P. Saracco 1 M. Longhetti 1, A. Gargiulo 1 1 INAF – Osservatorio Astronomico di Brera, Milano...

P. Saracco1M. Longhetti1, A. Gargiulo1 1 INAF – Osservatorio Astronomico di Brera, Milano Italy

Galaxy Evolution and Environment - Bologna, November 2009

Introduction: first evidence of compact ETGs at z>1 A study of a sample of 65 ETGs at 0.9<zspec<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


Daddi et al. (2005)Compact ETGs at z>1: first evidenceCompact ETGs at z>1: first evidence

Trujillo et al. (2006)

10 ETGs z>1.2Near-IR ground based observationsFWHM~1.0 arcsec

Mass

Re

[Kpc

]HST-ACS - F850W, λrest<3000 Ǻ

Hubble UDF - 7 ETGs z>1.4


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 The SB exceeds by by ~1~1 mag the mag the one expected in one expected in the case of PLE the case of PLE for constant for constant RRee, i.e. , i.e. luminosity luminosity evolution does evolution does not account for not account for the observed the observed SB of ETGs at SB of ETGs at high-zhigh-z. .

(Longhetti, Saracco, et al. 2007)HST-NICMOS (0.075”/pix) HST-NICMOS (0.075”/pix) observations of 10 ETGs at observations of 10 ETGs at 1.2<z1.2<zspecspec<1.5<1.5Kormendy relation in the R band


Many independent confirmationsMany 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.


High-z ETGs are more compact than High-z ETGs are more compact than local ETGslocal ETGs

Large sample of z>1 ETGs needed 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<zspec<2U,B,V,R,I,z,J,H,K,3.6,4.5,5.8,8.0 µm30 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

Size-Mass (S-M) Size-Mass (S-M) relationrelation

Compact ETGs 2.5-3 times smaller than local ETGs and than Normal ETGs Compact ETGs :15-30 times denser !

56.0

*51047.3][

M

MkpcRe


34 ETGs (~50%) are smaller than local ETGs with equal stellar mass.31 ETGs (~50%) agree with the local S-M relation.

Size-Luminosity (S-L) Size-Luminosity (S-L) relationrelation Normal ETGs

Compact ETGs


follow the local S-L relation2.5-3 times smaller than local ETGs

The Kormendy relation in the R-The Kormendy relation in the R-band band )log(92.22.18 e

Re R

)log(72.28.15 5.02.0

1.02.0 e

Re R

z=0z~1.5The ETGs at z~1.5 are placed on the [<µ>e,Re] 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.


Superdense Superdense andand Normal ETGs coexist at Normal ETGs coexist at 1<z<2 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 ?


Compactness vs zCompactness vs zform

Re: effective radius of the galaxyRe,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

Stellar mass vs zStellar mass vs zform

“downsizing”At high z only compact and high-mass ETGs formGalaxy Evolution and Environment - Bologna, November 2009

Normal and Compact ETGs: different Normal and Compact ETGs: different assembly historiesassembly histories • Normal ETGs: Low-z dry-merger products ? Last episode of star formation occurred at zform<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<zform<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

Tracing the evolution of Compact ETGs at z<2They 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

*MRe 3.16.0 Boylan-Kolchin et al. 2006-08Khochfar and Silk 2006Nipoti et al. 2002, 2009Ciotti et al. 2007

if RR 5.2 if MM 5.2 if MM /15.2

56.0

*61088.2][

M

MkpcRe

3.1if MM 1.2Too many high-mass ETGsGalaxy Evolution and Environment - Bologna, November 2009

Tracing the evolution of Compact ETGs at z<2They 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

*MRe 3.16.0 Boylan-Kolchin et al. 2006-08Khochfar and Silk 2006Nipoti et al. 2002, 2009Ciotti et al. 2007

if RR 5.2 if MM 5.2 if MM /15.2

3.1if MM 1.2Too many high-mass ETGsGalaxy Evolution and Environment - Bologna, November 2009

Are compact ETGs the progenitors of the BCGs ?

2009) al.et (Nipoti1.007.0

* cost MV

Surface brightness profiles: obs vs fitting


F850LP F606W

FWHM~0.1”

Color gradients in ETGs at z>1


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 ?

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

VLTISAAC

Saracco et al. 2005; Longhetti et al. 2005)σv=410±…km/s

Normal and superdense ETGs coexist at z>1. Their different physical properties imply that they follow two distinct formation and evolutionary paths.


Thank you !

Has the environment the X-Factor ?

Best-fitting template to the observed SED Best-fitting template to the observed SED at zat zspecspec Charlot & Bruzual ’08 models:IMF: Chabrier0≤Av≤0.6 magSFH: 0.1, 0.3, 0.4, 0.6 GyrZ=0.2 Zּס, Z 2, ּס Zּס

Best fitting values:Av<0.4 mag (85%)SFH< 0.3 Gyr (90%)Z=Z Galaxy Evolution and Environment - Bologna, November 2009)90%( ּס

sunel MmbM /mod

**

• Effective radius re (arcsec) and mean surface brightness (SB) <>e within re from Sersic profile fitting

n=4 de Vaucouleurs profilen=1 exponential profile

• galfit (Peng et al. 2002) to perform the fitting after the convolution with the NIC2 PSFs.

]1)/[( /1

)( n

en rrbeeIrI

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 HST-NICMOS observations of 10 ETGs at 1.2<z<1.71.2<z<1.7..

(Longhetti et al. 2007)(Longhetti et al. 2007)

Data sampling the rest-frame R-band (λrest~6500 Ǻ) at z~1.4, at a spatial resolution <0.8 kpc (FWHM~0.12 “)


Av vs Age


Re(F850LP) vs Re(F606W)


The Kormendy relation in the R-The Kormendy relation in the R-band band )log(92.22.18 e

Re R

)log(72.28.15 5.02.0

1.02.0 e

Re R

z=0z~1.5The ETGs at z~1.5 are placed on the [<µ>e,Re] 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.


Compactness vs stellar mass5% Stellar mass


Mean age vs stellar mass5% Stellar mass


Mass density vs vs stellar mass5% Stellar mass


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 Re

Our sample

Luminosity evolution

SFH tau=0.6 Gyr, solar metallicity,

Chabrier IMF

1)5.0()0()( zzRzR eeLonghetti et al. 2007

)log( ee R


Luminosity evolution of Young and Old ETGs

templategalgal

WFRLR

tAgeRAgeRzE

zEkzDWFzM

)]()([)(

)()(log5160)( 160,

Saracco et al. 2008Galaxy Evolution and Environment - Bologna, November 2009

100 simulated galaxies

• magnitudes F160W and re assigned randomly in the ranges 19<F160W<21 and 0.1< re <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


Absolute magnitudes

templatezzWFR

WFRgalLR

galWFRk

kzDWFM

)160(

)](log[5160

0160,

160,


Size-Luminosity/Mass relations

SDSS Shen et al. (2003)Size-Luminosity Size- Mass

02.526.0][log Re MkpcR56.0

*51047.3][

M

MkpcRe

02.526.0][log Re MkpcRGalaxy Evolution and Environment - Bologna, November 2009

P. Saracco 1 M. Longhetti 1, A. Gargiulo 1 1 INAF – Osservatorio Astronomico di Brera, Milano...

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