1. P. Saracco 1 M. Longhetti 1, A. Gargiulo 1 1 INAF – Osservatorio Astronomico di Brera, Milano Italy Galaxy Evolution and Environment - Bologna, November 2009

2.  Introduction: first evidence of compact ETGs at z>1  A study of a sample of 65 ETGs at 0.9<z spec <2  Scaling relations of ETGs at z>1  Color gradients in high-z ETGs (an ongoing work)  Key observing follow-up  Conclusions and the key open question Galaxy Evolution and Environment - Bologna, November 2009

3. Daddi et al. (2005) Compact ETGs at z>1: first evidence Trujillo et al. (2006) 10 ETGs z>1.2 Near-IR ground based observations FWHM~1.0 arcsec Mass Re [Kpc] HST-ACS - F850W, λ rest <3000 Ǻ Hubble UDF - 7 ETGs z>1.4 Galaxy Evolution and Environment - Bologna, November 2009

4. Expected KR at z=1.5 passive luminosity evolution (maximum evolution expected for early-types). Observed KR at z=0. Expected locus for z<1.5 early-type galaxies in case of luminosity evolution. The SB exceeds by ~1 mag the one expected in the case of PLE for constant R e, i.e. luminosity evolution does not account for the observed SB of ETGs at high-z. (Longhetti, Saracco, et al. 2007) HST-NICMOS (0.075”/pix) observations of 10 ETGs at 1.2<z spec <1.5 Kormendy relation in the R band Galaxy Evolution and Environment - Bologna, November 2009

5. Many independent confirmations Trujillo et al. (2007) Based on small sample (≤10 ETGs) and/or on photometric z. Cimatti et al. (2008) Damjanov et al. (2008) van Dokkum et al. (2008) McGrath et al. (2008) Buitrago et al. (2008) etc. Galaxy Evolution and Environment - Bologna, November 2009 High-z ETGs are more compact than local ETGs

6. Large sample of z>1 ETGs needed Literature and HST archive research Aim – collecting a large (larger than 10…!) sample of ETGs at z>1 with spectroscopic confirmation of redshift and spectral type; HST observations (NICMOS and/or ACS) F160W or F850LP filter; multiwavelength coverage (optical + near-IR + mid-IR) 65 early-type galaxies 0.9<z spec <2 U,B,V,R,I,z,J,H,K,3.6,4.5,5.8,8.0 µm 30 ETGs 1<z<2, 17.0<K<20, HST-NICMOS observations F160W (Saracco et al. 2009) 10 ETGs 1.2<z<1.7 from TESIS (Saracco et al. 2005; Longhetti et al. 2005) 10 ETGs 1.4<z<1.9 from GDDS (Abraham et al. 2004; McCarthy et al. 2005) 6 ETGs z~1.27 from RDCS 0848+4453 (Stanford et al.1997; van Dokkum et al. 2003 3 ETGs 1<z<1.8 from HDF-N (Stanford et al. 2004) 1 ETGs z=1.55 53W091 (Dunlop et al. 1996; Waddington et al. 2002) 35 ETGs 1<z<2, 17.0<K<20, HST-ACS observations F850LP, F606W (GOODS-South) 9 ETGs 1.4<z<2 from GMASS (Cimatti et al. 2008) 12 ETGs 0.9<z<1.2 from van der Wel et al. (2005) and Rettura et al. (2006) 5 ETGs 0.9<z<1.2 from K20 (di Serego Alighieri et al. 2005) 9 New ETGs 0.9<z<1.9 from the GOODS-South survey Galaxy Evolution and Environment - Bologna, November 2009

7. Size-Mass (S-M) relation Compact ETGs 2.5-3 times smaller than local ETGs and than Normal ETGs Compact ETGs :15-30 times denser ! Galaxy Evolution and Environment - Bologna, November 2009 34 ETGs (~50%) are smaller than local ETGs with equal stellar mass. 31 ETGs (~50%) agree with the local S-M relation.

