Low-mass galaxies At high-redshift, cold gas effectively expelled by feedback Suppressed SF at high –z At lower z, haloes grow and feedback becomes less effective Cold gas left available at low-z Star formation still active at low z Smooth SF history * * m m high * * ow m m l High-mass galaxies At high z>2, SF proceeds at extremely high rates Feedback is ineffective in suppressing star formation Rapid gas consumption Cold gas exhausting at z~2 Star formation drops thereafter Local galaxies are gas poor with old stars
Transcript
Low-mass galaxies
At high-redshift, cold gas effectively expelled by feedback
Suppressed SF at high –z
At lower z, haloes grow and feedback becomes less effective
Cold gas left available at low-z
Star formation still active at low z
Smooth SF history
*
* m
mhigh
*
* owm
ml
High-mass galaxies
At high z>2, SF proceeds at extremely high rates
Feedback is ineffective in suppressing star formation
Rapid gas consumption
Cold gas exhausting at z~2
Star formation drops thereafter
Local galaxies are gas poor with old stars
small masslarge mass
Observations show:
A sharp transition in the physical properties of galaxies at M* ~ 3 1010 Mʘ (see, e.g., Kauffmann et al. 2003)
Tully, Mould, Aaronson 1982
• Massive galaxies are redder• Contain older stars • star formation much larger at high redshitfs
Bimodal Color Distribution
Baldry et al. 2004
BrightRed Galaxies
FaintBlue Galaxies
Color Distribution Dependence on luminosity
BLUE
RED
log Numberlog Number
Local galaxies with u-r<1 Local galaxies with u-r>1.5-20.5 < Mr <-19.5
The cold gas fraction
Mprog=109 Mʘ
skmEv SNfeedbackc /10002
M=109 Mʘ at z=4.5
Colore Distribution: Dependence on the environment
t1
t2
t3
Z=0
Large masshalo
small masshalo
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
Bell et al. 03
estimates fromGlazebrook et al. (GDDS)Rudnick et al. (FIRES)Dickinson et al. (HDFN)Fontana et al. (K20)Bell et al. (COMBO)
The Evolution of luminosity and mass functionsi) density evolution, typical of hierarchical clustering, (mass of galaxies increases with time)
ii) luminosity evolution (SFR increasing with z from z=1 to z=2.5, flat at higher z)
i) density evolution, typical of hierarchical clustering (mass of galaxies increases with time)
The Luminosity Evolution
I:Luminosity evolution: B and UV- B-band and UV luminosity ~ instanteneous star form. rate
- Star Formation strongly increases with z
- The number of massive objects decreases with z (hierarchical clustering)
M
NZ=0Z=3
*mLB
II: Luminosity evolution: K
- K-band luminosity ~ total mass in stars formed at current time
*
0
*
0
*
')'( )'(
')'()'(
mdtttmSconstt
dttttmS
t
t
At z ~ 1.5 simple models underpredict the total amount of stars formed in massive haloes
Additional mechanism MUST BE triggering star formation at z≥4
‘”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 “
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Part of the available galactic cold gas is detabilized and funnelled toward the centre
Cavaliere Vittorini 2000
Rate:
tidalrelr rV /1 Duration:
reltidal VrnFlyBy
)( 21
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j
jVvf dd'
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Part of the available cold gas is detabilized and funnelled toward the centre
Cavaliere Vittorini 2000
(Sanders & Mirabel 96)
Starbursts Mass Conversion rate
r
coldmftvm
4
3),(*
Strongly increases with z
larger m’/m ratios
Larger vd/V ratio
Smaller r~(1+z)-1/2
Larger cold gas mass
Larger f ≥ 0.01
Starbursts Freqency
reltidal VrnFlyBy
)( 21
Strongly increases with z
Larger r/R ratio
Smaller r~(1+z)-1/2
3/1 Rn
122
1
dynFlyBy R
r
R
V
R
r rel
The Bursts
EROs
AGN activity triggered by destabilization of gas during encounters:
Would naturally explain
1) They are already in place at high z (at least at z=2, see McLure talk) while the stellar content of galaxies is still growing
II) Their activity drops at lower z
Burst constitute only one mode of star formation addig to quiescent star formationBUT for AGN constitute the whole feeding mechanism
Cold Gas destabilization from Fly-by interactions strongly decreases from z=3 to z=0
At high z a large amount of cold gas is destabilized
Strong starbursts are expected at z > 3-4
The effect of Starbursts on the Galaxy Lum. Function.
