Cosmological evolution of galaxies and
interaction-driven fueling of AGNs
N. Menci
INAF – Osservatorio Astronomico di Roma
Galaxy Formation in a Cosmological Context
Cosmology
Formation and Growth of
Dark Matter haloes
Their Merging histories
Their properties
Connect Properties of DM haloes
To the physical processes involving
baryons
Connect Properties of DM haloes
and the baryonic processes
To the growth of Supermassive BH
and to the AGN activity
Collapse of Dark Matter haloes
from the primordial density field
The growth and merging of virialized DM haloes;
Merging of DM haloes, Substrctures
Dynamical processes involving galactic-subclumps
inside DMproperties
haloes: of the galaxy population
Observable
Dynamical
friction,
Binary aggregations
Baryonic
Processes
The gas and stellar evolution of galaxies
TheRadiative
building of
the stellar
mass content m*)
cooling
of gas
TheStar
evolution
star formation rate dm*/dt
formation
TheSupernovae
evolution offeedback
sizes
Evolution of stellar Populations
TheEmissions
evolution of the luminosity
(UV, B bands → SFR, J, K bands → m*)
ofindicators
SMBHs and
AGNs
TheGrowth
colors as
of the
specific SFR
Refueling
of
cold
gas
for
BH
The dependence of the above on accretion
the DM
Triggering
the
gas
accretion
mass scale and environment ↔ how the
Accretion
rate →and
Build
of SMBHs
baryonic
processes
BHup
accretion
to the
The bright evolution
phase, theof
AGN
feedback
cosmological
cosmic
structutres
time/t0≈0.2
1) Gravitational instability drives the evolution
of the Dark Matter density field.
2) Observed power spectrum implies larger
perturbation amplitude on smaller scales
 M   M2  M  a
c

k  2 / 
M   0 3
V. Springel
Red: stars
Blue: gas
Total mass 3 1012 Mʘ
Vrot=270 km/s
Formation time z = 0.75
Last major merger z=3
Frame size ~ 200 Kpc
Initial (z ~ 4-5) merging events involve
small clumps with comparable sizes
Disturbed morphology at high z
Major merging at z ≈ 3.
At later times, merging rate declines
Accretion of much smaller clumps
F. Governato
Hierarchical Merging of DM haloes and of Substructures
  2c 2 d d c
dP
2 
 12
(M1  M 2 , t ) 
e
 2 2
2 
dMdt
dM dt

(



)
2  2 1
2

2
N (M ) 
2  0  c (t ) d ln 
e
2
 M  d ln M

 c (t )2
2 2
Merging Rate of DM haloes
Number of Haloes with
mass M forming at given
time t
Initial (z ~4-6) merging events involve small
clumps with comparable sizes
Disturbed morphologies at high z
Last major merging at z ≈3 for M≈3 1012 Mʘ
Last major merging at z ≈ 1 for M≈5 1013 Mʘ
At later times, merging rate declines
Accretion of much smaller clumps onto the
main progenitor
z=3
z=1
z=0
The Dynamics of galactic sub-clumps within
host Dark Matter haloes
A3258
From B.Moore web page
Fdf
v
vH
DM substructures loose orbital energy
due to the gravitational drag from
f (vH )
DM particles in the common halo

v
2
2
Fdf  4 G ln   H M B(v / 2  H ) 3
v
 df
 rci
f ( )

 dyn 
2 B(1) ln 
 RH
  MH 
 

 M 
The larger is the mass of
the host halo, the longer is the
decay time
N(v,V) = NUMBER OF GALAXIES WITH
CIRC. VELOC. v INSIDE A HALO WITH VELOC. V
V’
v’
M
1
Dynamical Friction  DF   Dyn
m ln ( M / m)
v
V
Binary Merging
v”
v’
dN (v,V , t )

dt
 merg
v
V
V
 dv' dV ' N
0
V
H
(V ' , t )
v
  dV ' N H (V ' , t )
v

2G (m  m1 )  vescape 
2
2


  Pmerg   r 1 
2 
 (r  r1 )Vrel  Vrel 
dPH (V '  V , t ) N (v' ,V ' )
prob df (v' )  surv (V ) 
dV ' dt
NT (V ' )


