A Wide Area Survey for High-Redshift Massive BzK Galaxies

X.Kong, M.Onodera, C.Ikuta (NAOJ), K.Ohta (Kyoto),N.Tamura (Durham), A.Renzini, E.Daddi, L. Da Costa (ESO),

A.Cimatti (Arcetri), T.Broadhurst (Tel’Aviv), L.F.Olsen (Cote d’Azur)

N. ARIMOTO (NAOJ)

Kong et al. (2006) ApJ 638, 72

EIS Deep 3a Survey

We have undertaken a fairly deep, wide-field imaging with the Subaru/Suprime-Cam of two fields of 900 arcmin2 each for part of which near-IR data are available from ESO

NTT observations.

EIS3a-F (Subaru/NTT, Ks=20.8) 320 arcmin2

Daddi-F (Subaru/NTT, Ks=19.0) 600 arcmin2

The prime aim of this survey is to understandhow and when the present-day massive

galaxies formed. To this end, the imaging observations have been optimized for the use of optical/near-infrared multi-colour selectioncriteria to identify both star forming (sBzKs)

and passive galaxies (pBzKs).

Kong et al. (2006) ApJ 638, 72

Subaru/Sup-Cam Observation

Daddi FieldRA=14:49:29, DEC=09:00:00 (J2000.0)

Subaru/Suprime-Cam BIz’: 2003/03/02-04WHT R : 1998/03/19-21NTT/SOFI K : 1999/03/27-30 BRIz’ (940 arcmin2) 3σ in 2”(AB) B(AB)=26.59 R(AB)=25.64 I(AB)=25.62 z’(AB)=25.31

K (600 arcmin2) 3σ in 2”(AB) Ks(AB)=20.91

940arcmin2

600arcmin2

Subaru/Sup-Cam Observation

ESO Imaging Survey (EIS Deep 3a) FieldRA=11:24:50, DEC=-21:42:00 (J2000.0)

Subaru/Suprime-Cam BRIz’: 2003/03/02-04NTT/SOFI JK : 2002/03/28-31 BRIz’ (940 arcmin2) 3σ in 2”(AB) B(AB)=27.46 R(AB)=26.87 I(AB)=26.56 z’(AB)=26.07

JK (320 arcmin2) 3σ in 2”(AB) J(AB)=23.40, Ks(AB)=22.70

940arcmin2

320arcmin2

High-z galaxies Deep 3a field

Star-forming galaxies at z>1.4 (sBzKs)

Old galaxies at z>1.4: (pBzKs)

stars

BzK=(z-K)-(B-z)>-0.2

（ｚ－K)>2.5

Daddi et al. (2004) ApJ 617, 746

SEDs of sBzKs and pBzKs

star-formingpassive

low-z

high-z

Photometric Redshift

Spectroscopic Redshifts (VLT)

Daddi et al. (2006)

pBzK(ERO) sBzK 　　 sBzK 　　 sBzK

ERO ERO 　　　 ERO 　　 ERO

Star/Galaxy Separation

(z-K)AB-0.3(B-z)AB<-0.5

387 sBzK 121 pBzK

108 sBzK 48 pBzK

513 ERO

337 EROs

Photometric Redshift (EROs)

Photometric Redshift (sBzKs)

Photometric Redshift (pBzKs)

Number Counts of sBzKs, pBzKs, and EROs

EROs

galaxies

sBzKs

pBzKs

Two Point Correlation Functions w(Θ)

Daddi-F Deep 3a-F

Landy & Szalay (1993)

Angular Clustering Amplitude

Physical Properties of sBzKs and pBzKs

• Supposing <z> ～ 2 for sBzKs, we have derived their physical properties, such as the reddening, star formation rate, and the stellar mass.

(While errors by a factor of 2 or more may affect individual estimates, the average quantities should be relatively robust.)

• Reddening : E(B-V)=0.25(B-z+0.1)AB ←UV Continuum slope (Calzetti law)

• SFR : SFR(Mo/yr)=L1500[erg/s/Hz]/8.85x1027

• Stellar Mass : log(M*/1011Mo)=-0.4(Ktot-20.14Vega)

The filled area is the histogram for sBzKs which associated with X-ray sources (25%).

