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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
Mergers and Elliptical Galaxies

Feedback in Elliptical Galaxies

No

Minor

Avishai Dekel HU Jerusalem

Galaxy Mergers, STScI, October 2006

outline
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
from blue to red sequence by shutdown dekel birnboim 06
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

in a standard semi analytic simulation galics

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

with shutdown above 10 12 m
With Shutdown Above 1012 Mʘ

color u-r

magnitude Mr

standard
Standard

color u-r

magnitude Mr

slide8

With Shutdown Above 1012 Mʘ

color u-r

magnitude Mr

slide9

Bulge to disk ratio

Environment dependence via halo mass

slide10

Effect of shutdown

Cattaneo, Dekel, Faber

model: no shutdown

model: with shutdown

Downsizing in the epoch of star formation

observed Thomas et al. 05

downsizing due to shutdown

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

downsizing by shutdown at m halo 10 12

z=2

Mhalo>1012

z=1

Mhalo>1012

Mhalo>1012

z=0

central

small

small satellite

big

Downsizing by Shutdown at Mhalo>1012
requirements
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
agn feedback
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?
slide15

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

little bursts of sfr to z 1
Little bursts of SFR to z~1

Noeske et al. (DEEP2)

slide17

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

slide18

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

slide19

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?

slide20

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

less massive halo m 1 8x10 10

virial radius

coldinfall

Less Massive halo M=1.8x1010

Eulerian: Kravtsov et al.

SPH: Keres et al.

slide23

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

shock heating scale

Birnboim & Dekel 03; Dekel & Birnboim 06

Shock-Heating Scale

stable shock

Mvir [Mʘ]

6x1011 Mʘ

unstable shock

fraction of cold gas in halos eulerian simulations

shock heating

Fraction of cold gas in halos: Eulerian simulations

Birnboim, Dekel, Kravtsov, Zinger 2006

z=3

z=4

z=1

z=2

shock propagates outward once m m crit
Shock propagates outward once M>Mcrit

T °K

1011Mʘ

shocked

cold infall

“disc”

Spherical hydro simulationBirnboim & Dekel 03

slide27

- Gravitational accretion energy ~ AGN energy:

Maintenance of Shutdown by Clumpy Accretion

Birnboim & Dekel 2007

slide28

Growth of a Massive Galaxy

T °K

1012Mʘ

1011Mʘ

shock-heated gas

“disc”

Naab, Johansson, Efstathiou, Ostriker 06

Spherical hydro simulationBirnboim & Dekel 03

slide30

- 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
toy model
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
slide33

Global energy budget: gravity vs cooling

rdeposit=0 cusp=1/0 Z=0.03 fb=0.1 z=0

global energy budget gravity vs cooling
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

slide35

Better deposit the energy in the core

Tgas~106-8

Tclump ~104

drag

slide36

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

clump mass penetration
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

heating vs cooling in m halo 10 12
Heating vs Cooling in Mhalo~1012

heating

cooling

Need Mclump < 109

R/Rvir

slide39

Heating vs Cooling in Mhalo~1015

heating

cooling

Need Mclump < 109

R/Rvir

heating cooling in the core
Heating/Cooling in the core

Need 106 < Mclump < 109

Halo Mass

slide41

At hi-z, in massive halos: Cold streams in a hot medium

Mhalo~1012.5 z~3

Cattaneo, Khalatyan, Steinmetz 2007

slide42

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

cold dense filaments and clumps 50 riding on dark matter filaments and sub halos
Cold, dense filaments and clumps (50%)riding on dark-matter filaments and sub-halos

Birnboim, Zinger, Dekel, Kravtsov

cold streams in big galaxies at high z

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

slide45

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

dark matter inflow in a shell 1 3r vir

one thick filament

several thin filaments

Dark-matter inflow in a shell 1-3Rvir

Seleson & Dekel

density

temperature

radial velocity

M*

M>>M*

slide47

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

slide48

Halos below Mshock~1012: cold accretion

No drag. Cold accretion to center. Star formation in disk galaxies

Tgas~104-5

Taccretion~104

cold flows in typical halos

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

conclusions
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
projected velocity dispersion low

The low velocities are consistent with merger remnants including dark matter

Projected Velocity Dispersion: low!

dark matter

stars

new

Dekel et al. 2005, Nature

minor mergers produce stellar halos with more radial orbits and lower dispersion velocities
Minor mergers produce stellar halos with more radial orbits and lower dispersion velocities

1:10

1:3

1:1

stellar dispersion velocities in the outskirts of ellipticals are low
Stellar dispersion velocities in the outskirts of ellipticals are low!

N4697

dark matter

naked

No dark matter in ellipticals?

Mendez et al. 2001

Romanowsky et al. 2003

the spherical jeans equation

Projection

The Spherical Jeans Equation

tracer density profile

total mass profile

velocity dispersion

radial dispersion profile

anisotropy

circular, isotropic, radial

Get low σp by: low V0, high β, high α

or by a face-on view of a triaxial (or rotating) system

slide60

high

low

high

high

Elongated (radial) orbits

Wide (circular) orbits

Velocities along the line of sight

The effect is amplified if the tracers are centrally condesed

projected velocity dispersion low1

The low velocities are consistent with merger remnants including dark matter

Projected Velocity Dispersion: low!

dark matter

stars

new

Dekel et al. 2005, Nature

minor mergers produce stellar halos with more radial orbits and lower dispersion velocities1
Minor mergers produce stellar halos with more radial orbits and lower dispersion velocities

1:10

1:3

1:1

conclusions stellar halo and dark halo
Conclusions: Stellar Halo and Dark Halo

PN kinematics is consistent with standard DM halos.

Low velocity dispersion due to the radial orbits of the halo stars, being torn by tides during the first close passage.

Robust to dissipation, bulge, and time after the merger. It depends on the strength of tides, which are strongest in minor mergers.

Globular clusters may show higher velocity dispersion because of their shallower density profile and less radial orbits.

A large variance is expected due to the direction of view because the systems are triaxial.

tilted scaling relations by differential dissipative mergers

non-dissipative

R

dissipative, with gas-fraction declining with mass

M*

Tilted Scaling Relations by Differential Dissipative Mergers

Dekel & Cox 2006

tilted scaling relations by wet mergers

Structural changes in mergers

~big disks

Scaling relations

SN feedback

consistent with the simple model of disk formation in LCDM halos

Top-hat model

Gradient of gas fraction

consistent with observed gradient along the blue sequence

Tilted Scaling Relations by Wet Mergers

Dekel & Cox 2006

The E scaling relations, including the tilt of the Fundamental Plane and the decline of density with mass can be reproduced by differential dissipation in major mergers.

The predicted properties of the progenitors:

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