dPH (V '  V , t ) N (v,V ' )
1  prob df (v)  surv (V ) 
dV ' dt
NT (V ' )
  dV ' N H (V ' , t )
V
1
 agg
 n agg Vrel
dPH (V  V ' , t )
N (v ' , V ' )
dV ' dt
2/3
Frequent halo merging
Promptly followed by
coalescence of galaxies
(effectve dynam. frict).
z ~2
(1-3)
- Halo merging rarer
- Longer timescale for
galaxy coalescence by
dynam. friction
- Galaxies accumulate
inside host DM haloes
The radiative cooling of gas in galaxies
The star formation from such cooled gas
The evolution of the stellar population
The feedback from SNae reheating part
of the cooled gas
2
mcool (M )  4  gas Rcool
Rcool

m*  mcool (M ) /  * (M )  * ( M )   dyn vc
t
 * (t  t ' )   (t ' ) dt '
S   m
0
mh  m* ESN # SN / v 2
SEMI-ANALYTIC MODELS OF
GALAXY FORMATION
Kauffman et al. 93 ; Cole et al. 94; Somerville & Primack
00; Cole et al. 00; NM et al. 02; Wu, Fabian, Nulsen 00
DYNAMICAL EVOLUTION OF
DARK MATTER CONDENSATIONS
DYNAMICAL EVOLUTION OF
DARK MATTER CONDENSATIONS
*
Given M, z of DM haloes:
Halo properties
Average density
Virial temperature
Virial radius
Density profile
Gas properties
Profiles
Cooling
Disk
Star Form. Rate
SNae Feedback
Evolution of
Stellar Populations
Given M, z of DM haloes:
Average density
Virial temperature
Virial radius
Density profile
  180 u

Halo properties
 c  crit
Navarro Frenk White 1997
2
(r / rs ) (1  r / rs )
Profiles
Cooling
Disk
1/ 3
 3M 

rvir  
 4  
kTv ( M )   m p
Gas properties
GM
rvir
Star Form. Rate
SNae Feedback
Evolution of
Stellar Populations
Given M, z of DM haloes:
dp
GM
 
d
r2
Halo properties
Average density
Virial temperature
Virial radius
Density profile

kT
GAS p gas 
 mp
DM
pDM   2

 gas   DM
m p 2

kT
Gas properties
Profiles
Cooling
Disk
Star Form. Rate
SNae Feedback
Evolution of
Stellar Populations
Given M, z of DM haloes:
 cool
3  gas (r)
kT

2  m p ne2 (r ) (T )
rcool = radius enclosing the region where tcool ≤ tH(z)
2
mcool (M )  4   gas (r ) rcool
rcool
rcool reset to zero after major merging events
Halo properties
Average density
Virial temperature
Virial radius
Density profile
Gas properties
Profiles
Cooling
Disk
Star Form. Rate
(when Mprog < ½ Mmerger)
SNae Feedback
Evolution of
Stellar Populations
Given M, z of DM haloes:
Halo properties
DM angular momentum J aquired from tidal
torques due to surrounding perturbations
  J / J circ  JE1/ 2G 1M 5 / 2
Average density
Virial temperature
Virial radius
Density profile
  0.01  0.08
Assume that, durung collapse, the ratio jgas=Jgas/J
is conserved
Assuming an exponential Surf. Density Profile
( R)  0 exp(  R / Rd )
Gas properties
Profiles
Cooling
Disk
Assuming centrifugal balance
J gas  2  Vc ( M )( R) R 2 dR
DM
Mo, Mao, White 1997
1  j gas 
rd 
 Rvir ( M )


2  mgas 
mgas 
mcold
mDM
gas
Given M, z of DM haloes:
mcool ( M )
m * 
 * (M )
with
mcool ( M )  ( M )   rdisk
m * 
*
SF
vdisk
 * (M )
1.4
Cf. with Shmidt law
m *  mcold
log SFR/Area
m *  mcold
log GAS Surf. Density
m *  mcold 


