Transcript Formation of Dwarf/LSB Galaxies

Origin of E vs S Galaxies
Bi-modality and Downsizing
Avishai Dekel
HU Jerusalem
Bernard’s Cosmic Stories, Valencia, June 2006
A third type of Bernard’s students:
Those who were inspired by Jones’ 1976 review
Summary
Q: z<2: Bright, red & dead, E’s. No big blues.
………….Bi-modality, environment dependence
A: Shutdown in Mhalo>1012
Trigger: virial shock heating (threshold mass) …
Birnboim & Dekel 03
…..Maintenance: “AGN feedback” (?)
Dekel & Birnboim 06
Cattaneo, Dekel et al. 06
Q: z~2-4: Massive, high-SFR disks(?)
A: Cold flows (+mergers) even in Mhalo~1012
Seleson & Dekel 06
Q: Downsizing?
Neistein, van den Bosch
A1: Not anti-hierarchical for DM halos !
& Dekel 06
A2: Feedback in Mhalo<1012 & the shutdown in Mhalo >1012
Cattaneo, Dekel, Faber 06
Q: From the blue to the red sequence
A: Two tracks: early/late shutdown, wet/dry mergers
Dekel et al. 05; Dekel & Cox 06
Bi-modality in color, SFR, bulge/disk
0.65<z<0.75
E/S0/Sa
Disks and Irregulars
M*crit~3x1010Mʘ
Bell
Color-Magnitude bimodality & B/D
depend on environment ~ halo mass
environment density: low
high
very high
disks
spheroids
Mhalo<6x1011
SDSS: Hogg et al. 03
“field”
Mhalo>6x1011
“cluster”
Downsizing
0.65<z<0.75
E/S0/Sa
z<1
z~1
Disks and Irregulars
Bell
z~1
z~3
Standard Picture of Infall to a Disk
Rees & Ostriker 77, Silk 77, White & Rees 78, …
Perturbed expansion
Halo virialization
shock heating
at the virial radius
Gas infall,
Radiative cooling
Accretion to disc if tcool<tff
Stars & feedback
M<Mcool ~1012-13M⊙
Growth of a Massive Galaxy
1011M
ʘ
T °K
1012Mʘ
shock-heated gas
“disc”
Spherical hydro simulation
Birnboim & Dekel 03
A Less Massive Galaxy
T °K
1011Mʘ
cold infall
shocked
“disc”
Spherical hydro simulation
Birnboim & Dekel 03
Hydro Simulation: ~Massive M=3x1011
Kravtsov et al.
virial shock
z=4
M=3x1011
Tvir=1.2x106
Rvir=34 kpc
virial shock
Less Massive M=1.8x1010
Kravtsov et al.
cold
infall
z=9
M=1.8x1010
Tvir=3.5x105
Rvir=7 kpc
virial
radius
Mass Distribution of Halo Gas
disk
cold flows
density
shockheated
adiabatic infall
Temperature
Analysis of Eulerian hydro simulations by Birnboim, Zinger, Dekel, Kravtsov
Gas through shock: heats to virial temperature
compression on a dynamical timescale
versus radiative cooling timescale
Shock-stability analysis (Birnboim & Dekel 03):
post-shock pressure vs. gravitational collapse
1
cool
t
1
compress
t
tcompress
21  4 Rs


5  3 V
Shock-Heating Scale
Birnboim & Dekel 03;
Dekel & Birnboim 06
stable shock
Mvir
6x1011 Mʘ
[Mʘ]
300
120
250
unstable shock
100
Vvir
[km/s]
Fraction of cold gas in halos: Eulerian simulations
Birnboim, Dekel, Kravtsov, Zinger 2006
shock
heating
z=4
z=3
z=2
z=1
Fraction of cold/hot accretion
SPH
simulation
Keres, Katz,
Weinberg,
Dav’e 2004
sharp
transition
Z=0, underestimate Mshock
Cold Flows in Typical Halos
1013
Mvir
shock heating
1012
[Mʘ]
2σ (4.7%)
M* of Press
1011
Schechter
at z>1 most halos are
M<Mshock→ cold flows
1σ (22%)
0
1
2
3
redshift z
4
5
At High z, in Massive Halos:
Cold Streams in a Hot Medium
in M>Mshock
Totally hot
at z<1
shock
Cold streams
at z>2
cooling
no shock
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
Cold Streams in Big Galaxies at High z
1014
1013
Mvir
[Mʘ]
all hot
1012
cold filaments
in hot medium
Mshock~M
Mshock>>M*
*
all cold
1011
1010
109
Mshock
M*
0
1
2
3
redshift z
4
5
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 1-3Rvir
Seleson & Dekel
density
temperature
one thick filament
several thin filaments
radial velocity
M~M*
M>>M*
Dense radial streams into high-sigma halos
M~M*
fraction of
halos
M>>M*
fraction of mass outside the virial radius
with high density & radial motions
Once the gas is shock heated, what keeps it hot?
1
feedback
strength
cold hot
photo-ionization
UV on dust
SN
AGN + hot medium
AGN feedback
could be
effective
dynamical
friction
massive galaxies
iningroups
Supernova feedback
is not effective in
massive galaxies
0
Most efficient star formers: Mhalo~1011-12
109
1010
1011
1012
Mvir [Mʘ]
1013
1014
Shock Heating Triggers “AGN Feedback”
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”
Kravtsov et al.