MZ < 25.5
L > 0.2 L*
Data from Giavalisco et al. 03
Somerville Primack & Faber 2001
The effect of Starbursts induced by fly-by events in the K-band observables
K-band Lumin. Functions
K-band z-counts
NM et al 2004
z=1-1.6
z=1.6-2
z=2-3
Stellar Mass function at high z
At z > 2.5 – 3-Effective cooling (low virial T≈105 K, high densities)-rapid merging, frequent encounters allow continuous refueling of gas in the growing galactic haloes. -High SFR (≈102 Mʘ/yr), especially in clumps formed in BIASED regions of the density field (progenitors of large-mass galaxies / cluster members.-Self-regulated SF: in small-mass clumps (M<109 Mʘ) feedback yields a self-regulated star-formation
-Frequent encounters continuously destabilize an appreciable fraction of such a gas triggering: - fast BH accretion: QSO at full Eddington rate - Powerful starbursts (up to 103 Mʘ / yr)- Building-up of the stellar mass conent
At z < 2. i) Construction of galaxies and merging rate declineii) Accretion of smaller lumps by major progenitors iii) decline of fraction f ≈ j / j of gas accreted by BH or converted in SBurstsiv) exaustion of cold gas 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)
v) Lower-mass haloes (MDM > 5 1011 Mʘ) still star forming
vi) Starbursts activity drops especially in massive systems- QSO only occasionally refueled by encounters- Emission drops down to L~ 10-2 LEddington- QSO Lum. Funct. steepens at bright end
Arising of bimodality in the properties of galaxy pop.
• Massive galaxies (MDM > 1013 Mʘ) undergo an almost passive evolution redder colors.• Residual star formation in less massive galaxies (rates 0.1 – 1 Mʘ/yr) still retaining part of theircold gas reservoir (blue colors)
preferentially in massive haloes with larger cross section for interactions.
Large B/ UV EmissionLy-break glxs
1/3 of the stellar mass in galaxies with M*>1010 Mʘ is in place at by z≈2
What about z≈3 ?
The Big Picture
Bibliografia
I. Evoluzione delle Perturbazioni Cosmologiche 1. E. Bertschinger, Annu. Rev. Astron. Astrophys. 1998. 36: 599-6542. Coles, P., Lucchin, F."Cosmology - The origin and evolution of Cosmic Structure", 1995, Wiley, Chichester.3. Efstathiou, G., Silk, J.I., 1983, Foundamental Cosmic Phys., 9, 14. Lucchin, F. "Introduzione alla cosmologia", 1998, Zanichelli, Bologna.5. Peebles, P.J.E., 1981, Astrophys. Journ., 248, 8856. Peebles, P.J.E., 1982, Astrophys. Journ., 258, 4157. Peebles, P.J.E. "The large-scale structure of the Universe", 1980, Princeton University Press, Princeton.8. Peebles P.J.E. 1993. Principles of Physical Cosmology. Princeton: Princeton Univ. Press 9. Padmanabhan, T. "Structure formation in the Universe", Cambridge Univ. Press, 1993.10. Sahni, V. & Coles, P., 1995. Approximation Methods for Nonlinear Gravitational Clustering, Phys. Rep., 262, 1
II. Statistica degli Aloni di Materia Oscura-Merging Trees
V. Confronto con Proprieta’ Osserv. delle Galassie
1. Vedi anche testi sez. IV2. Cimatti et al. 1999, Astron. Astrophys., 352, L453. Cimatti, A., et al. 2002, Astron. Astrophys., 392, 3954. Ellis, R. 1998, Nature, 395, 3 (supplement to No 6701, October 1, 1998)5. Fontana, A., et al 2003, Astrophys. Journ., 587, 5446. Fontana, A. et al., 2003, Astrophys. Journal, 594, L97. Ghigna et al. 2000, Astrophys. Journal., 544, 6168. Kauffmann, G., Charlot, S., 1998, Monthly Not. Roy. Astron. Soc,, 294, 7059. Kennicut, R.C., 1998, Astrophys. Journ., 498, 54110. Menci N. et al. 2003, astro-ph/031149611. Renzini, A., The formation of galactic bulges, edited by C.M. Carollo, H.C. Ferguson, R.F.G. Wyse. Cambridge, U.K. ; New York : Cambridge University Press, 1999. (Cambridge contemporary astrophysics), p.9 (astro-ph/9902108)12. Poli, F. et al., 2003, Astrophysical Journal Letters, 593, L113. Pozzetti, L. et al. 2003, Astron. Astrophys., 402, 83714. Steidel, C.C., Adelberger, K.L., Giavalisco, M., Dickinson, M., Pettini, M. 1999, Astrophys. Journ., 519, 1
VI. Evoluzione Cosmologica dei Nuclei Galattici Attivi
1. Di Matteo, T., et al. 2003, Astrophys. Journ., 593, 562. Ferrarese, L. Merritt, D., 2000, Astrophys. Journ., 539, L93. Gebhardt, K. et al., 2000, Astrophys. Journ., 539, L134. Kauffmann, G., Haehnelt, M., 2000, Monthly Not. Roy. Astron. Soc., 311, 5765. Menci, N. et al. 2003, Astrophys. Journ. 587, L636. Rees, M.J., 1984, ARAA, 22, 471
VII. Ammassi di Galassie
1. Sarazin, C., 1986, Rev. Mod. Phys., 58, 12. Cavaliere, A. et al. 1997, Astrophysical Journal, 484, L213. Cavaliere, A. et al. 1999, Monthly Not. Roy. Astron. Soc., 308, 5994. Menci, N., Cavaliere, A., 1999, Monthly Not. Roy. Astron. Soc., 311, 505. Ponman, T. J.; Cannon, D. B.; Navarro, J. F., 1999, Nature, 397, 135
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r
coldacc
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Cavaliere Vittorini 2000
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3/4 feeds circumnuclear starbursts
t
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QSO Properties Starbursts Properties
r
coldmftvm
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Pre-collision t ~ 0.01(rinit/h)3/2 trot
As the galaxies fall in towards each other for the first time, they move on simple parabolic orbits until they are close enough that they have entered each others' dark halos, and the gravitational force becomes non-Keplerian. During this infall, the galaxies hardly respond to one another at all, save for their orbital motion.
