a wide area survey for high- redshift massive bzk galaxies x.kong, m.onodera, c.ikuta (naoj), k.ohta...
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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