Hot topics on Galaxy Formation and Evolution. 3. Archeology and Size Evolution

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1 Page 1 Hot topics on Galaxy Formation and Evolution 3. Archeology and Size Evolution Roberto Saglia Max-Planck Institut für extraterrestrische Physik Garching, Germany

2 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

3 Ages and metallicities [ ] Page 3 Lick indices Mg, < Fe >, H β to break the age-metallicity degeneracy = Z = 0.02 e Z/ H log( Z/ H) log( Z/ H) b e Trager et al AJ, 120, 165

4 Galaxy archeology Thomas et al. 2005, ApJ, 621, 673 Page 4 Red: Es, Blue:S0, Green: cd

5 Page 5 Element abundances in solar neighbourhood: [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: ρα / ρ [ α / Fe] = log ρ / ρ Fe α, e Fe, e see: Wheeler et al. ARAA 27 (1989)

6 Mg/Fe overabundance Enrichment through Supernovae of Type II Page 6 α elements(o, Mg, Ca...) enhanced with respect to Fe Only short (<1Gyr) time scales for the star formation are allowed. Type I SNs produce Fe to solar values Hierarchical galaxy formation problematic?

7 The epoch and duration of Page 7 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.

8 Page 8 The formation epoch of dark halos

9 The Fundamental Plane of Elliptical Galaxies A comprehensive set of global parameters of elliptical galaxies is: Page 9 " The half light (or effective) radius r e " The mean surface brightness I e (or Σ e ) within r e " The central velocity dispersion σ 0 " The luminosity L " The mass M The following two relations relate these quantities: Σ = e L /2 (Definition of mean surface brightness within r e ) π r 2 e M r e = c σ 2 0 (Virial equilibrium) with the structure parameter c which contains all unknown details about the galaxies structure.

10 Multiplication yields an expected relation for these parameters: r e 1 c M = σ Σ 2π L e Page 10 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 (r e, Σ e, σ 02 ). 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 The observed so-called fundamental plane relation reads: This is consistent with the virial expectation, if r e σ 0 Σ e 2π M M L c L

11 Page 11 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

12 Sersic profiles Page 12 Giant ellipticals are described by the de Vaucouleurs profile: ( ) I(r) I(0) e 7.67 r r 14 e = More generalized profile: ( ) 1n n e I(r) = I(0) e b r r Kormendy et al. 2009, ApJSS, 182, There exists a puzzling correlation of Sersic n with galaxy luminosity.

13 Bulge+Disk fits Page 13 Fit 2-dimensional image using GIM2D or GALFIT Use Sersic profiles or Exponential+De Vaucouleurs (disk+bulge) profiles Simard et al. 2011, ApJSS, 196, millions SDSS galaxies

14 How to compute Page 14 galaxy sizes R = ( a + b )/2 R ave e e = ( a b ) har e e 1/ 2

15 The ESO Distant Cluster Survey Page 15 (EDisCS) Study evolution of cluster galaxies and clusters in 20 fields with clusters at z= 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 ) Padova, March 2012 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) Hot topics on galaxy formation and evolution 3

16 Page 16 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 orbits, 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

17 The EDISCS FP with HST Page 17

18 M/L Evolution is 'passive' Page 18 Δ log M / L = 2ΔZP 5β Z(formation)=2 Salpeter IMF, solar metallicity Z(formation)=3.5 Salpeter IMF, half solar metallicity Field Galaxies have a lower Z formation Z(formation)=1.5 Salpeter IMF, Twice Solar metallicity

19 Mass evolution Page 19 Lower-mass ellipticals evolve quicker Lower formation redshift... but selection effects are nasty.

20 Constraints on the IMF Page 20 b 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 Renzini 2005, Ap.Sp.Sci. 327,221

21 The cosmic evolution and the IMF Page 21 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 Van Dokkum 2008, ApJ, 674, 29 Combination of color and FP Evolution can constrain the IMF

22 Page 22 The joint evolution of the FP and color x=2.35 x~1 Zero-point evolution of the color-magnitude and FP relation for 8 clusters up to z=0.8à Flat-top IMF preferred. z z z form form form = 2, α = 2.35: ΔM / L OK, ΔU V too strong = 6, α = 2.35 : ΔM / L too weak, ΔU V OK 4, α 1: best fit Elliptical galaxies with M M e vd08

23 a~1 globally: too large M/L à the test probes a only near 1 solar mass Page 23 Chabrier IMF ξ = 1 α ( mc) exp (log m log mc) / 2 σ if m 25mc = > = 1 α m if m 25 mc, σ but a proper investigation taking into account IMF and size evolution is still missing

