Culling k band luminous massive star forming galaxies at z 2
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Culling K-band Luminous, Massive Star Forming Galaxies at z>2. N. ARIMOTO (NAOJ). 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). Formation of Giant Ellipticals.

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Culling k band luminous massive star forming galaxies at z 2
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)

Formation of giant ellipticals
Formation of Giant Ellipticals z>2

Massive elliptical galaxies are the products of

recent hierarchical merging of pre-existing

disk galaxies taking place largely at z<1.5

with moderate SFRs (eg, Cole et al. 2000).

Near IR wide field imaging is crucial.

Fully assembled massive galaxies with

Ms>1011Mo at z>2 are extremely rare.

Mass Function Evolution

(Baugh et al. 2002)

Previous nir i mage s urvey s
Previous z>2NIR 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
Subaru/Sup-Cam Observation z>2

ESO Imaging Survey (EIS Deep 3a) Field

RA=11:24:50, DEC=-21:42:00 (J2000.0)

Subaru/Suprime-Cam BRIz’: 2003/03/02-04

NTT/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 observation1
Subaru/Sup-Cam Observation z>2

Daddi Field

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

Subaru/Suprime-Cam BIz’: 2003/03/02-04

WHT R : 1998/03/19-21

NTT/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)


K selected h igh z g alaxies
K-selected z>2High-z Galaxies

  • 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

780 EROs in Deep3a-F

380 EROs in Daddi-F

240 DRGs in Deep3a-F

2. Distant Red Galaxies (DRGs)

Frank et al. (2003)

J-K>2.3, z>2

New galaxy population bzks
New Galaxy Population (BzKs) z>2

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

B z>2K20=BEISzK20=zEIS-0.16

High z galaxies in our fields
High-z galaxies in our fields z>2

Star-forming galaxies at z>1.4 (BzKs)

Old galaxies at

z>1.4: PEGs



425 BzK in Deep 3a

145 BzK in Daddi-F

B R I z z>2’ J K

BzK(ERO) BzK BzK BzK z>2


Z=1.5564 z>2


VLT Observation of ~300 BzK galaxies

Ly z>2α



Ly z>2α



Photometric redshift
Photometric Redshift z>2



Internal reddening
Internal reddening z>2



  • 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)

Stellar mass
Stellar Mass z>2



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

Star Formation Rate z>2

UV Flux: 1500A<λ<2800A

NIR spectra (Subaru)

  • Dad1901

    SFR(Ha)=60 M/yr

    SFR(UV)=70 M/yr

  • Dad2326

    SFR(Ha)=250 M/yr


  • BzKs have high SFRs

  • EROs : OGs/DGs diff.

burst age z>2


stellar mass


Sky positions of bzks eros
Sky positions of BzKs & EROs z>2



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

    • w(q)= (DD-2DR+RR)/RR=Aq-d (d=0.8)

Clustering properties
Clustering Properties z>2

Field Galaxies

Field Galaxies





A new population of near ir bright z 2 galaxies
A New Population of near-IR z>2bright, 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).

Summar y
Summar z>2y

  • 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

  • LBGs

    E(B-V)≤0.3, SFR< 70 M/yr, clustering

Summary z>2

BzK selection is a quite powerful way to separate

star 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>2

are likely to be possible precursors of z~1 passively

evolving EROs and z=0 elliptical galaxies.

Submm galaxies are sub-populations of BzKs with

extremely high SFRs and metallicities.

Conclusions z>2

  • 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-for

  • progenitors of nearby massive ellipticals, close to

  • their epoch of formation.

  • What Next?

  • Confirming the High SFRs, High metallicity

  • Contribution to the z>2 SFR Density

  • Understand the link between BzK and Submm Gals

  • CO follow-up

  • Co-evolution of BzK and Massive BHs ………

  • COSMOS, NEP. SXDS, etc to see cosmic variance