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)
Spirals
Elliptical
Color
Blue
Red
Mass
Small-medium
Small-huge
Age
Young
Old
Gas
Lots
Little

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. When can gas be hydrostatic? (argument for the adiabatic case)
Ideal gas:
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. Let’s check the stability behind the shock
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:

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. Cold Flows in Halos at z>1 most halos are M<Mshock→ cold flows
1013
1012
1011
M* of Press Schechter
shock heating
Mvir [Mʘ]
2σ (4.7%)
Assuming:
Overdensity evolution
Metalicity
evolution
at z>1 most halos are M<Mshock→ cold flows
1σ (22%)
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
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
1012Mʘ
1013Mʘ Mh

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 galaxies Cold accretion vs. Merger induced star bursts
BX/BM/sBzK,
Dekel, Birnboim et al. 2009,
Nature

32. z=2 disks SINS 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= M⊙,
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. The galaxy bi-modality High-z star forming galaxies
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
Allen & Ebeling
No cool (<1keV) gas
Star formation in brightest central galaxy lower by than expected from cooling
BCG smaller by a factor or a few than expected (“failure to thrive”)

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
Other forms of gravitational heating: conduction, feeding by streams that break near the center
Dekel & Birnboim 2008

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

42. Clump physics Hydrodynamic drag Jeans mass (Bonnor-Ebert)
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: M⊙ (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