Area  Area 
mcold

char. time
m
  cold
d
Halo properties
Average density
Virial temperature
Virial radius
Density profile
Gas properties
Profiles
Cooling
Disk
Star Form. Rate
SNae Feedback
Evolution of
Stellar Populations
Given M, z of DM haloes:
m*
ESN  10  IMF  0
M
kTSN  ESN / mgas  0.1 keV
51
Halo properties
Average density
Virial temperature
Virial radius
Density profile
Gas properties
Number of SNae produced per unit stellar
3
mass (depends on IMF)  IMF  2  5 10
Fract. of SN energy dumped into gas
0≈0. 1
ESN
m *
m reheat  2  2
vc
vesc
Profiles
Cooling
Disk
Star Form. Rate
SNae Feedback
Evolution of
Stellar Populations
Given M, z of DM haloes:
Halo properties
Average density
Virial temperature
Virial radius
Density profile
The integrated emission (at wavelength ) from
stellar populations is computed after convolving
the Spectral Energy Distributions (, Bruzual &
Charlot 1993) with the resulting SFR in all the
progenitor haloes of the considered galaxy
Gas properties
Profiles
Cooling
Disk
t
 * (t  t ' )   (t ' ) dt '
S   m
Star Form. Rate
0
SNae Feedback
Evolution of
Stellar Populations
Given M, z of DM haloes:
  200 c
 (r)
Tvir(M)
gas (r)
vc (M )
mcool ( M )  4 
Navarro, Frenk, White 1997
 gas  

DM
m p 2

kT
2

(
r
)
r
dr
 gas
0
vd (M, z) d=rd / vd
m *  mcold
mcold

d
ESN
m *
m reheat  2  2
vc
vesc
t
 * (t  t ' )   (t ' ) dt '
S   m
0
Average density
Virial temperature
Virial radius
Density profile
Gas properties
rcool
rd (M, z)
Halo properties
Profiles
Cooling
Disk
Mo, Mao White 1998
Star Form. Rate
SNae Feedback
Evolution of
Stellar Populations
5)
1)
2)
4)
Consider
For
Compute
each
of
astar
cooled
grid
them
formation
ofmass
construct
DMamhalo
rate
the
masses
mthe
/t*disk
and
atWhence
size
z=0.
history
Their
the aboundance
3) At
the
bottom,
assign
baryon
mass
initially
c and
cmerging
bM,
is
give by
massT:stars
function
assumed
virial
mh=inWtimestep
amount
ofatPS
formed
m*= mc/t* t
bM
6) Computed SN feedback and reheat part of mc
to virial temp.
7) Make 1 timestep upward along the merging tree
8) In the new halo compute dyn. frict. and
aggregation timescales. If galaxies aggregate,
merge their gas and stellar content (mh, mc, m*)
 df
 rci
f ( )

 dyn 
2 B(1) ln 
 RH
  MH 
 

 M 
10)Iterate
9)
For each
from
galaxy,
step 4 (compute cooling in new haloes,
star
formation,
feedback
the star
formation
history …)
in all its
progenitor galaxies can be computed
at all earlier times
and the integrated emission due to
stellar populations formed at all
earlier times can be computed
t
 * (t  t ' )   (t ' ) dt '
S   m
0
Data
a) Zwaan et al. 1997
b) Cole + 2001, Bell +, 2003
c) Giallongo et al. 00
d) Mattewson et al. 92
Willick 96
Giovannelli 97
e) Blanton et al. 00
Madgwick et al. 02
Zucca et al.97
f) Steidel et al. 97
Somerville et al. 99-01
The Cosmic Star Formation Rate
Z
At high z large m * 
mcool ( M )
 * (M )
•Rapid cooling + gas
replenishing due to frequent
merging→ large mcool
•Short Star Form. Timescales
r
 * ( M )   SF disk  (1  z ) 1/ 2
vdisk
1013 Mʘ
rdisk  rvir  ( M /  )1/ 3
vdisk  (GM / rvir )1/ 2  M 1/ 3  1/ 6
* 
rvir
  1/ 6  (1  z ) 1/ 2
vdisk
109 Mʘ
Z
t1
t2
small mass
halo
t3
Large mass
halo
z=0
Massive galaxies originate from the
merging of clumps which have collapsed
in biased, high-density regions of the
density field, hence at higher redshift.
The star formation histories
of the population contained (today)
in massive galaxies
peaks at higher redshift
compared to that of smaller galaxies
m *
high
m*
Low-mass galaxies
High-mass
galaxies
At
high-redshift,
cold gas
At high
z>2, SF proceeds
at
effectively
expelled
extremely high
rates by feedback
Suppressed
at high –z
Feedback isSF
ineffective
in
suppressing star formation
At lower z, haloes grow and
feedback
less effective
Rapid gasbecomes
consumption
m *
low
m*
Cold
available
low-z
Cold gas
gas left
exhausting
at at
z~2
Star
active
at low
Star formation
formation still
drops
thereafter
Smooth
SF history
Local galax.:
gas poor, old stars
large mass
small mass
Bimodal Color Distribution
Bright
Red Galaxies
Faint
Blue Galaxies
Baldry et al. 2004
Color Distribution Dependence on luminosity
BLUE
RED
 * (M )  const. in mass
 * ( M )   SF
rvir
vvir
m ( M )
m *  cool
 * (M )
 m 

