Post on 20-Jan-2016
Subaru Galaxy Surveys: Subaru Galaxy Surveys: Hyper-Suprime Cam & WFMOSHyper-Suprime Cam & WFMOS
(As an introduction of next talk by (As an introduction of next talk by Shun SaitoShun Saito))
Masahiro Takada
(Tohoku Univ., Sendai, Japan)
Sep 11 07 @ Sendai
CMB + Large-Scale Structure (LSS)CMB + Large-Scale Structure (LSS)
+
WMAP (z~10^3)
LSS (0<z<3)
SDSS (Tegmark etal03)
Complementarity btw CMB and LSSComplementarity btw CMB and LSS
• CMB probes the statistical properties of fluctuations at z~10^3– All the fluctuations are well in the linear regime: clean info– Linear perturbation theory predictions, which are robust and secur
e, can be compared with the measurements• A galaxy survey probes the density perturbations at low redshift
s (0<z<3)– The perturbation amplitudes significantly grow from z~10^3, by a
factor of 10^3 at least– An uncertainty in the model predictions arises from non-linearities
in structure formation• Combining the two is very powerful (e.g., WMAP + SDSS)
– Opens up a window to probe redshift evolution of the perturbations, which helps break parameter degeneracies
– Allow to constrain the neutrino mass – Very complementary in redshift and wavenumbers probed
(e.g., Eisenstein, Hu & Tegmark 98)
Linear growth rate (a case of CDM model)Linear growth rate (a case of CDM model)
€
δ(x;z) ≡ρ(x;z) − ρ (z)
ρ (z)
€
˙ ̇ δ k + 2H ˙ δ k − 4πGρ mδk = 0
• The density perturbation in the LSS, observable from a galaxy survey
• Linear growth describes the time-evolution of the density perturbations, form the CMB epoch (z~10^3)– In the matter-dominated regime, the CDM perturbations of different
wavelengths grow at the same rate– Combining the FRW eqns and the linearized GR+Boltzmann eqns l
eads to the second-order differential equation
• Alternative, yet interesting ingredients– The cosmic acceleration slows down the growth– Adding massive neutrinos leads to suppression in the growth at low
redshifts and on small scales
CDM Structure Formation Model: P(k)CDM Structure Formation Model: P(k)
Amplification in the density perturbation amplitude by a factor of 1000, between z=0 and 1000.CMB
Galaxy Survey
k3 P(k
,z)/
22 ~
<δ2
>R
~1/k
WL
Massive neutrinos and LSSMassive neutrinos and LSS
mmttotot>0.06 eV>0.06 eV mmttotot>0.11 eV>0.11 eV
€
Ωm = Ωcdm + Ωbaryon + Ων : fν ≡ ΩνΩm
> 0.005
• The experiments imply the total mass, m_tot>0.06 eV
• Neutrinos became non-relativistic at redshift when T,dec~m
• Since then the neutrinos contribute to the energy density of matter, affecting the Hubble expansion rate– The cosmological probes (CMB, SNe, BAO …) measure
• The massive neutrinos affect the CMB spectra, mainly through the effect on H(z) (see Ichikawa san’s talk)– The effect is generally small, also degenerate with other cosmo paras.
€
1+ znr ≈1890 mν 1eV( )
Suppression in growth of LSSSuppression in growth of LSS• Neutrinos are very light compared to CDM/baryon: the free-stre
aming scale is ~100Mpc (for m~0.1eV), relevant for LSS– At a redshift z
• The neutrinos slow down the growth of total matter pert.– On large scales >fs, the neutrinos can grow together with CDM
– On small scales <fs, the neutrinos are smooth, δ=0, therefore weaker gravitational force compared to a pure CDM case
)(xδ
Total matter perturbations can grow!
CDM CDM
< fs > fs
Suppresses growth of total matter perturbations
€
fs(z) ≈ vν H−1a−1 ⇒ kfs(z) ≈0.68
(1+ z)1/ 2
mν
1eV
⎛
⎝ ⎜
⎞
⎠ ⎟Ωm
1/ 2h Mpc−1
€
˙ ̇ δ + 2H ˙ δ − 4πGρ m (1− fν )δ = 0
Suppression of growth rate (contd.)Suppression of growth rate (contd.)
