理論懇シンポ（立教大学, 25/12/2006）

最近の遠方銀河観測による銀河形成の諸問題
Mass assembly / Down sizing / Dust extinction

今、歴史が動いている。

児玉 忠恭（国立天文台、光赤外研究部）“Panoramic View of Praha” (13/08/05)

Theoretical Views for Cluster/Galaxy Formation
15

12Cluster Formation (10 Mo)

Galaxy Formation (10 Mo)

z = 30z=5z = 25

z=3z=3z=2z=2z=1z=1z=0z = 0.5z=0

Yahagi et al. (2005)

Bekki & Chiba (2001)

In the standard cosmological models (CDM), small scale objects collapse
first and they assemble by gravity to form bigger and bigger systems with time.

Panoramic Views of Cluster AssemblyDistribution of phot-z sliced galaxies (Δz =−0.05~+0.03)
RXJ 0152.7-1357 (VRIz’)
CL 0016+16 (BVRi’z’)

z=1

z=0.83 (7.0 Gyr ago)simulation

z=0.55 (5.4 Gyr ago)
Kodama, et al. (2005)

Unsolved Issues on Galaxy Formation andEvolution from An Observer’s Point of View
 When are the massive galaxies assembled ?

Is it consistent with hierarchical models ?
 What is the origin of down-sizing ?

Is it consistent with the bottom-up picture ?
 What is the sampling bias in high-z galaxies ?

What is the effect of dust ?
RXJ0152.7-1357 (z=0.83), Subaru

 When are the massive galaxies assembled ?

Is it consistent with hierarchical models ?

Formation of massive galaxies: late assembly?
Bekki & Chiba (2001)

Baugh et al. (2002)
semi-analytic modelz=3 2 10Mstars

Stellar mass function is expected to dramatically change with timein the hierarchical galaxy formation models.
see also Kauffmann & Charlot (1993)

Stellar mass evolution at z<2K20 (52 arcmin^2)

UKIDSS-UDS (0.6 deg^2)

H160=26.5

Pozzetti et al. (2003)

Cirasuolo et al. (2006)
No significant evolution at the massive-end of SMF out to z~1.5

Stellar mass evolution at z>2
Distant Red Galaxies (J-K>2.3; DRG) at 2<z<3153 DRGs in GOODS-S

Papovich et al. (2006)

Many of them have stellar masses
greater than 10^11 Msun !
Host ~80% of stellar mass at 2<z<3.

Franx+ (03), van Dokkum+ (03; 04; 06), Foerster Schreiber+ (04)…

Stellar mass evolution at z>2z~0.5z~0.7z~1.45

GOODS-MUSIC (160 arcmin^2) withSpitzer bands.
Fontana et al. (2006)z~1.8

At z>1.5-2, co-moving number density ofmassive galaxies starts to decrease.
FDF+GOODS-S (90 arcmin^2), U to Kz~0.9

z~2.5z~1.15

z~3.5
MstarsDrory et al. (2005)

The spider-web galaxy(witnessing the assembly of a cD at z=2.16)

Miley et al. (2006)

Hierarchical models tend to underpredict massive galaxies even at z<1
Cimatti et al. (2006)
fraction of massive galaxies vs redshiftobs
modelObs vs Semi-analytic Model (De Lucia+ 06)
MB(z=0)SDSS(z~0) vs. COMBO17(0.2<z<1) vs. DEEP2(0.3<z<1.1) vs. SXDS (z~1)

Recent models do a better job
Stellar mass density

Stellar mass function
modelsobsmodelsobs

z~1
Mstars(semi-analytic with AGN feedback)Bower+06
Nagamine+05(SPH)

Fontana et al. (2006)
GOODS-MUSIC~8000 galaxies with Ks<23.5 (AB)JHK selection of 2<z<3 galaxies
DRG
JHK

Classical criteria (DRG):
J-K>2.3
passive/dusty gals at z>2

z=0

Kajisawa et al. (2006), Kodama et al. (2006)

Our new criteria (JHK):(J-K)> 2(H-K)+0.5&& J-K>1.5
passive/dusty +star-forming gals at 2<z<3JHK selection of 2<z<3 galaxies
r-JHK

Classical criteria (DRG):
J-K>2.3
passive/dusty gals at z>2b-JHK

Our new criteria (JHK):(J-K)> 2(H-K)+0.5&& J-K>1.5
passive/dusty +star-forming gals at 2<z<3J-K>2.3 -- r-JHK
J-K<2.3 -- b-JHK

JHK diagram (0943@z=2.923)
USS0943 (z=2.923)

GOODS-S (blank field)● pJHK ● sJHK

RG☆

25 arcmin^225 arcmin^2

Excesses of both r-JHK and b-JHK are clearly seen (factor>2.5).
Kodama et al. (2006)

Colour-Magnitude (1138@z=2.156)
PKS1138 (z=2.156)

GOODS-S (blank field)● DRG(J-K>2.3)

Kodama et al. (2006)

Well-visible red sequence consistent with passive evolution formed at z~4-5.
They are very massive (>10^11Msun) !