 * ( M )  f 
 mcold 
 * ( M )   SF
rdisk
vdisk
1  j gas 
rd 
 Rvir ( M )


m
2  gas 
The cold gas fraction
log Number
log Number
Local galaxies with u-r<1.3
-20.5 < Mr <-19.5
Local galaxies with u-r>2.3
vc2 feedback   0 ESN  100 km / s
M=109 Mʘ at z=4.5
Mprog=109 Mʘ
Color Distribution: Dependence on the environment
t1
t2
small mass
halo
t3
Large mass
halo
z=0
Galaxies endng up in clusters
originate from the merging of
clumps which have collapsed in
biased, high-density regions of the
density field, hence at higher
redshift.
The star formation histories
of the population contained (today)
in dense environments
(groups/clusters)
peaks at higher redshift
compared to that of smaller galaxies.
Bimodality extends at least up to z ≈ 0.8
z=1.3
Bell et al. 03
1)The downsizing is naturally predicted in hierarchical models: it
originates from the properties of the primordial density field
(biasing).
EROS
2) The bimodality in the color distribution originates from the interplay
between the above biasing properties of the density field and the
non-gravitational mass scale defined by the SNae feedback
BUT
The PARTITION between the faint/Blue and the massive/red galaxies is
not correctly reproduced especially at high - z
The abundance of massive red galaxies at higher redshift
results from a balance between
a) the earlier epoch of star formation in their progenitors (due to the
denser environment where the formed) + their faster exhaustion of gas
b) the lower abundance of massive galaxies at higher z
The Co-evolution of AGNs and its feedback on
galaxy evolution
The Circumnluclear Starbursts and AGN accretion
Triggered by Galaxy Encounters
‘”tidal forces during encounters
cause otherwise stable disks to
develop bars, and the gas in such
barred disks, subjected to strong
gravitational torques, flows toward
the central regions “
Mihos & Hernquist 1996
See also Noguchi 1987
Barnes & Hernquist 1991
Gas Angular Momentum
Part of the available galactic cold gas is detabilized and
funnelled toward the centre
1 j 1 m' rd vd Cavaliere
f ( v, V ) 

Vittorini
2 j
2 mbV
2000
(Sanders & Mirabel 96)
Governato 05
1/4 feeds central BH
QSO Properties
Interaction rate
2
 1  n ( rtidal
) Vrel
FlyBy
m acc (v, t ) 
1 f mcold
4
r
c 2 macc
L ( v, t ) 

t
mBH  (1   )  m acc (v, t ' ) dt '
0
3/4 feeds
circumnuclear starbursts
Starbursts Properties
m * (v, t ) 
t
3 f mcold
4
r
 * (t  t ' )   (t ' ) dt '
S   m
0
Encounter Rate
Gas Mass destabilized / Accreted
2
 1  n ( rtidal
) Vrel
 acc 
m
FlyBy
n  1 / R3
Strongly increases with z
2
r
Strongly increases with z
larger m’/m ratios
Larger vd/V ratio
Shorter r~(1+z)-1/2
Larger cold gas mass
2
 r  Vrel  r  1
    dyn
R R R
 1   
FlyBy
f mcold
Larger r/R ratio
Larger
f ≥ 0.01
Shorter r ∝ (1+z)-1/2
1 j 1 m' rd vd
f ( v, V ) 

