Hot topics on Galaxy Formation and Evolution 3. Archeology and Size - - PowerPoint PPT Presentation

Padova, March 2012 Hot topics on galaxy formation and evolution 3 Page 1

Hot topics on Galaxy Formation and Evolution

• 3. Archeology and Size Evolution

Roberto Saglia Max-Planck Institut für extraterrestrische Physik Garching, Germany

Padova, March 2012 Hot topics on galaxy formation and evolution 3 Page 2

Outline

• Constraints on formation epochs of local early-type galaxies:

galaxy archeology

• Constraints from redshift evolution
• Size evolution of galaxies
• Constraints on the IMF

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Ages and metallicities

Lick indices , , to break the age-metallicity degeneracy

b

Mg Fe Hβ < > Trager et al. 2000 AJ, 120, 165

[ ]

/ log( / ) log( / ) Z H Z H Z H = −

e

0.02 Z =

e

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Galaxy archeology

Thomas et al. 2005, ApJ, 621, 673 Red: Es, Blue:S0, Green: cD

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Element abundances in solar neighbourhood: see: Wheeler et al. ARAA 27 (1989)

, ,

/ [ / ] log /

α α

ρ ρ α ρ ρ =

e e Fe Fe

Fe

[α/O] = logarithm of the ratio of density of alpha elements (Mg, Si, Ca, Ti) and density of Fe relative to this ratio in the sun:

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Mg/Fe

• verabundance

Enrichment through Supernovae of Type II Only short (<1Gyr) time scales for the star formation are allowed. Type I SNs produce Fe to solar values Hierarchical galaxy formation problematic?

elements(O, Mg, Ca...) enhanced with respect to Fe α −

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The epoch and duration of formation of Es

Big (local) ellipticals formed their stars early and quickly. Small ellipticals formed their stars more recently and with more extended periods of star formation. Formation in low density environments happens with some delay.

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The formation epoch of dark halos

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The Fundamental Plane of Elliptical Galaxies

A comprehensive set of global parameters of elliptical galaxies is: The half light (or effective) radius re The mean surface brightness Ie (or Σe) within re The central velocity dispersion σ0 The luminosity L The mass M The following two relations relate these quantities: with the structure parameter c which contains all unknown details about the galaxies’ structure.

e 2 2

/ 2 (Definition of mean surface brightness within r ) (Virial equilibrium)

e e e

L r M c r π σ Σ = =

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Multiplication yields an expected relation for these parameters: Because neither M/L or c are expected to vary very much, the brackets are nearly constant and imply that ellipticals should define a plane-like distribution in the 3-space of their global parameters (re, Σe, σ0

2).

Astonishingly, this plane is much better defined than naively expected, with very low dispersion perpendicular to the plane (implying a variance in the product of the brackets less than 10%) and a small but significant tilt (implying small but significant changes in the structure of ellipticals as a function of their luminosity or mass), see Djorgovski & Davis 1987, Dressler et al. 1987. The observed so-called ”fundamental plane” relation reads: This is consistent with the virial expectation, if

1 2 1

2

e e

c M r L σ π

− −

⎛ ⎞⎛ ⎞ = Σ ⎜ ⎟⎜ ⎟ ⎝ ⎠⎝ ⎠

1.4 0.85 0.2 0.25

2

e e

r M M L c L σ π

−

∝ Σ ⎛ ⎞⎛ ⎞ ∝ ∝ ⎜ ⎟⎜ ⎟ ⎝ ⎠⎝ ⎠

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Ellipticals and bulges lie in a ‘fundamental plane’ è at a given mass, their M/L shows only <15% scatter è they have homogenous, mostly old stellar populations

Dressler et al. 1987, Djorgovski & Davis 1987, Bender, Burstein & Faber 1992,1994

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Giant ellipticals are described by the de Vaucouleurs profile: More generalized profile:

( )

1 4 e

7.67 r r

I(r) I(0) e

−

=

Sersic profiles

There exists a puzzling correlation

• f Sersic n with galaxy luminosity.