8. Size-Luminosity (S-L) relation Normal ETGs Compact ETGs Galaxy Evolution and Environment - Bologna, November 2009 follow the local S-L relation 2.5-3 times smaller than local ETGs

9. The Kormendy relation in the R-band z=0 z~1.5 The ETGs at z~1.5 are placed on the [ e,R e ] plane according to the KR. z~1.5 ETGs follow the KR at z=0 with a different zero-point. ~50% of the sample occupies the KR at z=0. ~50% does not match the local KR, their SB exceeds by 1-1.5 mag the one at z=0. Galaxy Evolution and Environment - Bologna, November 2009

10. Superdense and Normal ETGs coexist at 1<z<2 Normal ETGs They follow the local S-M relation. Luminosity evolution brings them onto the local Kormendy and S-L relations. No effective radius evolution required. Compact ETGs They do not follow the local scaling relations. They are 2.5-3 times smaller than their local and high-z counterparts with comparable mass, SB and luminosity. Effective radius evolution required. What does it make the difference ? Different assembly histories ? Galaxy Evolution and Environment - Bologna, November 2009

11. Normal Compact Compactness vs zCompactness vs z form R e : effective radius of the galaxy R e,z=0 : effective radius of a galaxy of equal mass at z=0 derived from the local S-M relation At high z only compact ETGs form. Galaxy Evolution and Environment - Bologna, November 2009

12. Normal Compact Stellar mass vs zStellar mass vs z form “downsizing” At high z only compact and high-mass ETGs form Galaxy Evolution and Environment - Bologna, November 2009

13. Normal and Compact ETGs: different assembly histories Normal ETGs: Low-z dry-merger products ? Last episode of star formation occurred at z form <2.5. Dissipation-less (gas poor) mergers of small sub-units at low z  efficient mechanism to produce large ETGs. (e.g. Boylan-Koclhin et al. 2006, ’08, Ciotti et al. 2007) Compact ETGs: High-z gas-rich merger/collapse products ? Last episode of star formation occurred at 2<z form <10. Gas-rich merger/collapse  high fraction of stars forms in situ through a violent starburst  highly compact and massive ETGs. (e.g. Khochfar et al. 2008; Naab et al. 2007, Ciotti et al. 2007 ) What does it rout ETGs in the different assembly histories ? Environment …? Galaxy Evolution and Environment - Bologna, November 2009

14. Tracing the evolution of Compact ETGs at z<2 They must increase their size by 2.5-3 times to match the local scaling relations. Dissipation-less “dry” merging: the size increases according to the relation Boylan-Kolchin et al. 2006-08 Khochfar and Silk 2006 Nipoti et al. 2002, 2009 Ciotti et al. 2007 Too many high-mass ETGs Galaxy Evolution and Environment - Bologna, November 2009

15. Tracing the evolution of Compact ETGs at z<2 They must increase their size by 2.5-3 times to match the local scaling relations. Dissipation-less “dry” merging: the size increases according to the relation Boylan-Kolchin et al. 2006-08 Khochfar and Silk 2006 Nipoti et al. 2002, 2009 Ciotti et al. 2007 Too many high-mass ETGs Galaxy Evolution and Environment - Bologna, November 2009 Are compact ETGs the progenitors of the BCGs ?

16. Surface brightness profiles: obs vs fitting Galaxy Evolution and Environment - Bologna, November 2009 F850LPF606W FWHM~0.1”

17. Color gradients in ETGs at z>1 Galaxy Evolution and Environment - Bologna, November 2009 FWHM~0.1” Simulations to check for each galaxy  the reliability of the measured gradient;  the uncertainty and the significance of the measured gradient. Are color gradients mainly present in Normal or in Superdense ETGs ?

18. 1. Compact vs Normal ETGs: two formation scenarios ? Near-IR/optical color gradients: HST high resolution (≤0.1”) near-IR and optical imaging. Key observations 2. Were compact ETGs really denser in the past ? Spectroscopic observations to measure the velocity dispersion: at fixed mass the smaller the size, the higher the density and, consequently, the velocity dispersion. Awaiting for the ESO-OPC (P85) and LBT TACs’ verdict. Galaxy Evolution and Environment - Bologna, November 2009 VLT ISAAC Saracco et al. 2005; Longhetti et al. 2005) σ v =410±…km/s

19. Normal and superdense ETGs coexist at z>1. Their different physical properties imply that they follow two distinct formation and evolutionary paths. Galaxy Evolution and Environment - Bologna, November 2009 Thank you ! Has the environment the X-Factor ?