2 j
2 mbV
Cavaliere
Vittorini
2000
This occurs at a rate 
 n ( rtidal ) Vrel and is averaged over all merging
FlyBy
partners (m’) in the same group/cluster (with circ. veloc. V) at inpact param. b
These quantities + the cold available gas mcold are obtained from the SAM (NM et al. 2002)
1
m acc (v, t ) 
f mcold
r
Accretion rate
2
c 2 macc
L ( v, t ) 

Bolom. Luminos.
t
mBH  (1   )  m acc (v, t ' ) dt '
0
BH mass
The Bursts
EROs
BURSTS
Enhance star formation at z≥4 in massive obsejcts (MZ<25.5)
as to match the stellar mass distribution up to z=1.5
MZ ≤ 25
NM, Cavaliere, Fontana,
Giallongo, Poli, Vittorini 2004
MBH~4
Cold gas mass ~ 2.
Interactions favour large
galact. masses → 3.
SN feedback disfavour small
galact. masses → 3.8
The normalization of the QSO LFs
- increases from z=0 to z=2
- decreases for z>2
z=4
z=3
z=2
z=1.2
z=0.5
The rise with z of the
normalization
is due to the increasing
fraction of destabilized cold
gas feeding the BH
BECAUSE
The encounter rate and
the hence the accretion
rate increases with z
Data from Hartwick & Shade 1990, Boyle et al 2000,
Fan et al 2001
The normalization of the X-ray LFs
-increases from z=0 to z=2
-Stronger evolution for brighter objects
The rise with z of the normalization
is due to the increasing fraction of
destabilized cold gas feeding the BH
BECAUSE
The encounter rate and the hence
the accretion rate increases with z
Data from Fiore et al. 2003 (Hellas)
z=3
Data from Ueda
et al. 2003
The rapid evolution of bright AGNs
is due to the rapid exaustion of
galactic cold gas in massive galaxies,
whose star formation is peaked at
higher z
NM, Fiore, Perola,
Cavaliere 2004
Assuming an X-ray Bol. Corr.C2-10 keV=80
Comparison / Predictions for AGN in X-rays
The
Number/Luminosity
AGN
downsizingDensity
The rapid decrease at z<2.5 is
due to 3 concurring factors
1) The decrease with time of the
merging rate of galaxies;
merging events replenish the cold gas
content of the galactic halo.
2) The decrease with time of the
galactic cold gas left available for
accretion
3) The decrease with time of the
encounter rate stimulating the
funneling of part of the cold gas
toward the nucleus
-Milder evolution (at z<1.5-2) for the low-luminosity sources, as expected in HC
-Bright QSOs formed on shorter timescales at higher z
t1
t2
small mass
halo
t3
Large mass
halo
z=0
Massive galaxies (larger SMBHs)
originate from the merging of clumps
which have collapsed in biased, highdensity regions of the density field,
hence at higher redshift.
1) massive galaxies (at z=0) have
converted their gas into stars at z>2
(higher redshift) compared to that of smaller
galaxies: Faster exhaustion of gas at z<2
2) The denser environment where the
progenitors formed favours encounters at hig
→ enhanced AGN activity at high z
Log L / LEdd
AGN feedback:
The Blastwave model
n(r)
Cavaliere et al. 02; Lapi et al. 05
Rp Rs
f=10-3 – 10-2
R
r
The colors of massive galaxies
Including AGN feedback
Color-Magnitude Distribution
AGN feedback is NOT at the
origin of the downsizing and of
the local bimodality
Rather, it affects the partition of
galaxies enhancing the fraction of
red objects at higher redshifts
NO AGN feedback
AGN feedback
Bimodal Distribution
with populated red
branch present by z=2.5
The aboundance of EROs (R-K>5, Vega system)
z=1.5-2.5
Data from GOODS
(from Somerville et al 04
green histograms)
Data
Datafrom
Cimatti et al. 02
Roche
Dunlop
Almaini
(purple
histogram)
(2003 triangles) and Daddi
et al. (2000,squares)
The aboundance of DRGs (J-K>2.3, Vega system)
The white line refers to
predictions when no dust is
included in the model
Low-z population contributed
by obscured objects
High-z population mainly
contributed by galaxies with
evolved stellar populations
GOODS data from Grazian 06
(points upper panel and green
hiistogram)
and
Papovich 06
(cyan histogram);
the latter refers to galaxies selected
by stellar mass m*>1011 Mʘ)
R
2
LX  T 1/ 2  dr  gas
(r )
0
LX  T R 
1/ 2
3
LX  T 
1/ 2
DM
2
2
DM
( z )   gas /  DM  dx
2
( z )   gas /  DM  dx
2
Depends on
m p
KTvir