( )

1 n n e

b r r

I(r) I(0) e

−

=

Kormendy et al. 2009, ApJSS, 182, 216-209

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Bulge+Disk fits

• Fit 2-dimensional image

using GIM2D or GALFIT

• Use Sersic profiles or

Exponential+De Vaucouleurs (disk+bulge) profiles Simard et al. 2011, ApJSS, 196, 11 1.12 millions SDSS galaxies

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How to compute galaxy sizes

= + =

1/ 2

( )/ 2 ( )

ave e e har e e

R a b R a b

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P.I. S. White ( MPA-Garching, D )

• A. Aragón-Salamanca ( Nottingham, UK )
• R. Bender ( Munich, D )
• P. Best ( ROE, Scotland )
• M. Bremer ( Bristol, UK )
• S. Charlot ( MPA, D & IAP, F )
• D. Clowe ( Bonn, D)
• J. Dalcanton ( U.Washington, USA )
• B. Fort ( IAP, F )
• P. Jablonka ( OPM, F )
• G. Kauffmann ( MPA, D )
• Y. Mellier ( IAP, F )
• R. Pello ( OMP, F )
• B. Poggianti ( Padova, I )
• H. Rottgering ( Leiden, NL )
• P. Schneider ( Bonn, D )
• D. Zaritsky ( U. Arizona, USA )
• M. Dantel ( OPM, F )
• G. De Lucia ( MPA, D )
• V. Desai ( U. Washington, USA )
• C. Halliday ( Padova, I )
• B. Milvang-Jensen ( MPE, D )
• S. Poirier ( OPM, F )
• G. Rudnick ( MPA, D )
• R. Saglia (MPE, D )
• L. Simard ( U. Victoria, C )
• J. Varela ( Padova, I)

The ESO Distant Cluster Survey

(EDisCS) Study evolution of cluster galaxies and clusters in 20 fields with clusters at z=0.4 – 1.0

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THE DATASET

• Deep imaging: VRIJK at z~0.8, BVIK at z~0.5

(FORS2/VLT + SOFI/NTT) (White et al. 2005)

• HST/ACS imaging for 10 most distant clusters (80
• rbits, Desai et al. 2007). Re from GIM2D
• WFI/2.2m RVI imaging for all 20 fields
• XMM data for >=3 clusters (Johnson et al. 2006)
• Spectroscopy: at least 4 FORS2 masks/cluster at

long exposure to get spectra to I~23 (z~0.8) or 22 (z~0.5) (Halliday et al. 2004, Milvang-Jensen et al. 2008). s measured using pPXF for spectroscopic

early-type

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The EDISCS FP with HST

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M/L Evolution is 'passive'

Z(formation)=2 Salpeter IMF, solar metallicity

log / 2 5 M L ZP β Δ = Δ

Z(formation)=3.5 Salpeter IMF, half solar metallicity Z(formation)=1.5 Salpeter IMF, Twice Solar metallicity Field Galaxies have a lower Z formation

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Mass evolution

Lower-mass ellipticals evolve quicker Lower formation redshift ... but selection effects are nasty.

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Constraints on the IMF

Renzini 2005, Ap.Sp.Sci. 327,221 At z~0 the light of 12 Gyr stars is dominated by solar mass stars, at z~1.4 by stars 1.4 times more massive. A flatter IMF evolves faster than Salpeter The formation redshift has to be higher to match the data b b

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The cosmic evolution and the IMF

Van Dokkum 2008, ApJ, 674, 29 A flat-top IMF has a large number of short-lived starsàmore rapid luminosity evolution. A flat-top IMF reduces the number of turn-off stars with respect to more luminous red giants àweaker color evolution

Combination of color and FP Evolution can constrain the IMF

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The joint evolution of the FP and color

vD08 Zero-point evolution of the color-magnitude and FP relation for 8 clusters up to z=0.8àFlat-top IMF preferred. x=2.35 x~1