The dashed lines are for the stellar mass histograms of pBzKs.

MAMBO & Spitzer (MIPS) Observations of sBzKs at z ～ 2

Dannerbauer et al. (2006) ApJ 637, L5 　 (Poster 14 　 Dannerbauer)

B B

z z

IR SFR ～ UV SFR

sBzKs

sBzKs(GOODS-N)Local

ULIRGs

SMGs

Contribution of sBzKs and pBzKs to Stellar Mass Density at z=2

25% AGN

Number density of pBzKswith M*>1011Mo over

the range 1.4<z<2.0(1.8±0.2)x10-4Mpc-3

Local value of massiveellipticals at z=0

9x10-4Mpc-3

(Baldry et al. 2004)

logρ*(total)=7.7 Mo/Mpc3

logρ*(total)=7.86 Mo/Mpc3

(1.5<z<2.0, Fontana et al 04)logρ*(total)=7.65 Mo/Mpc3

(2.0<z<2.5, Fontana et al 04)logρ*(total) ～ 7.5 Mo/Mpc3

(@z ～ 2, Dickinson et al 03)

20%±7% of massive (M*>1011Mo),passively evolving galaxies at z=0.

Summary (I) – Number Counts

BzK selection is a quite powerful way to separatehigh-z galaxies such as sBzKs, pBzKs and EROs

at 1.4<z<2.5.

1) Down to the K-band limit of the survey the log of the number counts of sBzKs increases linearly with the

K-magnitude, while that of both EROs and pBzKs flattens out by Kvega ～ 19.

EROs are in a modest redshift shell (z ～ 1), while pBzKs are also in a relatively narrow

redshift shell but at higher redshift (z ～ 1.5).sBzKs are drawn from a large range of redshifts,

and their relative numbers increase sharply with redshift.

Summary (II) - Clustering

2) The clustering properties of EROs and sBzKs arevery similar, clustering amplitudes ～ 10 times

higher than generic galaxies in the same magnitude range.

This suggests an evolutionary link between sBzKsat z ～ 2 and EROs at z ～ 1, with star formation

on sBzKs quenching by z ～ 1 thus producing passively evolving EROs.

The clustering amplitude of pBzKs is even higherthan that of sBzKs and EROs, suggesting that quenching epoch of star formation in massive

galaxies depends on environmental density.

Summary (III) – Physical Properties

3) sBzK galaxies (KVega<20) have median reddeningE(B-V) ～ 0.40, average SFR ～ 190 Mo/yr,

typical stellar mass ～ 1011 Mo, and ～ solar metallicity (Poster 44 Onodera).

The high SFRs, large masses and high metallicitiesof sBzKs suggest that these z ～ 2

star forming galaxies are the precursors of z=1 passive EROs and z=0 early-type galaxies.

Mambo/MIPS observations suggest sBzKs are post ULIRGs.

Summary (IV) – Number Density

4) The number density of massive pBzKs

(KVega<20, M*>1011 Mo) is about 1/5 of similarly massive early-type galaxies at z=0.

The quenching of star formation in massivestar-forming galaxies must result in a

significant growth since <z> ～ 1.7 in the number of massive, passive galaxies.

We argue that most of this star-formation quenching is likely to take place between z ～ 2 and z ～ 1.

Massive Early-type GalaxiesEvolutionary Tracks (M*>1011Mo)

z ～ 0 　　　　　　 z ～ 1 　　　　 　　 z ～ 2 　　　 z>2

Early-typ

e G

alaxies

Passiv

eE

RO

s sBzKs

pBzKs ?

sRjLsnumber density 1/5

number density 1/2

number density 1

E(B-V) ～ 0.4SFR ～ 190Mo/yr

Z ～ Zo

strong clusteringstrong clustering

strong clustering very very strong clustering

SMGs

40-200Myr

0.5-1Gyr

irregularmorphology

Passiv

eE

RO

s

Du

styE

RO

s