KT
KT
2
Temperature of gas heated by the
gravitational potential
Temperature of gas (includes the
Contribution from SNae & AGNs)
The larger the energy injection, the lower β → extended profiles
→ lower central densities → lower Lx
LX  T 
2

1/ 2
DM
( z )   gas /  DM  dx
m p 2
KT
2
KTvir

KT
T TTTvirTTvir
vir
 TAGN
TSNTSN
1) At z>2.5
● rapid merging, frequent encounters
and rich reservoirs of galactic cold gas
continuously replenished by merging
- BHs accrete at full Eddington rate
- Rapid Star formation
●Effective starbursts (up to 103 Mʘ/yr)
- Rapid build-up of SMBHs
particularly in biased density
regions (progenitors of local
large-mass SMBHs)
2) At z<2
i) The construction of galaxies
and the merging rate decline
ii) decline of accreted fraction f ≈ j / j
iii) exaustion of cold gas
particulary in massive galaxies
- Self-regulated star form. in
progenitors of low-mass galaxies
(originated from the merging of clumps
collapsed in biased, high-density regions
where most of the gas has already been
converted into stars)
● Massive galaxies (MDM > 1013 Mʘ) undergo an
almost passive evolution → redder colors
● Small-mass galaxies still star forming
● QSO only occansionally refueled
● Emission drops down to L~ 10-2 LEddington
The Global Picture
- Rapid star form. in progenitors
of massive galaxies
- Rapid enrichment of interg. gas
- Starburst may convert most of
the available gas
Evolutinary Tracks
EROs
Galaxies with
DM mass of:
(at lower z)
M=1013 M⊙
M=1012inM⊙
- AGN feedback effective
11 M
M=2.5
10
⊙
expelling gas
10
M=5 10 M⊙
1) At z>2.5
● rapid merging, frequent encounters
and rich reservoirs of galactic cold gas
continuously replenished by merging
- BHs accrete at full Eddington rate
- Rapid Star formation
●Effective starbursts (up to 103 Mʘ)
2) At z<2
i) The construction of galaxies
and the merging rate decline
ii) decline of accreted fraction f ≈ j / j
iii) exaustion of cold gas
particulary in massive galaxies
(originated from the merging of clumps
collapsed in biased, high-density regions
where most of the gas has already been
converted into stars)
● Massive galaxies (MDM > 1013 Mʘ) undergo an
almost passive evolution → redder colors
● Small-mass galaxies still star forming
● QSO only occansionally refueled
● Emission drops down to L~ 10-2 LEddington
The Global Picture
- Rapid fading of both bright
AGNs and large-mass galaxy
population
- Downsizing
Evolutinary Tracks
Galaxies
with DM mass of:
- Bimodal
color distribution
13 M
M=10
-AGN numb. (and lumin.) 12 ⊙
M=10rapidly
M⊙
density evolving more
11
for bright AGNs M=2.5 10 M⊙
M=5 1010 M⊙
Stellar mass in place in massive galaxies at z>2
Downsizing of AGNs: peak moving to lower z for fainter AGNs
Aboundance of EROs
SCUBA sources
Substructures in DM haloes
AGN feedback effects on colors and stellar mass of galaxies ?
‘’Quantitative’’ downsizing
Residual fraction of bright (Mr≈-22) galaxies with blue colors
Seed BH of mass 100 M in haloes with mass-resolution-limit ?
Aboundance of satellite BHs ?
SFR
Self-Regulated
Regime
m* 
 m
mcc f (mmcold
Wb/ /mW)
m*  mc
(Dekel & Silk 05)
vc  100 km / s
Circular Vel. Of
Progenitors