with realistic halo profiles and rotn curves (initially)

Martig Bournaud Dekel Teyssier Croton 2010, 2012

- Zoom-in simulations from a DM-only run

33 field / loose group galaxies

1x1010 < Mstar(z=0) < 2x1011

- SF, feedback, resolution 130pc

Spiral galaxies don’t require calm historiesMartig et al. 2010, 2012

V.D.I.V.D.I.

Major mergersMajor mergers

Early spheroidEarly spheroid

All have final bulge fractionsof 0.1-0.3

Late accretion, feedback, stellar mass-loss make disk-dominated gals.

Spiral galaxies don’t require calm histories

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Martig et al. 2010, 2012

V.D.I.V.D.I.

Major mergersMajor mergers

Early spheroidEarly spheroid

No feedback

Feedback and stellar mass loss

See also Leitner & Kravtsov 2010

Late accretion, feedback, stellar mass-loss make disk-dominated gals.

No correlation between z~2 and z=0 properties

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- Many disk-dominated galaxies (today) are spheroid-dominated at z=2

- Final morphology starts being established at z~0.7-1.0

Martig et al. 2012

The early phases: violent assembly (mergers + V.D.I.)

End-products of high-z mergers + VDI : halo, bulge, thick disk

Martig et al. 2012Bournaud Elmegreen & Martig 09

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Violent phaseVDI+mergers

Secular growth

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Vertical profile

The late phase: secular growth (z<1)

Products: thin disk and late bulge growth

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Smooth infall 1-10 MO/yr

There are still significant mergers

Bulge grows by ~20% (bars+mergers)

Modern thin disk grows by a few 1010 MO

- Bournaud & Combes 2002’s theory of cyclic bars is partly right (but only partly)

- Models agree with data (limited to z=0.8)(Abraham+99, Elmegreen+04, Jogee+07, Sheth+08)

- The raising bar fraction traces theformation of modern disks

Kraljic Bournaud et al. in prep

Early

tran

sien

t ba

rs

Long

-live

d

secu

lar b

ars

zbar

~0.7

Secular phase … VDI+mergers

Massive disks stabilize earlier

Rapid mass infall stops earlier in massive systems

Late growth occursmostly in low-mass spirals

V.D.I. ends-up earlier in moremassive galaxies (see also Marcello Cacciato’s talk)

« Downsizing of bar formation »

- traces downsizing of (thin) disk formation

- observed (Sheth+08)

- origin: later accretion and later VDI in lower-mass galaxies

Kraljic Bournaud et al. in prep

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High massLow mass

At least three main modes of galaxy evolution

How do they impact Star Formation? Black hole growth?

MergersV.D.I.

Secular

NGC 520

fast

slow

Externally-driven Smooth infall + internal physics

Resolving star formation in secular disksBournaud Elmegreen Teyssier + 2010

Moderate density gas

Dense gas clouds

and sub-clouds at n > 105cm-3

Star formation

explicitely resolved

sub-resolution scheme:fixed SFE in ‘‘HCN’’ cores

hydro resolution of 100pc => T>104K => Mach<1 in a 2D disk

hydro resolution of 10pc => T<103K => Mach>1 but still a 2D disk

hydro resolution of 1pc => supersonic 3D turbulence

Here a disk at 0.8pc, AMR,cooling curve down to ~100K, with stellar dynamics, SF, feedback..

We now resolve where SF clouds are, how dense they are, their main substructures, etc…

The ISM turbulence cascade resolved

- The same power spectrum is observed in disk galaxies

(Elmegreen+93, Dutta+2010,11, Block+2010)

- Energy injection at the Jeans length, through gravitationnal instabilites

- Regulation by stellar feedback required for a steady state distribution

> 80% of the gas mass in a trans-sonic or supersonic regime

Bournaud Elmegreen Teyssier + 2010

The ISM turbulence cascade resolved

- Self-regulated turbulence => log-normal density PDF

- Local SF rate: constant efficiency per free-fall time

- The global SFR follows realistic scaling relations

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Resolving star formation in secular disks

H2-driven SF

HI-dominatedbreak

Leroy, Bigiel et al.

