1. Galaxy Evolution and WFMOS
History of Galaxies
Present-day Universe: SDSS
WFMOS Survey of z>1 Universe
K. Shimasaku (University of Tokyo)

2. Star Formation Rate Density [Msun/yr/Mpc3]
History of Galaxies：Current Understanding
redshift
peak
monotonic decrease
Star Formation Rate Density [Msun/yr/Mpc3]
first galaxies
(z～30?)
galaxy morphology
galaxy clusters
reionization
(z～10?)
birth of Earth
now
Age of Uniserve (x10 yr) 8

3. z=7.0
For high-z universes, our knowledge is limited to average (and limited) properties of bright galaxies.

4. In the present-day universe, galaxy properties depend
strongly on mass and environment.
Specific SFR vs Stellar Mass for z=0 Galaxies
spiral
Specific SFR [/Gyr]
dwarf
E, S0
Stellar Mass [Msun]
Brinchmann et al (SDSS)

5. Theory also predicts that galaxy evolution depends on
mass and environment.
ΛCDM model = Λ＋cold dark matter ＋ baryon ＋ primordial fluctuations
primordial fluctuations
hierarchical growth to more massive galaxies
complex baryon processes depending on mass,
environment, and time
gas cooling and star formation
feedback to gas
SN heating → effective in less massive galaxies
AGN heating → effective in massive galaxies
environmental effect (galaxies, ICM, UV background…)
galaxy
feedback
gas
star
cooling
environment
・these processes have not been solved
・may be missing some important processes

6. Sloan Digital Sky Survey:
A definitive data set for the present-day universe
2.5m survey telescope
mosaic CCD camera
multifiber spectrograph
- very wide field : πsteradian (1x10^8 Mpc for z<0.1)
- rich photometry : 5 bands (ugriz)
- huge number of spectra : 10^6 galaxies, 10^5 QSOs 3

7. Next Step: SDSS-like Survey for z>1 Universe
Major Science Goal:
Derive fundamental properties like
age, SFR, metallicity, dust extinction,
morphology, internal structure, QSO/AGN, SMBH
as functions of redshift, environment, and galaxy mass
At z>1 spectroscopic data are much poorer than imaging data
(cf. CfA vs SDSS for z～0 universe).
Photometric redshift cannot be a substitute for spectroscopy.
WFMOS can contribute to the above science, if excellent
imaging data pre-exist.

8. What can WFMOS do? WFMOS performance comoving length
- wide FoV: 1.77 deg2
- high multiplicity: 4500obj/FoV
- high spec resolution: R=
- high sensitivity around 1um
For a given observing time, WFMOS can
- observe much more galaxies
- observe with much higher S/N
WFMOS is thus suitable for
- statistical studies
- rare objects
- clustering and environment
- z=6-7 surveys (1um sensitivity)
Key point:
how to supply good targets to WFMOS
comoving length
for 1.5deg
comoving volume
for 1.77deg2

9. Large-scale structure covered by WFMOS
z=1
D=90Mpc
z=5
D=200Mpc
VIRGO Consortium
We should not underestimate cosmic variance.
Even one WFMOS FoV is not wide enough.

10. WFMOS Deep Sky Survey (WFDSS)
Area:
～40 deg2 (～4E+8 Mpc3/Δz=1)
Targets:
galaxies (incl. AGN) at 1<z<7.5
Number of spectra:
～1,000,000 spectra
Number of nights:
～100 nights (2hr/targets)
Imaging data for target selection:
Hyper Suprime-Cam Deep Surveys
(1) Deep Survey: 40deg2, r=27.6mag
ugrizy + NB (+NIR)
(2) Ultra Deep Survey: 3.5deg2, r=28.6mag

11. Number of Targets in WFDSS
Continuum flux-limited samples (color or phot-z):
z～1: 10^6 (i<24; M*+1.5)
z～3: 3x10^5 (i<25; M=-20.5)
z～4: 10^5 (i<25; M=-21.0)
z～5: 10^4 (z<25; M=-21.4)
z～6: 10^3 (z<25; M=-21.7)
Lyman alpha emitters: 10^4 /Δz=0.1 (NB<26)
10 Coma-cluster ancestors per Δz=1
Rare objects:
forming clusters (SSA22-like, z=5.7 cluster-like…)
forming galaxies (cooling, pop-III) etc

12. Science Cases For all redshifts For z>6
spatial distribution → environment, dark-halo mass
spectra → SFR, age, metallicity, AGN
multiband imaging → stellar mass, (SFR, E(B-V), color)
- mass- and environment-dependent galaxy evolution
(for chemical evolution, see Nagao-san’s talk)
- cluster formation, LSS formation
- primordial galaxies (cooling, pop-III)
(- number density of high-z galaxies)
For z>6
- galaxy properties and reionization processes
(Ouchi-san’s talk, Goto-san’s talk)
redshift
SFR, Mstar,
age, Z, dust,
AGN
dark-halo
mass
environment

13. Importance of Spectroscopy
3D distribution
- environment (pairs, groups, clusters, LSS, …)
- cluster and group finding
- spatial correlation function
Physical quantities
- age, SFR, metallicity, AGN, SMBH
- accurate derivation of SED, Mstar, E(B-V), …
Photometric redshifts (incl. LBG-like techniques) cannot
be a substitute.

14. Existing Spec Surveys are not Large and Deep Enough
DEEP deg2 30,000 spectra (0.7<z<1.5; 1.5E+7Mpc3)
VVDS deg2? 50,000 spectra at z>1?
zCOSMOS-deep 1 deg ,000 spectra (1.5<z<3)
Yamada Scale (T. Yamada 2008)
Survey Area
Comoving Volume
(Mpc3/Δz=1)
Main Targets
1 deg2
E+7
galaxy evolution
10 deg2
E+8
most luminous objects,
clusters, LSS
100 deg2
E+9
QSOs, cosmic web
1000 deg2
E+10
dark energy survey

15. 我々は 2 つの意味で幸運な時代にいる (1) ミクロな幸運 21世紀の現在は、銀河進化の謎に迫れる大型の望遠鏡や 装置が使える時代
- TMT, JWST, SPICA, ALMA, SKA, …
- FMOS, Hyper Suprime-Cam, WFMOS, …
(2) マクロな幸運
宇宙が100億歳余の現在は、銀河進化の全体像を観測し
得る時代
- 銀河進化の重要なできごとがちょうど終わった
- もし宇宙初期に生きていたら、質量集積、形態、downsizing、
環境効果などの銀河進化のエッセンスは、すべて未来の
できごととなり、観測できなかった
- もしずっと未来に生きていたら、銀河進化のエッセンスは
遠過ぎて観測できなかった