Virial shocks in galaxy and cluster halos

1. Virial shocks in galaxy and cluster halos Yuval Birnboim Hebrew University of Jerusalem, Israel

2. What governs evolution of galaxies? M100 and NGC1365 (AAO) M87 (AAO)

3. Gas & Galaxies:Common wisdom Hubble expansion Gravitational instability Shock heating Cooling Angular momentum Accretion to galactic spiral disk Stars, SN, feedback

4. Galaxy/Cluster segregation Rees & Ostriker (1977) Silk (1977) Binney(1977) White & Rees (1978): tcool<tff – one central object (galaxy) tcool>tff – hydrostatic halo + many objects (cluster) Blumenthal, Faber, Primack & Rees 86

5. Evolution of radii of gas shells– big halo T(k) shocked gas cooling radius disk Birnboim & Dekel 2003

6. Same stuff for a smaller halo T(k) no shock – Cools like crazy! disk

7. Ideal gas: When can gas be hydrostatic?(argument for the adiabatic case) • Gas in the halo Isentropic: Power law profile: Homologeous collapse

8. Start with hydrostatic equilibrium: • The gravitational acceleration is: Stable: small perturbation inwards increases the ratio of pressure to gravity

9. the ideal EOS: Let’s check the stability behind the shock for non-adiabatic processes: Compression time Cooling time Birnboim & Dekel 2003

10. Perturbation analysis of the force equation (sub-sonic) (homology)

11. … and after some algebra: So,

12. Assume hypothetic shock there and find out. Had there been a shock here… Would’ve it been stable?

13. Simulation confirms analytic model: shock when eff > crit=1.43 No free parameters, no fudge factors

14. M* of Press Schechter Cold Flows in Halos 1013 1012 1011 shock heating Mvir[Mʘ] 2σ (4.7%) • Assuming: • Overdensity evolution • Metalicity • evolution at z>1 most halos are M<Mshock→cold flows 1σ (22%) 0 1 2 3 4 5 redshift z Dekel & Birnboim 06

15. Shock always forms at same mass Time(Gyr) Time(Gyr)

16. Cold flows and: • The galaxy bi-modality • High-z star forming galaxies • Groups and clusters

17. Applications - Cold flows and: • The galaxy bi-modality • High-z star forming galaxies • Groups and clusters

18. Bi-modality: Age vs Stellar Mass young old young old M*crit~3x1010Mʘ SDSS Kauffmann et al. 03

19. Transition Scale Bulge/Disk Surface Brightness HSB spheroids LSB disks M*crit~3x1010Mʘ M*crit~3x1010Mʘ SDSS Kauffmann et al. 03

20. Color-Magnitude bimodality & B/D depend on environment (ie. “halo mass”) environment density: low high very high Green valley disks spheroids Mhalo<6x1011 “field” Mhalo>6x1011 “cluster” SDSS: Hogg et al. 03

21. Halo gas and AGN feedback Feedback “strength” Hot halo 1011Mʘ Mh 1012Mʘ 1013Mʘ

22. Halo gas and AGN feedback Somerville et al. 2008

23. Hot halos and Bi-modality • Green valley - a sharp cutoff in gas accretion to galaxies • Feedback processes are “too smooth” • Formation of hot halos makes feedback effects abrupt

24. Applications • The galaxy bi-modality • High-z star forming galaxies • Groups and clusters

25. Deviations from the spherical cow approximation

26. high-sigma halos: fed by relatively thin, dense filaments typical halos: reside in relatively thick filaments, fed spherically the millenium cosmological simulation

27. Cosmological Context MW: Halo is hot, filaments are hot. Groups, Clusters, satellites Larger than average Rhalo>>Dfilament Cold flows Always unstable (1D analysis) Dekel & Birnboim 2006

28. 3D SPH hydro-simulations Kereš et al. 2005 Kereš et al. 2009

29. 3D Eulerian hydro-simulations Ocvirk et al. 2008 2e12 halo, z=4 2e12 halo, z=2.5

30. Accretion at high-z Dekel & Birnboim 2006 Keres et al. 05-09 Agertz et al. 2009 Wechsler et al 2002, Dekel et al. 2009

31. Star forming galaxiesCold accretion vs. Merger induced star bursts BX/BM/sBzK, Dekel, Birnboim et al. 2009, Nature

32. z=2 disksSINS Hα survey Förster Schreiber et al. 2009 Daddi et al. 2004 Bouché et al. 2007

33. High accretion rate and galaxy structure: Clump clusters Clumps in clump clusters: M=107-109M⊙, D=~1kpc (Elmegreen et al. 07,09, SINS) Gas splashes into galaxies at ~200km/sec → Turbulence in ISM is ~50km/sec → Jeans mass goes up, disk becomes more Toomre stable Elmegreen et al. 2007

34. High accretion rate and galaxy structure: Clump clusters Genzel et al. 2010 Ceverino, Dekel & Bournaud 2009

35. Applications • The galaxy bi-modality • High-z star forming galaxies • Groups and clusters Towards a solution of the overcooling problem of clusters (the “high-risk—high-gain” part of the talk)

36. The cooling flow Problem in Cool Core Clusters • No cool (<1keV) gas • Star formation in brightest central galaxy lower by 10-100 than expected from cooling • BCG smaller by a factor or a few than expected (“failure to thrive”) Allen & Ebeling

37. Immediate suspect: AGNs Artist’s impression for supermassive black hole, NASA/JPL-Caltech M87 – HST image

38. Criteria for cluster heat source 1) Enough energy 2) Smooth in time (toff<tcool) 3) Smooth in space (<10kpc) 4) No explosions, please

39. Clusters are not smooth! Courtesy of Volker Springel

40. Accretion and Gravitational heating in Clusters Dekel & Birnboim 2008

41. Clump physics Heating by baryonic cold (10^4K) clumps • Hydrodynamic drag:

42. Clump physics Heating by baryonic cold (10^4K) clumps • Hydrodynamic drag • Jeans mass (Bonnor-Ebert) • K-H/R-T instabilities and clump fragmentation • DF • Conduction/evaporation (Gnat et al. 2010) Heating 1gr/cm^3 10-3gr/cm^3

43. Gravitational heating by clumps Murray & Lin 2004 Dekel & Birnboim 2008

44. 5% of baryons in clumps of 108M⊙Clumps + Convection Birnboim et al. 2011, submitted

45. Cold gas in Perseus HVCs Conselice et al. 2001 Mass of structures: 106-108M⊙(Fabian et al. 2008)

46. Summary • Threshold mass for hot halo formation ~ 1012M⊙ • Crucial to matches the color magnitude bi-modality • Most stars formed through cold flows • In clusters, cold accretion in clumps actually heats!

47. Thank you