Bi-modality and Downsizing

Avishai Dekel HU Jerusalem

Bernard’s Cosmic Stories, Valencia, June 2006

Origin of E vs S Galaxies

A third type of Bernard’s students:A third type of Bernard’s students:

Those who were inspired by Jones’ 1976 reviewThose who were inspired by Jones’ 1976 review

SummaryQ: z<2: Bright, red & dead, E’s. No big blues. ………….Bi-modality, environment dependenceA: Shutdown in Mhalo>1012

Q: z~2-4: Massive, high-SFR disks(?)A: Cold flows (+mergers) even in Mhalo~1012

Trigger: virial shock heating (threshold mass) … …..Maintenance: “AGN feedback” (?)

Q: From the blue to the red sequence

A2: Feedback in Mhalo<1012 & the shutdown in Mhalo >1012

A: Two tracks: early/late shutdown, wet/dry mergers

A1: Not anti-hierarchical for DM halos !Q: Downsizing?

Birnboim & Dekel 03Dekel & Birnboim 06

Cattaneo, Dekel et al. 06

Neistein, van den Bosch & Dekel 06

Cattaneo, Dekel, Faber 06

Dekel et al. 05; Dekel & Cox 06

Seleson & Dekel 06

Bi-modality in color, SFR, bulge/disk

Disks and IrregularsDisks and Irregulars

E/S0/SaE/S0/Sa0.65<z<0.750.65<z<0.75

Bell

M*crit~3x1010Mʘ

Color-Magnitude bimodality & B/D depend on environment ~ halo

mass

SDSS: Hogg et al. 03

spheroids

disks

environment density: low high very high

Mhalo>6x1011 “cluster”

Mhalo<6x1011 “field”

Downsizing

Disks and IrregularsDisks and Irregulars

E/S0/SaE/S0/Sa0.65<z<0.750.65<z<0.75

Bell

z~3

z~1z<1

z~1

Standard Picture of Infall to a Disk

Perturbed expansionHalo virialization

Gas infall, shock heating at the virial radiusRadiative cooling Accretion to disc if tcool<tff

Stars & feedback

Rees & Ostriker 77, Silk 77, White & Rees 78, …

M<Mcool ~1012-

13M⊙

Growth of a Massive Galaxy

T °K

“disc”

shock-heated gas

1011Mʘ1012Mʘ

Spherical hydro simulation Birnboim & Dekel 03

A Less Massive Galaxy

“disc”

shockedcold infall

T °K

Spherical hydro simulation Birnboim & Dekel 03

1011Mʘ

z=4M=3x1011

Tvir=1.2x106

Rvir=34 kpc

Hydro Simulation: ~Massive M=3x1011

Kravtsov et al.

virial shock

virial shock

Kravtsov et al.

z=9M=1.8x1010

Tvir=3.5x105

Rvir=7 kpc

Less Massive M=1.8x1010

cold infall

virial radiu

s

Mass Distribution of Halo Gas

density

Temperature

adiabatic infall

shock-heate

d

cold flows

disk

Analysis of Eulerian hydro simulations by Birnboim, Zinger, Dekel, Kravtsov

Gas through shock: heats to virial temperaturecompression on a dynamical timescale versus radiative cooling timescale

11 compresscool tt

Shock-stability analysis (Birnboim & Dekel 03): post-shock pressure vs. gravitational collapse

34

521

VRt s

compress

Shock-Heating Scale

Mvir [Mʘ] 6x1011

Mʘ

Birnboim & Dekel 03; Dekel & Birnboim 06

stable shock

unstable shock

120250

300

100

Vvir [km/s]

Fraction of cold gas in halos: Eulerian simulationsBirnboim, Dekel, Kravtsov, Zinger 2006

shock heating

z=4

z=1

z=2

z=3

Fraction of cold/hot accretionSPH simulationKeres, Katz, Weinberg, Dav’e 2004

Z=0, under-estimate Mshock

sharp transition

Mvir [Mʘ]