11

/ , too strong / too weak, OK best fit Elliptical galaxies 2, 2.3 wi 6, 2.35 th M 1 5: 1 : 4, :

f form r

• fo m

rm

M L OK U V M L U V M z z z α α α = = = Δ Δ − = ≥ ≈ Δ Δ − ≈

e

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Chabrier IMF

a~1 globally: too large M/L àthe test probes a only near 1 solar mass

1 2 2 1

0.14(0.5 25 ) exp (log log ) / 2 if 25 0.158 if 25 , 0.69

c c c c

m m m m m m m m

α α

ξ σ σ

− −

⎡ ⎤ = × − − ≤ ⎣ ⎦ = > =

... but a proper investigation taking into account IMF and size evolution is still missing

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The discovery of size evolution

Trujillo et al. 2006, ApJ 650, 18-41 SDSS Local galaxies

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The Mass-Size relation

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The size-z relation

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...and s evolution

Cenarro & Trujillo, 2009, ApJL, 696, 43 Puffing-up scenario Mergers

2

If decreases with redshift at constant ~ , than has to increase with redshift

e e

R M R σ σ

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Galaxies might puff up as a consequence of QSO activity

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Models: puffing-up

Fan et al. 2008, ApJ, 689, L101: quasar activity (plus supernovae) expels the gas from galaxies rapidly, that react expanding:

2 ' ' ' 2 ' ' '2 ' ' ' ' f ' 2 ' '

~ / , ~ ( / ) (2 / ) If / 2 the system can relax to a new equilibrium with E ~ / / 2 / increases and ~ / decreases E M R M M M E E M M M M M M M R E R R M M R M R δ σ − = − − − < − = → = − →

End of quasar phase Present day Local galaxies Problems: s does not increases to quickly with z, and R evolves also at z<1...

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Galaxies grow in size due to mergers

Movie Movie

1:1 merger 3:1 merger Thorsten Naab, MPA

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Cosmological simulations

Thorsten Naab, MPA

Stars

Blue: age < 1Gyr Yellow: 1Gyr < age < 5 Gyrs Orange: age > 5 Gyrs

Gas

Red: T >106 K Yellow: 104< T <106 K Blue: T < 104 K

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Models: mergers

( ) ( ) ( ) ( ) ( )

2 2 2 2 2 2 2 2 2 2 2 2 2 3 3 5

1 2 2 / ; / 1 1 (1 ) 2 2 1 1 / 1 1 / 1 1 / 1

i i i i i a i a i f i a i i f f f i f i f f i i f i f i f i f i f i i f

GM E M r M M E E E M M M M M M E r r E M M M r M r σ η ε σ σ σ εη σ η εη σ σ η η σ σ εη εη ρ ρ η = − = − = = = + = − + = − = + + = + + = = = + ⎛ ⎞ + = = ⎜ ⎟ ⎜ ⎟ + ⎝ ⎠

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Models: mergers

( ) ( ) ( ) ( ) ( )

2 2 2 2 2 2 2 2 2 2 2 2 2 3 3 5

1 2 2 / ; / 1 1 (1 ) 2 2 1 1 / 1 1 / 1 1 / 1

i i i i i a i a i f i a i i f f f i f i f f i i f i f i f i f i f i i f

GM E M r M M E E E M M M M M M E r r E M M M r M r σ η ε σ σ σ εη σ η εη σ σ η η σ σ εη εη ρ ρ η = − = − = = = + = − + = − = + + = + + = = = + ⎛ ⎞ + = = ⎜ ⎟ ⎜ ⎟ + ⎝ ⎠

Naab et al. 2009, ApJL, 699, L178

mergers : 1, 1 / 2, / 1, / 1/ 4 minor size evolution, no evolution Many mergers : 1, / 4, / 1/ 2, / 1/32 strong size evolution, mild evolution

f i f i f i f i f i f i

Major r r Minor r r η ε σ σ ρ ρ σ η ε σ σ ρ ρ σ = = = = = → = = = = = →

Simulated galaxy

11

1.5 10 M M

∗ =

×

e

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Luminosity profiles

Szomoru & van Dokkum 2012 ApJ, in press Simulated galaxy, Naab et al.