Colour-Magnitude (0943@z=2.923)
USS0943 (z=2.923)

GOODS-S (blank field)○● DRG(J-K>2.3)● r-JHK ● b-JHK

Kodama et al. (2006)

Clear excess of red galaxies consistent with passive evolution formed at z>4,
but few massive ones (>10^11Msun) ! Æ not assembled yet !?

What’s the era of 2 < z < 3 ?
SCUBA sources peak at z~2.4

Chapman et al. (2005)

Cosmic SFR peaks at z~3

Bouwens et al. (2005)⊿ｔ(2<z<3)

100 Msun/yr × 1 Gyr = 10^11 Msun

2-D Structure of PKS1138 (z=2.156)
Map of both Stellar Mass and Star Formation !
(evolved gals.)(young gals.)simulation
z=2

MOIRCSRG☆

● DRG(J-K>2.3)● DRG(J-K>2.3) ○Lyα △Hα＊Lyα(11 confirmed)

see also
Kurk et al. (2004)
Croft et al. (2005)

2-D Structure of USS0943 (z=2.923)
simulation
z=3RG

☆

MOIRCS○●DRG(J-K>2.3) ● r-JHK ● b-JHK○Lyα ＊Lyα(25 confirmed)

A Post-Starburst Galaxy at z~6.5 ?
Mobasher et al. (2005)

E(B-V)

K(Vega)=22Redshift
13~18 massive galaxies at ｚ>5 have also been found.
Mstar = 6 × 10^11 Msun ！
（<M*>=2x10^11Msun）

Stellar mass of galaxies at frontier redshifts
1-4 x 10^10 Msun

10^9 ~ 10^10 Msun

Balmer break

Balmer breakz=6 (i’-drop), Eyles et al. (2005)

z=7 (z’-drop), Labbe et al. (2006)

Break features require relatively old stars formed in the re-ionization era (zf~10).

Lack of re-ionization sources?
Required SFR tokeep re-ionization

Observed stars

53 i’-band dropouts in GOODS.

Massive galaxies at z~6 cannot sustain
re-ionization Æ Contribution from dwarfs!

10^9~10^10 Msun
>1% of stellar mass in local Universe
Yan et al. (2006)
is locked in stars at z~6.

Morphology first appeared between
z=1 and 2?
z ~ 1 (8Gyr ago)z ~ 2-3 (10~11Gyr ago) LBGs

λrest=1700Å, 4300Å
λrest=3000Å, 6500Å

4 x4 arcsec^2 squares
Dickinson (2000), HDF-N

Large Disk Galaxies at 1.4<z<3
WFPC2(HST) + ISAAC (VLT) 102hr JHK imaging in HDFS

Re 〜 5--7.5 kpc !

Labbe et al. (2003)

Rotation of a distant disk galaxy
IFU(SINFONI, VLT) + AO Æ 0.15” resolution (~1.2kpc@z=2.38)

z=2.38, Ks=19.2, Mdyn=1.13*10^11Msun (Vc=230km/s),
M*=7.7*10^10Msun, Re=4.5kpc , Mgas(Ha)=4.3*10^10Msun
Genzel et al. (2006, Nature) See also Foerster-Schreiber et al. (2006)

Rotation of distant disk galaxies
IFU(SINFONI, VLT), 0.5” seeing (~4kpc@z=2)

Foerster-Schreiber et al. (2006)

“Fast Formation of Massive Galaxies”
in all aspects:
Star formation, Mass assembly, and Morphology.

 What is the origin of down-sizing?

Is it consistent with the bottom-up picture ?

Down-Sizing in Star Formation
SDSS (z=0)

SXDS (z=1, 1.2deg^2)

critical mass

red+bright=blue+faintU-V1098log Mstar
Kauffmann et al. (2003)
see also Bell et al. (2004) for COMBO-17

R-z’ (colour)

red+brightblue+faint11z’ (magnitude)
Kodama et al. (2004)
see also De Lucia et al. (2004) for EDisCS

Massive galaxies are old, while less massive galaxies are younger or havemore extended star formation: Æ “Down-sizing”!

Down-sizing seen in the FP to z~1
GOODS (141 field early-types)

CDFS/1252 (27 field early-types)

van der Wel et al. (2005)
Treu et al. (2005)
Less massive galaxies tend to have larger deviation in M/L ratio
compared to local FP, suggesting their younger ages.

