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Mergers and Elliptical Galaxies

Mergers and Elliptical Galaxies. Feedback in Elliptical Galaxies. No. Minor. Avishai Dekel HU Jerusalem. Galaxy Mergers, STScI, October 2006. Quenching in ellipticals at z<2 Major mergers? AGN feedback? Trigger quenching by virial shock heating Maintenance by clumpy accretion

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Mergers and Elliptical Galaxies

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  1. Mergers and Elliptical Galaxies Feedback in Elliptical Galaxies No Minor Avishai Dekel HU Jerusalem Galaxy Mergers, STScI, October 2006

  2. Quenching in ellipticals at z<2 Major mergers? AGN feedback? Trigger quenching by virial shock heating Maintenance by clumpy accretion Star formation by clumpy flows in massive disks at z>2 Ellipticals by multiple minor mergers Outline

  3. Shutdown above a critical halo mass does wonders

  4. From blue to red sequence by shutdownDekel & Birnboim 06 1014 1013 1012 1011 1010 109 cold hot in hot Mvir [Mʘ] Mshock all cold 0 1 2 3 4 5 redshift z

  5. z=0 excess of big blue no red sequence at z~1 data --- sam --- not red enough too few galaxies at z~3 star formation at low z In a standard Semi Analytic Simulation (GalICS) Cattaneo, Dekel, Devriendt, Guiderdoni, Blaizot 06 color color u-r magnitude Mr

  6. With Shutdown Above 1012 Mʘ color u-r magnitude Mr

  7. Standard color u-r magnitude Mr

  8. With Shutdown Above 1012 Mʘ color u-r magnitude Mr

  9. Bulge to disk ratio Environment dependence via halo mass

  10. Effect of shutdown Cattaneo, Dekel, Faber model: no shutdown model: with shutdown Downsizing in the epoch of star formation observed Thomas et al. 05

  11. z=2 z=1 z=1 z=3 in place by z~1 turn red after z~1 Downsizing due to Shutdown Cattaneo, Dekel, Faber 2006 brightintermediate faint . central central/satellites satellites z=0 z=1 green valley at z=1 color magnitude

  12. z=2 Mhalo>1012 z=1 Mhalo>1012 Mhalo>1012 z=0 central small small satellite big Downsizing by Shutdown at Mhalo>1012

  13. Requirements What is the shutdown mechanism? • - energy source • - coupling to gas in inner halo • threshold Mhalo~1012Mʘ (M*~1010.5Mʘ) • long-term maintenance - stop gas supply • active z=2 to z=0

  14. AGN Feedback? • Adequate energy source, but • Origin of threshold mass? • Why after z~2? • Spread of the BH energy across the halo gas? • QSO’s are short-lived. ...Weak-AGN self-regulated feedback? • Coupling to gas requires a hot medium – origin?

  15. Major mergers as the trigger for shutdown (via SFR bursts or QSO activation)? Incomplete gas exhaustion by SFR. Via QSOs? SFR at z~0-1 shows little bursts

  16. Little bursts of SFR to z~1 Noeske et al. (DEEP2)

  17. Major mergers as the trigger for shutdown (via SFR bursts or QSO activation)? Complete gas exhaustion in mergers? Perhaps via AGNs? SFR at z~0-1 shows little bursts Merger rate too low. Only <10% of galaxies are perturbed (Lotz et al.). Mergers detectable for ~300 Myr, so rate <0.3 per galaxy per Gyr. But transition rate from BS to RS is >1

  18. RS color transition SFR BS z=1.25 mass z=0.75 Transition from BS to RS Dekel, Neistein, Faber dry assembly stellar assembly At z~1, the merger rate is not enough to explain the transition rate from blue to red

  19. Major mergers as the trigger for shutdown (via SFR bursts or QSO activation)? Complete gas exhaustion in mergers? Perhaps via AGNs? SFR at z~0-1 shows little bursts (Noeske et al.) Merger rate too low. Only ~10% of galaxies are perturbed (Lotz et al.). Mergers detectable for ~300 Myr, so rate ~0.3 per galaxy per Gyr. But transition rate from BS to RS is >1 Only 7% of the Green-Valley galaxies are perturbed (Lotz) Origin of the sharp threshold mass? Maintenance mechanism? Preventing secondary disk?

  20. Trigger of quenching: virial shock heating Birnboim & Dekel 2003; Dekel & Birnboim 2006 Rees & Ostriker 1977; Silk 1977; Binney 1977; Blumenthal et al 1984 Natural critical halo mass at 1012Mʘ No shutdown at z>2 due to cold streams A hot-dilute medium allows the coupling of.anyfeedback source (e.g. AGN) to the gas

  21. Virial shock heating above a critical halo mass ~1012

  22. virial radius coldinfall Less Massive halo M=1.8x1010 Eulerian: Kravtsov et al. SPH: Keres et al.