Mshock provides the threshold for shutdown,
AGNs may provide long-term maintenance
dark halos
Cosmological Hydro Simulations
Slyz & Devriendt 2005
dark matter
gas density
dense, cooled gas clumps
a dilute medium
temperature
A blast wave expanding
in a two-phase medium
dark matter
gas density
dilute gas is
pushed away
dense clumps
are shielded
temperature
The clumpy cold flows themselves may
provide the maintenance of shutdown
Birnboim
& Dekel
The role of AGNs
in the shutdown
may be minor
Birnboim,
Zinger,
Dekel,
Kravtsov
Origin of the Bi-modality
Dekel & Birnboim 06
cold
vs
hot
ungrouped
vs
grouped
SN feedback
15
vs
“AGN feedback”
Two Key Processes:
Cold flows → star burst
Streams collide near center -isothermal shock & efficient cooling
→ dense, cold slab → star burst
Disk can survive
Hot medium → halt star formation
dilute medium vulnerable to “AGN fdbk”
→ shock-heated gas never cools
→ shut down disk and star formation
From blue sequence to red sequence
1014
1013
Mvir
[Mʘ]
cold
hot
1012
Mshock
in hot
1011
all cold
1010
109
0
1
2
3
redshift z
4
5
Dekel & Birnboim 06
In a standard Semi Analytic Model (GalICS)
z=0
Cattaneo, Dekel, Devriendt, Guiderdoni, Blaizot 05
excess of big blue
no red sequence at z~1
data --sam ---
color
not red enough
too few galaxies at z~3
color u-r
star formation at low z
magnitude Mr
color u-r
With Shutdown Above 1012 Mʘ
magnitude Mr
color u-r
Standard
magnitude Mr
color u-r
With Shutdown Above 1012 Mʘ
magnitude Mr
Environment dependence
via halo mass
Bulge to disk ratio
How Bright Ellipticals make it to the Red Sequence
Two Types of tracks:
(Cattaneo, Dekel, Faber 06)
early growth & shutdown
passive
later growth & shutdown
z=1
z=2
z=1
z=3
z=2
z=3
~bright blue
z~2
very bright
blue z~3
magnitude MV
magnitude MV
dry mergers
z=1
z=2
early wet
mergers
stellar mass
z=3
dry mergers
wet mergers
z=1
z=2
z=3
stellar mass
Downsizing: epoch of star formation in E’s
Thomas et al. 2005
Downsizing due to Shutdown
bright
.
central
Cattaneo, Dekel, Faber 2006
intermediate
faint
satellites
central/satellites
z=0
z=1
color
z=2
z=1
z=1
z=3
magnitude
in place by z~1
turn red after z~1
Downsizing by Shutdown at 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
z=2
Mhalo>1012
Mhalo>1012
small satellite
big
z=1
Mhalo>1012
small central
z=0
Downsizing by Shutdown at Mhalo>1012
1014
Mvir
big red & dead
already
in place
all hot
by z~1
1013
cold filaments
in hot medium
[Mʘ]
1012
big
1011
small
central
small enter the
red sequence
after z~1
merge into
big halo
1010
109
small
satellite
M*
all cold
0
1
Mshock
2
3
redshift z
4
5
Downsizing by Feedback and Shutdown
cold hot
1
SN
feedback
strength
0
Regulated SFR, keeps gas
for later star formation
in small halos
109
1010
1011
AGN + hot medium
Shutdown of star formation
earlier in massive halos,
later in satellites
1012
Mvir [Mʘ]
1013
1014
Is Downsizing Anti-hierarchical?
Merger trees
of dark-matter
halos M>Mmin
z=2
z=1
Upsizing of mass
in main progenitor
Downsizing of mass
in all progenitors >Mmin
Neistein, van den
Bosch, Dekel 2006
z=0
big mass
small mass
Natural Downsizing in Hierarchical Clustering
Neistein, van den Bosch, Dekel 2006
Formation time
when half the
mass has been
assembled
EPS
all progenitors
downsizing
main progenitor
upsizing
Conclusions
1. Galaxy type is driven by dark-halo mass:
. ..Mcrit~1012Mʘ by shock heating (+feedback & clustering)
2. Disk & star formation by cold flows riding DM filaments
3. Early (z>2) big halos (M~1012)
. ...big high-SFR galaxies by cold flows in hot media
4. Late (z<2) big halos M>1012 (groups):
. ..virial shock heating triggers “AGN feedback”
. …→ shutdown of star formation → red sequence
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
Dekel & Cox 2006
 e  L0.26
vs. V  M 1/ 3
Re  L0.65
vs. R  M 1/ 3
M e   e Re  L0.17
2
non-dissipative
vs. L
R  M*1/ 3
 e  L0.8 vs.   const.
R
dissipative, with gas-fraction
declining with mass
M*
Structural changes in
dissipative mergers
Re
 gr
Rd
r  0.4
Ve
 gv
Vd
v  0.12
M *e
 gm
M *d
m  0.3
Dekel & Cox 2006
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.
Structural changes in mergers
Re
 g 0.4
Rd
Ve
 g 0.12
Vd
M *e
 g 0.3
M *d
The predicted properties of the progenitors:
Scaling relations
consistent with the simple model
of disk formation in LCDM halos
V  M*
0.25
R  M*
0 .3
M / M*  M*
  M *  0 .1
Gradient of gas fraction
consistent with observed
gradient along the blue sequence
g
M gas
M*
~big disks
 0.25
SN feedback
Top-hat model
 M*
0.5