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Galaxy Evolution and WFMOS
History of Galaxies
Present-day Universe: SDSS
WFMOS Survey of z>1 Universe
K. Shimasaku (University of Tokyo)
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History of Galaxies：Current Understanding
Star Formation Rate Density
[Msun/yr/Mpc3]
redshift
peak
galaxy morphology
galaxy clusters
birth of Earth
now
first galaxies
(z～30?)
reionization
(z～10?)
Age of Uniserve (x10 8 yr)
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z=7.0
For high-z universes, our knowledge is limited to
average (and limited) properties of bright galaxies.
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In the present-day universe, galaxy properties depend
strongly on mass and environment.
Specific SFR vs Stellar Mass for z=0 Galaxies
Specific SFR [/Gyr]
spiral
dwarf
E, S0
Stellar Mass [Msun]
Brinchmann et al. 2004 (SDSS)
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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…)
・these processes have not been solved
・may be missing some important processes
galaxy
feedback
gas
star
cooling
environment
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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 Mpc3 for z<0.1)
- rich photometry : 5 bands (ugriz)
- huge number of spectra : 10^6 galaxies, 10^5 QSOs
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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.
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What can WFMOS do?
WFMOS performance
- wide FoV: 1.77 deg2
- high multiplicity: 4500obj/FoV
- high spec resolution: R=3000-40000
- high sensitivity around 1um
comoving length
for 1.5deg
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)
comoving volume
for 1.77deg2
Key point:
how to supply good targets to WFMOS
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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.
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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
ugrizy + NB (+NIR)
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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
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Science Cases
For all redshifts
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
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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.
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Existing Spec Surveys are not Large and Deep Enough
DEEP2
3.5 deg2 30,000 spectra (0.7<z<1.5; 1.5E+7Mpc3)
VVDS
2 deg2? 50,000 spectra at z>1?
zCOSMOS-deep 1 deg2
10,000 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
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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
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