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The main growth modes of disks, bulges, and central black holes: Mergers - Violent Instabilities - Secular Evolution Frédéric Bournaud - CEA Saclay with.

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Presentation on theme: "The main growth modes of disks, bulges, and central black holes: Mergers - Violent Instabilities - Secular Evolution Frédéric Bournaud - CEA Saclay with."— Presentation transcript:

1 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

2 The main growth modes of disks, bulges, and central black holes: Mergers - Violent Instabilities - Secular Evolution Violent Disk Instability = V.D.I. (© Avishai Dekel) Gas rich rotating disks wildly unstable with giant clumps, asymetries, rings, etc: - frequently observed at z>1, - predicted from cold flow accretion (Cowie, Elmegreen, Genzel, Agertz, Ceverino…)

3 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 rot n curves (initially) Martig Bournaud Dekel Teyssier Croton 2010, Zoom-in simulations from a DM-only run 33 field / loose group galaxies 1 x < M star (z=0) < 2 x SF, feedback, resolution 130pc

4 Spiral galaxies dont require calm histories Martig et al. 2010, 2012 V.D.I. Major mergers Early spheroid All have final bulge fractions of Late accretion, feedback, stellar mass-loss make disk-dominated gals.

5 Spiral galaxies dont require calm histories Martig et al. 2010, 2012 V.D.I. Major mergers Early spheroid No feedback Feedback and stellar mass loss See also Leitner & Kravtsov 2010 Late accretion, feedback, stellar mass-loss make disk-dominated gals.

6 No correlation between z~2 and z=0 properties - Many disk-dominated galaxies (today) are spheroid-dominated at z=2 - Final morphology starts being established at z~ Martig et al. 2012

7 The early phases: violent assembly (mergers + V.D.I.) End-products of high-z mergers + VDI : halo, bulge, thick disk Martig et al Bournaud Elmegreen & Martig 09 Violent phase VDI+mergers Secular growth Vertical profile

8 The late phase: secular growth (z<1) Products: thin disk and late bulge growth Smooth infall 1-10 M O /yr There are still significant mergers Bulge grows by ~20% (bars+mergers) Modern thin disk grows by a few M O - Bournaud & Combes 2002s 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 the formation of modern disks Kraljic Bournaud et al. in prep Early transient bars Long-lived secular bars zbar~0.7 Secular phase … VDI+mergers

9 Massive disks stabilize earlier Rapid mass infall stops earlier in massive systems Late growth occurs mostly in low-mass spirals V.D.I. ends-up earlier in more massive galaxies (see also Marcello Cacciatos 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 High mass Low mass

10 At least three main modes of galaxy evolution How do they impact Star Formation? Black hole growth? Mergers V.D.I. Secular NGC 520 fast slow Externally-drivenSmooth infall + internal physics

11 Resolving star formation in secular disks Bournaud Elmegreen Teyssier Moderate density gas Dense gas clouds and sub-clouds at n > 10 5 cm -3 Star formation explicitely resolved sub-resolution scheme: fixed SFE in HCN cores hydro resolution of 100pc => T>10 4 K => Mach<1 in a 2D disk hydro resolution of 10pc => T 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…

12 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

13 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

14 Resolving star formation in secular disks H2-driven SF HI-dominated break 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

15 ISM and SF in mergers: a different mode? Teyssier Chapon & Bournaud 2010 Bournaud Duc & Emsellem 2008 Powell et al Gas velocity dispersion increases x4, x5… Not just from feedback after the starburst, also in early pre-burst mergers During Myr, non-equilibrium turbulence, excess of high-density gas

16 Dense gas excess in mergers Gao & Solomon 2004 Juneau et al Garcia Burillo et al Model consistent with the high HCN/CO ratios seen in ULIRGs During Myr, non-equilibrium turbulence, excess of high-density gas ISM and SF in mergers: a different mode?

17 Daddi+2010 Two regimes, but apparent bimodality only if we select the most actively starbursting mergers (as in observations) Teyssier Chapon & Bournaud 2010 Bournaud Duc & Emsellem 2008 Powell et al ISM and SF in mergers: a different mode?

18 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-z gas-rich turbulent disks Full feedback: SN, HII photoionisation, Radiation pressure

19 SF in high-z disks: how different is it? High-z disks High-z mergers Two regimes, but apparent bimodality only if we select the most actively starbursting mergers (as in observations) Daddi+2010 Renaud + in prep

20 But when does the black hole grow ? Mergers V.D.I. Secular NGC 520 fast slow Externally-drivenSmooth infall + internal physics Efficient trigger but dont dominate high-z X-ray AGN (Grogin+05, Gabor+09, Kocevski+11) Only LL-AGNs, minor contribution to BH growth (Hopkins & Hernquist 07) ??

21 Instability-driven inflows in turbulent disks energy dissipation (through turbulence) = strong gravitational torquing = mass inflow in a dynamical time, down to the central pc Bournaud Dekel Teyssier Cacciato Daddi Juneau Shankar 2011 (see also Marcello Cacciatos talk)

22 Instability-driven inflows in turbulent disks Bournaud Dekel ~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

23 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, [O III ] selected, redshift and mass-matched, M*~ few 10 10

24 How can we find obscured AGN? Juneau Dickinson Alexander & Salim Empirical dividing Lines (from >100,000 SDSS galaxies at 0.05

25 High AGN fraction in Clumpy Disks Bournaud Juneau Clumpy disks have high [O III ] excitation - P AGN much higher in clumpy disks - Confirmed with X-ray stacking - Intrinsic L X is a few erg/s (obscured but significant BH accretion rate)

26 The balance is still unknown… Mergers V.D.I. Secular NGC 520 fast slow Externally-drivenSmooth infall + internal physics SF differs AGN feeding differs But even the violent modes contribute to the formation of MW-like spirals


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