20. Best-fitting template to the observed SED at z spec Charlot & Bruzual ’08 models: IMF: Chabrier 0≤Av≤0.6 mag SFH: 0.1, 0.3, 0.4, 0.6 Gyr Z=0.2 Z סּ, Z סּ, 2 Z סּ Best fitting values: Av<0.4 mag (85%) SFH< 0.3 Gyr (90%) Z=Z סּ (90%) Galaxy Evolution and Environment - Bologna, November 2009

21. Best-fitting template to the observed SED at z spec Charlot & Bruzual ’08 models: IMF: Chabrier 0≤Av≤0.6 mag SFH: 0.1, 0.3, 0.4, 0.6 Gyr Z=0.2 Z סּ, Z סּ, 2 Z סּ Best fitting values: Av<0.4 mag (85%) SFH< 0.3 Gyr (90%) Z=Z סּ (90%) Galaxy Evolution and Environment - Bologna, November 2009

22. Effective radius r e (arcsec) and mean surface brightness (SB) e within r e from Sersic profile fitting n=4 de Vaucouleurs profile n=1 exponential profile galfit (Peng et al. 2002) to perform the fitting after the convolution with the NIC2 PSFs. 0.075 “/pixel NIC2 images models residuals z=1.34 z=1.40 z=1.7 n=3.2 n=4.5 n=2.7 HST-NICMOS observations of 10 ETGs at 1.2<z<1.7. (Longhetti et al. 2007) Data sampling the rest-frame R-band (λ rest ~6500 Ǻ) at z~1.4, at a spatial resolution <0.8 kpc (FWHM~0.12 “) Galaxy Evolution and Environment - Bologna, November 2009

23. Av vs Age Galaxy Evolution and Environment - Bologna, November 2009

24. Re(F850LP) vs Re(F606W) Galaxy Evolution and Environment - Bologna, November 2009

25. The Kormendy relation in the R-band z=0 z~1.5 The ETGs at z~1.5 are placed on the [ e,R e ] plane according to the KR. z~1.5 ETGs follow the KR at z=0 with a different zero-point. ~50% of the sample occupies the KR at z=0. ~50% does not match the local KR, their SB exceeds by 1-1.5 mag the one at z=0. Galaxy Evolution and Environment - Bologna, November 2009

26. Compactness vs stellar mass 5% Stellar mass Galaxy Evolution and Environment - Bologna, November 2009

27. Mean age vs stellar mass 5% Stellar mass Galaxy Evolution and Environment - Bologna, November 2009

28. Mass density vs vs stellar mass 5% Stellar mass Galaxy Evolution and Environment - Bologna, November 2009

29. The evolution of the zero point α Zero point α of the KR derived from various samples at different redshifts. The curves show the expected evolution of α for different formation redshift zf. Luminosity evolution + Evolution of R e Our sample Luminosity evolution SFH tau=0.6 Gyr, solar metallicity, Chabrier IMF Longhetti et al. 2007 Galaxy Evolution and Environment - Bologna, November 2009

30. Luminosity evolution of Young and Old ETGs Saracco et al. 2008 Galaxy Evolution and Environment - Bologna, November 2009

31. 100 simulated galaxies magnitudes F160W and r e assigned randomly in the ranges 19<F160W<21 and 0.1< r e <0.5 arcsec (1-5 Kpc at z~1.4); axial ratio b/a and position angle PA in the ranges 0.4<b/a<1 and 0<PA<180 Simulations Real galaxies Simulated De Vaucouleurs profile To assess the robustness of the results we applied the same fitting procedure to a set of simulated galaxies Galaxy Evolution and Environment - Bologna, November 2009

32. Absolute magnitudes Galaxy Evolution and Environment - Bologna, November 2009

33. Size-Luminosity/Mass relations SDSS Shen et al. (2003) Size-LuminositySize- Mass Galaxy Evolution and Environment - Bologna, November 2009