Down-sizing seen in chemical evolution
Erb et al. (2006)

Onodera (2005), PhD thesis

SDSS(z=0)z~2log Mstar[NII]/HαÆ (O/H)

12+log(O/H)

12+log(O/H)

sBzK(z~2)
SMG(z~2.4) DRG(z~2.3)
LBG(z~2.2)
SDSS(z=0)
GDDS/CFRS(z=0.7)

log Mstar

Chemical Evolution
Star Formation History

Down-sizing seen in Mg/Fe ratio

Obs

Model
faintLower Mg/Fe ratio towards smaller ellipticals
suggesting longer timescale of star formation.

brightThomas (2001)
Ap&SS, 277, 209Down-sizing in star formation
as a function of Time
8,000 galaxies at 0.4<z<1.4 from DEEP2 Redshift Survey
0.40<z<0.70
4.3<t(Gyr)<6.3

0.75<z<1.00
6.5<t(Gyr)<7.7

blue galaxies

red galaxies

The critical massthat separate
red/blue pops shifts
to lower mass astime progresses!

1.00<z<1.40
7.7<t(Gyr)<8.4

highlog Mstar

low

Bundy et al. (2006)

Down-sizing as a function of Environment!
red/blue galaxies
RXJ0152 (z=0.83)

CL0016 (z=0.55)

Tanaka, TK, et al. (2005)

SDSS (z=0)

Star Formation Histories of Galaxies
vs. Mass and Environment

Thomas et al.
(2005)

high-mass/high-density Æ low-mass/low-density

Interpretation of Down-Sizing
Millennium simulation (N-body) + Munich semi-analytic modelStar formation
Mass assemblyM<4*10^9 M>10^11 Msun

M>10^11 Msun

50%

50%
M<4*10^980%

80%

Massive (E) galaxies form stars earlier (intrinsic bias), but areassembled later than less massive galaxies. De Lucia et al. (2006)

“Slow/Delayed Formation ofLow Mass Galaxies
and in Low Density Regions”

How can we extend star formation in such small systems
where SN feedback can easily expel the gas?
Extremely low SF efficiency? Gas fall back?
Interaction with host galaxies?

 What is the sampling bias in high-z galaxies?

What is the effects of dust ?

High-z Zoo

BzK
JHK

ERO
DRG

SMG

SFR
SSFR =Mstar

LAE
LAB

Mstar

LBG

Evolutionary state of each class of galaxies
on a stellar-mass limited sample!
SSFR ~ b (birth parameter) ~ f_gas (Schmidt law) = “evolutionary state”

Star formation is largely hidden inoptical surveys!
Reddy et al. (2006)

ext. corr.

Uncertainty in cosmic star formation
history is dominated by correction for
dust extinction.

L(FIR)/L(1600A)

Bouwens et al. (2005)

Even if you correct for extinction using
UV spectral index, you still tend tounder-estimate SFR for dusty galaxies.

Improvement in estimates of stellar massand photometric redshift with Spitzer bands
M(with Spitzer) / M(without Spitzer)

Fontana et al. (2006)
Dramatic improvement in stellar mass estimates at z>2.

Model dependence in Mstars

BC03 model overestimates stellar mass
TP-AGBs have significant contribution
by factor 1.6 compared to M05.
at rest-frame NIR at ~1Gyr.
Maraston et al. (2006)
Æ CB07 models have now included TP-AGB.

24 micron flux measures dusty SFR at z~2
SFR of 69 MIPS detected DRGs

Webb et al. (2006)
24μm samples ＰＡＨ dust features (6.2-8.6um)
from z~2 galaxies, which are good measuresof dusty star formation rate (Chary & Elbaz 2001).

SFR=30~1000 Msun/yr(average 130Msun/yr).
DRG contribute 20% ofSFRD at z~2.

Discrimination between Passive/Dusty/AGN
Wilson et al. (2006)

passiveAGN

dusty-starburst

see also Stern+ (05),and Webb+ (06)Ultimate diagram to quantify galaxy evolution
SSFR=SFR/M* versus M*
SFR (UV+IR) / Mstars

young

LBG

BzK
HDF-N
DRG

DRG

oldReddy et al. (2006)

Papovich et al. (2006)

See also Erb et al. (2006) for Hα based SSFR vs M*.

〜 From “zoo” to “science museum” 〜

めだち系

youngLAE
LAB

SMG
きたな系

LAE

old

BzK
BzK
Path ①bottom-up
small

LBG

Path ②

instantaneous

LBG

SFR
SSFR =Mstar
うるさ系

SMG
DRG

BzK
JHK

ERO

ふてい系

BLG (bulge)
Mstar

large

ERO
DRG

いやし系