Culling K-band Luminous, Massive Star Forming Galaxies

at z>2

X.Kong, M.Onodera, C.Ikuta (NAOJ),K.Ohta (Kyoto),

N.Tamura (Durham),A.Renzini, E.Daddi (ESO), A.Cimatti (Arcetri), T.Broadhurst (Tel’Aviv)

N. ARIMOTO (NAOJ)

Formation of Giant Ellipticals

Massive elliptical galaxies are the products ofrecent hierarchical merging of pre-existingdisk galaxies taking place largely at z<1.5 with moderate SFRs (eg, Cole et al. 2000).

Mass Function Evolution (Baugh et al. 2002)

Fully assembled massive galaxies with Ms>1011Mo at z>2 are extremely rare.

Near IR wide field imaging is crucial.

Previous NIR Image Surveys

1. Hubble Deep Field North & South 2x5.3 arcmin2

2. K20 (NTT) 52 arcmin2

3. Subaru Deep Field (Ks=22.6) 4 arcmin2

4. Subaru XMM Deep Field (Ks=22.1) 114 arcmin2

5. Goods (HDF-N & CDF-S) 160 arcmin2

6. Hubble Ultra Deep Field (NICMOS) 5.8 arcmin2

7. EIS3a-F (Subaru/VLT, Ks=20.8) 900 arcmin2

8. Daddi-F (Subaru/VLT, Ks=19.0) 900 arcmin2

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’ (900 arcmin^2) 3σ in 2”(AB) B(AB)=27.46 R(AB)=26.87 I(AB)=26.56 z’(AB)=26.07

JK (500, 380 arcmin^2) 3σ in 2”(AB) J(AB)=23.40, Ks(AB)=22.70

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’ (900 arcmin^2) 3σ in 2”(AB) B(AB)=26.59 R(AB)=25.64 I(AB)=25.62 z’(AB)=25.31

K (715 arcmin^2) 3σ in 2”(AB) Ks(AB)=20.91

K-band Galaxy Number Counts

K-selected High-z Galaxies

780 EROs in Deep3a-F380 EROs in Daddi-F240 DRGs in Deep3a-F

1. Extremely Red Objects (EROs) McCarthey et al (1992) R-K>5.0, I-K>4.0, z>1.0, Old Passive & Dusty Star-Forming Galaxies

2. Distant Red Galaxies (DRGs) Frank et al. (2003) J-K>2.3, z>2

New Galaxy Population (BzKs)

Daddi et al. (2005): BzK=(z-K)AB-(B-z)AB>-0.2

BK20=BEIS zK20=zEIS-0.16

High-z galaxies in our fields

Star-forming galaxies at z>1.4

(BzKs) Old galaxies at z>1.4: PEGs

stars

BzKs

425 BzK in Deep 3a145 BzK in Daddi-F

B R I z’ J K

BzK(ERO) BzK BzK BzK

ERO ERO ERO ERO

Z=1.5564

VLT Observation of ～ 300 BzK galaxies

ＣＩＶ

z=1.7495

z=2.3894

ＣＩＶ

Ｌｙ α

z=2.8453Ｌｙ α

ＣＩＶ

Photometric vs Spectroscopic Redshift

VLT(ESO)

Photometric Redshift

BzKs

EROs

Photometric Redshift

DRGs

Internal reddening

•B-z (the slope of UV spectrum) color E(B-V) of SFGs.

•BzKs are dusty galaxies

•ERO: OGs & DGs have different internal reddening.

Kong, Charlot, Brinchman, Fall (2004)

BzK ERO

Stellar Mass

Stellar mass : based on multi-color photometry

EROs and BzKs are similar (on average)

30% BzKs & EROs : M>1.0E11M @ Deep3a-F Klim=20.2 mag

55% BzKs & EROs : M>1.0E11M @ Daddi-F Klim=18.8 mag

BzKs EROs

Star Formation Rate

NIR spectra (Subaru)• Dad1901

SFR(Ha)=60 M/yr

SFR(UV)=70 M/yr

• Dad2326SFR(Ha)=250 M/yr

SFR(UV)=180M/yr

• BzKs have high SFRs

• EROs : OGs/DGs diff.

UV Flux: 1500A<λ<2800A

burst age reddening

stellar mass SFR

Culling K-band Luminous, Massive Star Forming Galaxies at z>2

Sky positions of BzKs & EROs

Angular two-point correlation function: Landy & Szalay (1993)

w(q)= (DD-2DR+RR)/RR ＝ Aq-d (d=0.8)

BzKs EROs

Clustering Properties

Field Galaxies Field Galaxies

EROs EROs

BzKs BzKs

A New Population of near-IRbright, z ～ 2 Galaxies

K>20 HST/ACS F435W, F850LP & K-band (VLT+ISAAC)

A sample of 9 galaxies at 1.7<z<2.23 with bright K-band magnitudes 18.7<K<20 has recently been discovered (Daddi et al. 2003, astro-ph/0308456).

Summary• BzKs

– High internal reddening : E(B-V) ～ 0.5– strong star formation : SFR ～ 200 M/yr– Massive galaxies : >30 ％ (K=20)

M>1.0E11M – Strong 2-D clustering

• EROs (R-K>5) : DGs & OGs– OGs: passive galaxies– DGs: some of them are BzKs– OGs have low SFRs– Strong clustering and massive

• LBGsE(B-V)≤0.3, SFR< 70 M/yr, clustering

Summary

BzK selection is a quite powerful way to separatestar forming galaxies at 1.4<z<2.5.

BzKs are different from LBGs (low extinction, low SFR).Some BzKs are dusty EROs (high extinction, low SFR),but most of BzKs are not EROs.

K-band luminous, massive, high-SFRs galaxies at z>2are likely to be possible precursors of z ～ 1 passivelyevolving EROs and z=0 elliptical galaxies.

Submm galaxies are sub-populations of BzKs with extremely high SFRs and metallicities.

Conclusions

We have discovered a new population of reddened, vigorous star-forming massive galaxies at z>2.Their masses, likely extremely high star formation rates, HST/ACS morphologies, clustering properties,all suggest that they may be the long-sought-forprogenitors of nearby massive ellipticals, close totheir epoch of formation.What Next?1) Confirming the High SFRs, High metallicity2) Contribution to the z>2 SFR Density3) Understand the link between BzK and Submm Gals4) CO follow-up5) Co-evolution of BzK and Massive BHs ………6) COSMOS, NEP. SXDS, etc to see cosmic variance