24 The discovery of size evolution Page 24 Trujillo et al. 2006, ApJ 650, SDSS Local galaxies

25 The Mass-Size relation Page 25

26 The size-z relation Page 26

27 ...and s evolution Page 27 If R decreases with redshift at constant M ~ Rσ, e than σ has to increase with redshift Puffing-up scenario e 2 0 Cenarro & Trujillo, 2009, ApJL, 696, 43 Mergers

28 Galaxies might puff up as a consequence of QSO activity Page 28

29 Models: Page 29 puffing-up Fan et al. 2008, ApJ, 689, L101: quasar activity (plus supernovae) expels the gas from galaxies rapidly, that react expanding: 2 ' E ~ M / R, M = M δ M ' ' 2 ' E ~ E( M / M) (2 M / M ) ' If M / M < 2 the system can relax to a new equilibrium with E ~ M / R = E R/ R = 2 M / M f '2 ' ' ' ' ' 2 ' ' R increases and σ ~ M / R decreases End of quasar phase Local galaxies Problems: s does not increases to quickly with z, and R evolves also at z<1... Present day

30 Page 30 Movie Galaxies grow in size due to mergers Movie 1:1 merger 3:1 merger Thorsten Naab, MPA

31 Cosmological simulations Page 31 Stars Blue: age < 1Gyr Yellow: 1Gyr < age < 5 Gyrs Orange: age > 5 Gyrs Thorsten Naab, MPA Gas Red: T >10 6 K Yellow: 10 4 < T <10 6 K Blue: T < 10 4 K

32 Models: mergers Page 32 E 2 i 2 i = = Miσ i 2ri a i a i 2 2 f i a i i f f 2 2 f i ( 1 η ) 1 η = M / M ; ε = σ / σ 1 1 E = E + E = Mσ (1 + εη) = M σ 2 2 M = + M σ r f f / σ / r i GM 1+ εη = 1 + η i E M M = = = E M M 2 2 i f σ i f 2 2 f i σ f i ( 1 εη) 5 ( 1 η ) 3 3 M f r + i ρf / ρi = = M i r f + 2 ( 1+ η ) ( 1+ εη )

33 Models: mergers E 2 i 2 i = = Miσ i 2ri a i a i 2 2 f i a i i f f 2 2 f i ( 1 η ) 1 η = M / M ; ε = σ / σ 1 1 E = E + E = Mσ (1 + εη) = M σ 2 2 M = + M σ r f f / σ / r i GM 1+ εη = 1 + η i E M M = = = E M M 2 2 i f σ i f 2 2 f i σ f i ( 1 εη) 5 ( 1 η ) 3 3 M f r + i ρf / ρi = = M i r f + 2 ( 1+ η ) ( 1+ εη ) Major mergers : η = 1, ε = 1 r / r = 2, σ / σ = 1, ρ / ρ = 1/4 f i f i f i Naab et al. 2009, ApJL, 699, L178 Page 33 minor size evolution, no σ evolution Many Minor mergers : η = 1, ε = 0 r / r = 4, σ / σ = 1/ 2, ρ / ρ = 1/ 32 f i f i f i strong size evolution, mild σ evolution Simulated galaxy 11 M = Me

34 Luminosity profiles Page 34 Szomoru & van Dokkum 2012 ApJ, in press Simulated galaxy, Naab et al.

35 The progenitor bias Page 35 The black dots show the Re of 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? Valentinuzzi et al. 2011, ApJ, 712, 226

36 M = R G dyn 2 5 eσ / Size evolution R e = R c (M / M ) R (0)(1 ) c = Rc + z Page 36 HST, no progenitor bias HST, with progenitor bias R (0)(1 ) c = Rc + z 0.5

37 s evolution Without progenitor bias σ (0)(1 ) c = σc + z 0.59 Page 37 σ = σ e c( M /2 10 M e ) With progenitor bias σ (0)(1 ) c = σc + z 0.41

38 Consequences for the FP Page 38 evolution log R = αlog σ + β < SB >+ ZP; ZP= log R αlogσ β< SB > e e L < SB >= 2.5log e 2 π R Δ log L= log L( z) log L(0) = 10β 1 2α 2ΔZP = Δ log Re + Δlogσ 5β 5β 5β Δ ZP = γ log(1 + z); Δ log R = µ log(1 + z); Δ logσ = νlog(1 + z) Puffing scenario R M e e 2 e 1/2 : σ e, dyn constant Merger scenario : R (1 + z), σ (1 + z) e e

39 Luminosity evolution 10β 1 2α 2 Page 39 Δ log L= µ + ν γ log(1 + z) 5β 5β 5β Δτ FP evolution HST, uniform weighting, with correction for Progenitor bias From FP with Δτ = 0 From fit L= L(0)(1 + z) λ

40 Page 40 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

41 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 EDisCS Page 41 References