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

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

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

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

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

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

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

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

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

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

… and after some algebra:

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

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

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%) 0 1 2 3 4 5 redshift z Dekel & Birnboim 06

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

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

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

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

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

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

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

Halo gas and AGN feedback Somerville et al. 2008

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

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

Deviations from the spherical cow approximation

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

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

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

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

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

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

z=2 disks SINS Hα survey Förster Schreiber et al. 2009 Daddi et al. 2004 Bouché et al. 2007

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

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

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)

The cooling flow Problem in Cool Core Clusters Allen & Ebeling 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”)

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

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

Clusters are not smooth! Courtesy of Volker Springel

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

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

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

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

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

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

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!

Thank you