  23. Shock-stability analysis (Birnboim & Dekel 03): post-shock pressure vs. gravitational collapse Gas through shock: heats to virial temperature compression on a dynamical timescale versus radiative cooling timescale

  24. Birnboim & Dekel 03; Dekel & Birnboim 06 Shock-Heating Scale stable shock Mvir [Mʘ] 6x1011 Mʘ unstable shock

  25. shock heating Fraction of cold gas in halos: Eulerian simulations Birnboim, Dekel, Kravtsov, Zinger 2006 z=3 z=4 z=1 z=2

  26. Shock propagates outward once M>Mcrit T °K 1011Mʘ shocked cold infall “disc” Spherical hydro simulationBirnboim & Dekel 03

  27. - Gravitational accretion energy ~ AGN energy: Maintenance of Shutdown by Clumpy Accretion Birnboim & Dekel 2007

  28. Growth of a Massive Galaxy T °K 1012Mʘ 1011Mʘ shock-heated gas “disc” Naab, Johansson, Efstathiou, Ostriker 06 Spherical hydro simulationBirnboim & Dekel 03

  29. Clumpy cold accretion into a hot halo medium Springel

  30. - Gravitational accretion energy ~ AGN energy: Maintenance of Shutdown by Clumpy Accretion Birnboim & Dekel • - Accretion rate > cooling rate for M>1012Mʘ • Clumpy cold accretion into a hot medium - heating by ...drag, shocks and collisions. • 106-9 clumps penetrate to center, fragment and heat the ...gas everywhere

  31. Global energy budget: gravity vs cooling Tgas~106-8

  32. Toy Model Hydrostatic Equilibrium • Cooling: • Hot gas in hydrostatic equilibrium ...inside an NFW dark halo, fb~0.1. • Gas core or cusp • Radiative cooling, Z ρdm T core ρgas entropy • Heating: • - Cosmological accretion rate (Wechsler.et al), Vvir • Clumps (50%) fall to the core of a dark-matter potential well

  33. Global energy budget: gravity vs cooling rdeposit=0 cusp=1/0 Z=0.03 fb=0.1 z=0

  34. Global energy budget: gravity vs cooling z=2, DM cusp, fb=0.05 z=0, gas core, fb=0.1, Z=0.03 gas cusp, Z=0.1 Cannot overcome cooling if gas density is cuspy, r-2 Heating more efficient at z~2. Cusp puffs up. Easier maintenance later Gain more potential energy if brings mass to core

  35. Better deposit the energy in the core Tgas~106-8 Tclump ~104 drag

  36. Heating by Drag: Cold Clouds in a Hot Medium Toy simulations: Birnboim & Dekel Cosmological accretion rate at Vvir (Whechsler et al) 50% clumpy at ~Jeans mass: Mclump~108 in ~109 halos Tclump~104 (photo-ionized), pressure confined by hot medium Shocks/ram pressure: clumps share their gravitational energy with the hot medium, preferentially in the inner halo. Drag more efficient for less massive clumps. Tgas~106-8 Tclump ~104

  37. Clump mass: penetration Rule of thumb: clump pushes gas mass equivalent to itself before it is stopped and destroyed Small clumps: drag too strong - cannot penetrate to the inner halo Massive clumps: drag inefficient Clump Mass

  38. Heating vs Cooling in Mhalo~1012 heating cooling Need Mclump < 109 R/Rvir

  39. Heating vs Cooling in Mhalo~1015 heating cooling Need Mclump < 109 R/Rvir

  40. Heating/Cooling in the core Need 106 < Mclump < 109 Halo Mass

  41. At hi-z, in massive halos: Cold streams in a hot medium Mhalo~1012.5 z~3 Cattaneo, Khalatyan, Steinmetz 2007

  42. shock no shock Hi z, Massive Halos: Cold Streams in a Hot Medium in M>Mshock Totally hot at z<1 Cold streams at z>2 cooling

  43. Cold, dense filaments and clumps (50%)riding on dark-matter filaments and sub-halos Birnboim, Zinger, Dekel, Kravtsov

  44. cold filaments in hot medium Mshock~M* Mshock>>M* M* Cold Streams in Big Galaxies at High z 1014 1013 1012 1011 1010 109 all hot Mvir [Mʘ] Mshock all cold 0 1 2 3 4 5 redshift z

  45. high-sigma halos: fed by relatively thin, dense filaments → cold flows typical halos: reside in relatively thick filaments, fed ~spherically → no cold flows the millenium cosmological simulation

  46. one thick filament several thin filaments Dark-matter inflow in a shell 1-3Rvir Seleson & Dekel density temperature radial velocity M* M>>M*

  47. At z>2, halos>1012: cold clumpy streams No drag within stream. Cold clumps penetrate to center. Efficient star formation in massive disks Tgas~106-8 Tstream~104-5

  48. Halos below Mshock~1012: cold accretion No drag. Cold accretion to center. Star formation in disk galaxies Tgas~104-5 Taccretion~104

  49. 1013 1012 1011 M* of Press Schechter 0 1 2 3 4 5 Cold Flows in Typical Halos shock heating Mvir [Mʘ] 2σ (4.7%) at z>1 most halos are M<Mshock→cold flows 1σ (22%) redshift z

  50. Conclusions - Quenching triggered by virial shock heating in Mhalo>1012Mʘ • Maintenance by gravitational energy of accretion. Energy transferred to inner halo once medium is hot. heating > cooling for Mhalo>1012-13 - Heating by drag/shocks of cold clumps penetrating through hot medium to halo core. 106<Mclump<109. Shutdown for Mhalo>1012. Need hi-res simulations! • - Star formation by clumpy cold flows • - at z<2 in Mhalo<1012, in the absence of hot medium • - at z>2 in all halos, cold streams in hot medium • - Multiple minor mergers also • - produce stellar halos with low dispersion velocities • - can produce non-rotating, boxy, massive ellipticals

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