Suppression of growth rate (contd.)Suppression of growth rate (contd.)12/12,1/2-
fs,i Mpc)(eV1
z)0.68(1)( −Ω⎟⎟⎠
⎞⎜⎜⎝
⎛+≈ h
mzk m
i
k_fs
The suppression is stronger at lower redshifts, implying the usefulness of CMB+LSS to probe the neutrino effect
E.g., the current limit on the total neutrino mass, m_tot<0.9 eV (95%) from WMAP +SDSS (Tegmark etal. 06)
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Hyper Suprime-Cam (HSC)Hyper Suprime-Cam (HSC)• Replace the Subaru prime focus cam
era with the new one (HSC)
• PI: S. Miyazaki (NAOJ)
• The grant (~$15M) to build the new camera was approved in 2006
• Construction: 2006-2011
• FoV: 1.5 - 2.0 degrees in diameter (~10 the Suprime-Cam’s FoV)
• 4 - 5 broad band filters (BVRiz) available
• The first light in 2010 - 2011
• Plan to conduct a wide-field survey (primarily for WL); hopefully starting from 2011 for 3-5 years
From Y. Komiyama 2 degree FoV option
Suprime-Cam
WFMOS (Wide Field Multi-Object Spectrograph)WFMOS (Wide Field Multi-Object Spectrograph)
Glazebrook et al. astro-ph/0507457
Echidna
• Survey area 2000 deg^2 @ 0.5<z<1.3 (ng~1000deg-2), 300deg^2 @ 2.5<z<3.5 (ng~2000 deg-2) ~300 nights
• Primary science cases: dark energy, neutrinos…
Proposed galaxy redshift survey
• The project originally proposed by Gemini observatory (US+Europe+) to Japan (2005-)
• Now seriously considered as a next-generation Subaru instrument: in the phase of the feasibility/design study
• Assume the HSC FoV
• 2000-4000 fibers
• If fully funded (>~$50M): the first-light 2015(?)-, after HSC
Advantage of high-redshift survey (I)Advantage of high-redshift survey (I)
• For a fixed solid angle, a higher-redshift survey allows to cover a larger 3D comoving volume– A more accurate measurement of P(k) is av
ailable with a larger surveyed volume
– A planned WFMOS (z~1 survey with 2000 deg^2 + z~3 survey 300 deg^2)
– ~4 (z~1) + ~1 (z~3) = ~5 h-3 Gpc3
– For comparison, SDSS (z~0.3) covers
~1 h-3 Gpc3 with 4000 deg^2 (Eisenstein etal 05)
– V_wfmos ~ 5 V_sdss
Ω_s
Advantage of high-redshift survey (II)Advantage of high-redshift survey (II)
• At higher redshifts, weaker non-linearities in LSS– A cleaner cosmological info is
available up to kmax
– SDSS: kmax~0.1 h/Mpc
– WFMOS• z~1: kmax~0.2 h/Mpc
• z~3: kmax~0.5 h/Mpc
• Surveyed volume in F.S. – V_wfmos(k)~30V_sdss(k)
• In total, accuracy of measuring P(k): 2(lnP(k))~1/[V_sV(k)]
Springel etal. 2005, Nature
€
WFMOS2 (lnP) ~ 0.01σ SDSS
2 (lnP)
A measurement accuracy of P(k) for WFMOSA measurement accuracy of P(k) for WFMOS
• WFMOS allows a high-precision measurement of P(k)
• The characteristic scale-dependent suppression in the power of P(k) due to the neutrinos could be accurately measured (see Saito kun’s talk)
Neutrino suppress.0.6% of Ω_m~4% effect on P(k)
The parameter degeneracy in P(k)The parameter degeneracy in P(k)
• Different paras affect P(k) in fairly different ways
• Combining galaxy survey with CMB is an efficient way to break degeneracies btw f_nu, n_s and alpha (MT, Komatsu & Futamase 2005)
€
Pprimord (k)∝k
k0
⎛
⎝ ⎜
⎞
⎠ ⎟
n _ s+(1/ 2)α ln(k / k0 )
k0 = 0.002 Mpc-1
Different probes are complementaryDifferent probes are complementary
From Tegmark+04
SummarySummary • CMB+LSS opens up a new window of constraining th
e neutrino mass, from the measured suppression in the growth of mass clustering
• A higher redshift survey, such as the survey of planned Subaru survey, allows a precise measurement of the galaxy power spectrum
• Need to develop more accurate theoretical predictions of P(k) for a mixed DM model that allow a secture comparison with the precise measurement (see Saito kun’s talk!)
Suppression Suppression in P(k)in P(k)
• Assume 3 flavors when relativistic– Consistent with
CMB and BBN
• Assume N species become NR (or are massive) at low-z
• Suppression has scale-dependence
• P(k) amplitude is normalized by the primordial Pi(k)
• All P(k) have same amount suppression on sufficiently large k.
WFMOS z~3 slice
f=0.05 (Ω=0.014)
f=0.01 (Ω=0.003)
Forecasted erroForecasted errors for neutrino rs for neutrino
parasparas• 2D galaxy P(k) is very
powerful to constrain mtot
– N.O. experiment neutrinos can be weighed at more than 1: (mtot)=0.03eV
• Relatively difficult to constrain N and mtot independently.– If mtot>0.45eV, models
with N= 1 can be discriminated at more than 1-sigma level
WFMOS Can Measure DE Clustering?WFMOS Can Measure DE Clustering?
• Another important consequence of DE with w-1 is its spatial clustering, de(x,t)
• A useful way: explore fluid properties of DE (δde, δpde, d
e,… ), instead of modeling a form of DE Lagrangian
• Sound speed ce (δpde) defines the free-streaming scale of DE clustering (e.g., quintessence, c_e=1)
> fs : DE can cluster with DM
< fs : DE perturbations are smooth (δde=0)
dedemm δδδ +=t
aaH
cdaa ea
)()(
0de ∫=
mmδδ ≈t
(MT 06 soon)
Effect on Effect on PP(k)(k)
Sensitivity of WFMOS to DE perterbatSensitivity of WFMOS to DE perterbationsions
• If c_e<0.1, WFMOS can measure the DE perturbations at more than 1-sigma significance.
• The power is compatible with an all-sky imaging survey (CMB-galaxy cross-correlation, Hu & Scranton 04).
SummarySummary• Hyper-Suprime/WFMOS survey will provide an ultimate, i
deal dataset for performing BAO as well as WL tomography experiments.
• BAO and WL are complementary for DE constraints, and more important is the independent two methods from the same surveyed region will be very powerful to test various systematics. – Issue for WL: Need to study which type of galaxies gives a fair samp
le of WFMOS sample
• Current survey design (~2000deg2, 4 or 5 colors, ng~0.3/arcmin2 or ng~510-4 h3 Mpc-3) seems optimal for joint BAO and WL experiments.
• Valued Sciences: WFMOS can do– Neutrino Mass: sigma(mtot)=0.03eV– Dark energy clustering
• In this case, z<1 survey is crucial for doing this (z~3 survey can’t do)– Inflation parameters (ns and alpha): ~10^-3– Having a well-defined survey geometry is crucial: optimal survey str
ategy?