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The progenitor bias

Valentinuzzi et al. 2011, ApJ, 712, 226 The black dots show the Re

• f the local

(WINGS) early-types that stopped their star-formation 1.5Gyr before the redshift they are plotted at. Weak or NO SIZE evolution after all?

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Size evolution

2

5 /

dyn e

M R G σ =

Re = Rc(M / 2 ×1011M )0.56

1

,no progenitor bias (0)(1 )

c c

HST R R z − = +

0.5

, progenitor bias (0)(1 )

c c

HST with R R z − = +

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s evolution

11 0.23

( / 2 10 )

e c M

M σ σ = ×

e

0.59

progenitor bias (0)(1 )

c c

Without z σ σ = +

0.41

progenitor bias (0)(1 )

c c

With z σ σ = +

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Consequences for the FP evolution

2

2.5log 2

e

e

L SB R π < >= − log log ; log log

e e

e e

R SB ZP ZP R SB α σ β α σ β = + < > + = − − < > log log ( ) log (0) 10 1 2 2 = log log 5 5 5

e

L L z L ZP R β α σ β β β Δ = − = − Δ Δ + Δ −

log(1 ); log log(1 ); log log(1 )

e

ZP z R z z γ µ σ ν Δ = + Δ = + Δ = +

1/2

: , constant

e dyn

Puffing scenario R M σ

−

∝

0.5 0.1

: (1 ) , (1 )

e

Merger scenario R z z σ

−

∝ + ∝ +

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Luminosity evolution

10 1 2 2 log log(1 ) 5 5 5 L z β α µ ν γ β β β τ ⎡ ⎤ − Δ = + − + ⎢ ⎥ ⎣ ⎦ Δ →

HST, uniform weighting, with correction for Progenitor bias From FP with From fit

(0)(1 ) L L z λ = +

FP evolution

Δτ = 0

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Conclusions

• Galaxy 'archeology' of local Es points to old populations. Their halos formed

before their stars.

• Galaxies evolve with time in their stellar populations and structural properties
• Sizes of massive early-type galaxies were smaller in the past, velocity

dispersions were higher, but be aware of 'progenitor biases'.

• (Minor) mergers are the driving force of this evolution
• The Fundamental Plane evolution points to high formation redshifts for massive
• Es. A proper interpretation needs to take into account of size evolution.
• The combined analysis of the FP and color evolution has the potentiality to

probe the IMF

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EDisCS References

De Lucia et al. 2004, ApJL, 610, L77 Color-Magnitude, 2007, MNRAS, 374, 809 Halliday et al. 2004, A&A, 427, 397, spectroscopic White et al. 2005, A&A, 444, 365: Project description Finn et al. 2005, ApJ, 630, 238: Ha imaging Poggianti et al. 2006, ApJ, 642, 188: Star-Forming Fraction Clowe et al. 2006, A&A, 451, 395: Weak lensing analysis Johnson et al. 2006, MNRAS, 371, 1777, X-ray Desai et al. 2007, ApJ, 661, 1151, HST morphology Milvang-Jensen et al. 2008, A&A, 482, 419, final spectroscopy Whiley et al. 2008, MNRAS, 387, 1253 Brightest cluster galaxies Poggianti et al. 2008, ApJ, 684, 888, SF, morphology and density Poggianti et al. 2009, ApJ, 693, 112, Post starburst galaxies Barazza et al. 2009, A&A 497, 713, barred galaxies Sanchez-Blazquez, 2009, A&A, 499, 47, line indices Pello et al., 2009, A&A, 508, 1173, PhotoZ Simard et al. 2009, A&A, 508, 1141, GIM2D morphology Rudnick et al. 2009, ApJ, 700, 1559, Red LF Valentinuzzi et al. 2010, ApJ, 721, L19, size evolution Saglia et al. 2010, A&A, 524, A6, FP Jaffe' et al. 2011, MNRAS, 410, 280, Color-mag Jaffe' et al. 2011, MNRAS, 417, 1996, Tully-Fisher