Date post: | 21-Dec-2015 |
Category: |
Documents |
View: | 215 times |
Download: | 0 times |
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~3x1010M
ʘ
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 expansion
Halo 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
3
4
5
21
V
Rt scompress
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 simulations
Birnboim, Dekel, Kravtsov, Zinger 2006
shock heating
z=4
z=1
z=2
z=3
Fraction of cold/hot accretion
SPH simulation
Keres, 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
MshockMshock>>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>Mshock
Enough energy in AGNs (but no characteristic mass)
Hot, dilute gas is vulnerable to AGN feedback, while cold streams are shielded
Shock heating is the trigger for “AGN fdbk”
Mshock provides the threshold for shutdown, AGNs may provide long-term maintenance
dark matter
gas density
temperature
dark halos
Cosmological Hydro Simulations Slyz & Devriendt
2005
dense, cooled gas clumps
a dilute medium
dark matter
gas 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 burst
Disk can survive
From blue sequence to red sequence Dekel & Birnboim 06
Mvir
[Mʘ]
redshift z
all cold
hot
1014
1013
1012
1011
1010
109
0 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
Mshock
big
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 Clustering
Neistein, van den Bosch, Dekel 2006
Formation 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*<1010.5
6. 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
*
*
mgM
M
vgV
V
rgR
R
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 gM
Mg
V
Vg
R
R
d
e
d
e
d
e Structural changes in mergers
5.0*
*
MM
Mg 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 feedback
Top-hat model
~big disks
Dekel & Cox 2006