Cold Flows in Typical Halos

redshift z

1013

1012

1011

0 1 2 3 4 5

1σ (22%)

2σ (4.7%)

shock heating

M* of Press Schechter

at z>1 most halos are M<Mshock→ cold flows

At High z, in Massive Halos: Cold Streams in a Hot

Medium

Totally hot at z<1

in M>Mshock

Cold streams at z>2

shock

no shock

cooling

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

Birnboim, Zinger, Dekel, Kravtsov

Cold flows riding dark-matter filaments

gas density

dark matter

gas temperature

M*

Mvir [Mʘ]

Cold Streams in Big Galaxies at High z

all hot

1014

1013

1012

1011

1010

109

0 1 2 3 4 5 redshift z

all cold

cold filamentsin hot medium Mshock

Mshock>>M*

Mshock~M*

the millenium cosmological simulation

high-sigma halos: fed by relatively thin, dense filaments → cold flows

typical halos: reside in relatively thick filaments, fed ~spherically → no cold flows

Dark-matter inflow in a shell 1-3Rvir

M~M* M>>M*

radial velocity

temperature

density

one thick filament several thin filaments

Seleson & Dekel

Dense radial streams into high-sigma halos

fraction of mass outside the virial radius with high density & radial

motions

fraction of halos

M>>M*

M~M*

Mvir [Mʘ]109 1010 1011 1012 1013 1014

1

0

SNUV on dust AGN + hot medium

dynamical friction in groups

photo-ionization cold hot

feedback strength

Supernova feedback is not effective in massive galaxies

AGN feedback could be effective

in massive galaxies

Most efficient star formers: Mhalo~1011-

12

Once the gas is shock heated, what keeps it hot?

Shock Heating Triggers “AGN Feedback”

Kravtsov et al.

In M>MshockEnough energy in AGNs (but no characteristic mass)Hot, dilute gas is vulnerable to AGN feedback, while cold streams are shieldedShock heating is the trigger for “AGN fdbk”

Mshock provides the threshold for shutdown, AGNs may provide long-term maintenance

dark mattergas density

temperature

dark halos Cosmological Hydro

Simulations Slyz & Devriendt 2005

dense, cooled gas clumps

a dilute medium

dark mattergas density

temperature

dilute gas is pushed away

dense clumps are

shielded

A blast wave expanding in a two-

phase medium

The clumpy cold flows themselves may provide the maintenance of

shutdown

Birnboim, Zinger, Dekel, Kravtsov

Birnboim Birnboim & Dekel& Dekel

The role of AGNs in the

shutdown may be minor

Origin of the Bi-modality

15

SN feedback vs “AGN feedback”

Dekel & Birnboim 06

ungrouped vs grouped

cold vs hot

Two Key Processes:

Hot medium → halt star formationdilute medium vulnerable to “AGN fdbk”→ shock-heated gas never cools → shut down disk and star formation

Cold flows → star burst Streams collide near center --isothermal shock & efficient cooling → dense, cold slab → star burstDisk can survive

From blue sequence to red sequence Dekel & Birnboim 06

Mvir [Mʘ]

redshift z

all cold

hot

1014

1013

1012

1011

1010

1090 1 2 3 4 5

in hot

cold

Mshock

In a standard Semi Analytic Model (GalICS)

not red enough

excess of big blue

Cattaneo, Dekel, Devriendt, Guiderdoni, Blaizot 05

z=0

data --- sam ---

color

colo

r u-

r

magnitude Mr

no red sequence at z~1

too few galaxies at z~3

star formation at low z

With Shutdown Above 1012 Mʘco

lor

u-r

magnitude Mr

Standard co

lor

u-r

magnitude Mr

colo

r u-

r

magnitude Mr

With Shutdown Above 1012 Mʘ

Environment dependence via halo mass

Bulge to disk ratio

stellar mass stellar mass

z=3

z=2

z=1

z=3

z=2

z=1

z=3

z=2

z=1

z=3

z=2

z=1

early growth & shutdown

later growth & shutdown

very bright blue z~3

~bright blue z~2

passive

How Bright Ellipticals make it to the Red Sequence

Two Types of tracks: (Cattaneo, Dekel, Faber 06)