- Self-regulated turbulence => log-normal density PDF

- Local SF rate: constant efficiency per free-fall time

- The global SFR follows realistic scaling relations

ISM and SF in mergers: a different mode?

Teyssier Chapon & Bournaud 2010Bournaud Duc & Emsellem 2008Powell et al. 2012

Gas velocity dispersion increasesx4, x5…

Not just from feedback after the starburst, also in early pre-burst mergers

During 100-200Myr, non-equilibrium turbulence, excess of high-density gas

Dense gas excess in mergers Gao & Solomon 2004 Juneau et al. 2009 Garcia Burillo et al. 2011

Model consistent with the highHCN/CO ratios seen in ULIRGs

During 100-200Myr, non-equilibrium turbulence, excess of high-density gas

ISM and SF in mergers: a different mode?

Daddi+2010

Two regimes, but apparent bimodality only if we selectthe most actively starbursting mergers (as in observations)

Teyssier Chapon & Bournaud 2010Bournaud Duc & Emsellem 2008Powell et al. 2012

ISM and SF in mergers: a different mode?

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SF in high-z disks: how different is it?

- High gas fraction ~50%

- Self-regulation at Q=1 implies higher turbulent speed >50km/s (observed)

- High Jeans mass/length => giant clumps

- But same self-regulated turbulence, log-normal PDF and star-forming part..

Renaud + in prep

New models of high-zgas-rich turbulent disks

Full feedback: SN, HII photoionisation,Radiation pressure

SF in high-z disks: how different is it?

High-z disks

High-z mergers

Two regimes, but apparent bimodality only if we selectthe most actively starbursting mergers (as in observations)

Daddi+2010

Renaud + in prep

But when does the black hole grow ?

MergersV.D.I.

Secular

NGC 520

fast

slow

Externally-driven Smooth infall + internal physics

Efficient trigger butdon’t dominate high-z X-ray AGN

(Grogin+05, Gabor+09,Kocevski+11)

Only LL-AGNs,minor contribution to BH growth

(Hopkins & Hernquist 07)

????

Instability-driven inflows in turbulent disks

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energy dissipation(through turbulence)

=strong gravitational

torquing=

mass inflow in a dynamicaltime, down to the central pc

Bournaud Dekel Teyssier Cacciato Daddi Juneau Shankar 2011

(see also Marcello Cacciato’s talk)

Instability-driven inflows in turbulent disks

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Bournaud Dekel + 2011

~1 Mo/yr flows to the central pc, available to the BH

But high gas column density in a thick disk=> X-ray AGN signal would in general be obscured

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VDI galaxies and secular disks at z~0.7

Very clumpy / VDI

Secular - arm/bar-dominated

Bournaud, Juneau, Le Floch’, Mullaney, Daddi, Dekel et al 2011

In GOODS-South, [OIII] selected, redshift and mass-matched, M*~ few 1010

How can we find obscured AGN?

Juneau Dickinson Alexander & Salim 2011

1- Empirical dividing Lines (from >100,000 SDSS galaxies at 0.05<z<0.1)

2- Probabilistic approach P(AGN) = probability of presence of AGN

MEx-AGN

MEx-SF

BPT-AGN

BPT-SFcomposite

BPT-

The Mass-excitation (MEx) diagnostic

High AGN fraction in Clumpy Disks

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Bournaud Juneau + 2011

- Clumpy disks have high [OIII] excitation

- PAGN much higher in clumpy disks

- Confirmed with X-ray stacking

- Intrinsic LX is a few 1042 erg/s

(obscured but significant BH accretion rate)

The balance is still unknown…

MergersV.D.I.

Secular

NGC 520

fast

slow

Externally-driven Smooth infall + internal physics

SF differs

AGN feedingdiffers

But even the violent modes contribute to the formation of MW-like spirals