Impact t ~ 0.3 (rp/h)3/2 trot As the galaxies reach perigalacticon, they feel the strong tidal force from one another. The galaxies become strongly distorted, and the tidal tails are launched from their back sides. Strong shocks are driven in the galaxies' ISM due to tidal caustics in the disks as well as direct hydrodynamic compression of the colliding ISM.
Gravitational Response t ~trot
As the galaxies separate from their initial collision, the disk self-gravity canamplify the tidal distortions into a strong $m=2$ spiral or bar pattern. Thisself-gravitation response is strongly coupled to the internal structure of the galaxies as well as their orbital motion, resulting in a variety of dynamicalresponses
z=0.4
z=1
z=3
MBH~4
Cold gas mass ~ 2.5
Interactions favour large galact. masses 3.5
SN feedback disfavours small galact. masses 4
Data from Gebhardt et al. 2000 (circles)Ferrarese & Merrit 2000 (squares)
Menci et al. 04
Local Blue Galaxy Pop.u-r < 1.3
Local Red Galaxy Pop.u-r >1.8
-21< Mr < -19
log
MB
H (
Mʘ )
z=0.5z=2 z=1.2
z=4.2
z=3
Data from Hartwick & Shade 1990, Boyle et al 2000, Fan et al 2001
The normalization of the QSO LFs - increases from z=0 to z=2- decreases for z>2
The shape of the QSO LFsprogressively flattens for z>2.5
The rise with z of the normalization is due to the increasing fraction of destabilized cold gas feeding the BH
The encounter rate and the hence the accretion rate increases with z
BECAUSE
The flattening is due to the rapid exaustion of galactic cold gas in larger galaxies, whose star formation is peaked at higher z
Data from Hartwick & Shade 1990, Warren, Hewitt, Osmer 1994, Goldschmidt & Miller 1998, Boyle et al 2000, Fan et al 2001
The rapid decrease at z<2.5 is due to 3 concurring factors
1) The decrease with time of the merging rate of galaxies
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 cold gas funneling toward the nucleus
Previous works adopting SAMstreated the accreted fraction fas a free parameter constant with z(missed process #3)
Cold Gas destabilization from Fly-by interactions strongly decreases from z=3 to z=0
At high z a large amount of cold gas is destabilized
Strong starbursts are expected at z > 3-4
Data from Steidel et al. 99
The effect of Starbursts on the Galaxy Lum. Function.
NM et al. 2004
The effect of Starbursts induced by fly-by events in the K-band observables
K-band Lumin. Functions
K-band z-counts
NM et al 2004
Data from Fontana et al. 03
The stellar Mass Function (Fontana et al. 04)
M=1013 M⊙
M=1012 M⊙
M=2.5 1011 M⊙
M=5 1010 M⊙
Evolutinary Tracks Galaxies with DM mass of:
At z > 2.5 - 3rapid merging, frequent encounters allow
continuous refueling of gas in the growing galactic haloes.
Frequent encounters continuously destabilize an appreciable fraction of such a gas triggering:
- fast BH accretion: QSO at full Eddington rate - powerful starbursts
Such processes are produced preferentially in massive haloes due to their larger cross section for interactions.
At z < 2.5 - 3 i) Construction of galaxies and merging rate
declineii) 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)
- QSO only occasionally refueled by encounters- Emission drops down to L~ 10-2 LEddington