dry mergers

early wet mergers

dry mergers

wet mergers

magnitude MV magnitude MV

Downsizing: epoch of star formation in E’s

Thomas et al. 2005

Downsizing due to ShutdownCattaneo, Dekel, Faber 2006

bright intermediate faint . central central/satellites satellites

z=1

z=1

magnitude

colo

r

in place by z~1 turn red after z~1

z=0

z=3

z=2

z=1

Mhalo>1012Mhalo>1012

Downsizing by Shutdown at Mhalo>1012

z=1

z=2

Mhalo>1012

The bright red & dead E’s are in place by z~1 while smaller E’s appear on the red sequence after

z~1

big small

z=0

small satellite

central

M*

Mvir [Mʘ]

all hot

1014

1013

1012

1011

1010

109

0 1 2 3 4 5 redshift z

all cold

cold filamentsin hot medium

Mshockbig

big red & dead already in

place by z~1

small central

small enter the red

sequence after z~1

Downsizing by Shutdown at Mhalo>1012

small satellit

e

merge into big

halo

Mvir [Mʘ]109 1010 1011 1012 1013 1014

1

0

SN AGN + hot medium

cold hot

Downsizing by Feedback and Shutdown

feedback strength

Regulated SFR, keeps gas for later star

formation in small halos

Shutdown of star formation earlier in

massive halos, later in satellites

Is Downsizing Anti-hierarchical?

big mass small mass

z=1

z=2

z=0

Merger trees of dark-matter halos M>Mmin

Upsizing of mass in main progenitorDownsizing of mass in all progenitors >Mmin

Neistein, van den Bosch, Dekel 2006

Natural Downsizing in Hierarchical ClusteringNeistein, van den Bosch, Dekel

2006Formation time when half the

mass has been assembled

all progenitors downsizing

main progenitor upsizing

EPS

Conclusions

2. Disk & star formation by cold flows riding DM filaments3. Early (z>2) big halos (M~1012) . ...big high-SFR galaxies by cold flows in hot media4. Late (z<2) big halos M>1012 (groups): . ..virial shock heating triggers “AGN feedback” . …→ shutdown of star formation → red sequence

1. Galaxy type is driven by dark-halo mass: . ..Mcrit~1012Mʘ by shock heating (+feedback & clustering)

5. Late (z<2) small halos M<1012 (field): blue disks M*<1010.56. Downsizing is seeded in the DM hierarchical clustering 7. Downsizing is shaped up by feedback & shutdown M>1012 8. Two different tracks from blue to red sequence

Thank you

Thank you

Tilted Scaling Relations by Differential Dissipative Mergers

non-dissipative

dissipative, with gas-fraction declining with mass

Dekel & Cox 2006

R

M*

3/1*MR

const.vs.

vs.

vs.

vs.

8.0

17.02

3/165.0

3/126.0

L

LLRM

MRLR

MVL

e

eee

e

e

Structural changes in dissipative

mergers

Dekel & Cox 2006

3.0

12.0

4.0

*

*

mgMM

vgVV

rgRR

m

d

e

v

d

e

r

d

e

Tilted Scaling Relations by Wet Mergers

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:

3.0

*

*12.04.0 gMMg

VVg

RR

d

e

d

e

d

e Structural changes in mergers

5.0*

*

MMM

g gas

Gradient of gas fractionconsistent with observed gradient along the blue sequence

1.0*

25.0**

3.0*

25.0*

/

M

MMM

MR

MV

Scaling relationsconsistent with the simple model of disk formation in LCDM halos

SN feedbackTop-hat model

~big disks

Dekel & Cox 2006