2015/12/14 Dark Side of the Universe 2015 @YITP

Cosmology withthe Square Kilometre Array(by SKA-Japan)
Daisuke YAMAUCHI
Research Center for the Early Universe,
The University of Tokyo,
On behalf of SKA-Japan Consortium (SKA-JP)
Cosmology SWGSQUARE KILOMETRE ARRAY Open a new window for Astronomy
 New frequency regime

 Wide sky coverage high angular resolution
 High sensitivity

MID (ν=0.35-10GHz)

LOW (ν=0.05-0.35GHz)

SKA Phase 1(2018 – 2023)
Phase 1:130,000 antennas across
80km of Australia

Phase 1:200 dishes across 150kmof Southern Africa

Phase 2:500,000 antennas across
200km of Australia(2025 – 2033)

Phase 2:2,500 dishes across
3500km of Southern Africa(2025 – 2033)

Scientific goals of SKA
The SKA aims to solve some of the biggest questions.
 Fundamental physics : Gravity, Dark Energy,
Cosmic Magnetism
 Astrophysics : Cosmic Dawn, First galaxies,galaxy assembly and evolution, +…

？

 The unknowns : transients + ...

Dark Energy

Cosmic Dawn

MagnetismGalaxy &Transients

Gravity

Science WG of global SKA
(Global) Science working group

Epoch of Reionization
Continuum
Cosmology
Cradle of lifeHI galaxy science
Magnetism
Pulsars
TransientsFocus group Our galaxy, Spectral lines, VLBI

Cosmic Dawn

MagnetismGalaxy &Transients？
Dark Energy

GravitySKA-Japan Consortium
Chair：Sugiyama Nagoya U[187 members (Sep.2015)]

Advisors：
Kobayashi NAOJ Honma NAOJ
Publicity：
Nakanishi* Kagoshima U
Funding：
Imai* Kagoshima U

Vice Chair：
Akahori* Kagoshima U
Takahashi* Kumamoto U
Engineering WG：
Aoki* Waseda U

Science WG：
Ichiki* Nagoya

Software：
Kurayama Teikyo
Feed：Ujihara NICT
Signal process：Nakanishi* Kagoshima U

Industry forum：
Kumazawa Toyo corp.
Industry

High-z galaxies：
Hirashita ASIAA
Cosmology：
Yamauchi* U Tokyo
Reionization：
Hasegawa* Nagoya U

Galaxy evolution：
Takeuchi* Nagoya U(*)global
SKA SWG
Pulsars：

Takahashi* Kumamoto U

Astrometry：
Imai* Kagoshima U
Interstellar medium：
Tachihara* Nagoya U
Transients：
Aoki* Waseda U
Magnetism：
Machida Kyushu U

SKA-Japan Consortium
Chair：Sugiyama Nagoya U[187 members (Sep.2015)]

Advisors：
Kobayashi NAOJ Honma NAOJ
Publicity：
Nakanishi* Kagoshima U
Funding：
Imai* Kagoshima U

Vice Chair：
Akahori* Kagoshima UTakahashi* Kumamoto U
Engineering WG：
Aoki* Waseda U

Science WG：
Ichiki* Nagoya

Software：
Kurayama Teikyo
Feed：Ujihara NICT
Signal process：Nakanishi* Kagoshima U

Industry forum：
Kumazawa Toyo corp.
Industry

High-z galaxies：
Hirashita ASIAA
Cosmology：
Yamauchi* U Tokyo
Reionization：
Hasegawa* Nagoya U

Galaxy evolution：
Takeuchi* Nagoya U(*)global
SKA SWG
Pulsars：

Takahashi* Kumamoto U

Astrometry：
Imai* Kagoshima U
Interstellar medium：
Tachihara* Nagoya U
Transients：
Aoki* Waseda U
Magnetism：
Machida Kyushu U

SKA-Japan Science Book
 In Japanese (published; 316 pages)
1. Introduction
2. Reionization
3. Cosmology
4. Galaxy Evolution
5. Pulsars
6. Cosmic Magnetism
7. Astrometry
8. Interstellar Medium
9. Transients
10. Summary Now being translated in English
http://ska-jp.org/ws2015/SKA-JP/talks/SKAJP_Science_Book_2015.pdf

SKA-Japan Science Book SKA-JP Cosmology SWG
D. Yamauchi (Tokyo, Chair)
K. Ichiki （Nagoya）
K. Kohri (KEK, Sokendai)
Y. Oyama (ICRR)
T. Sekiguchi (Helsinki)
H. Shimabukuro (Kumamoto)K. Takahashi (Kumamoto)T. Takahashi (Saga)
S. Yokoyama (Rikkyo)
K. Yoshikawa (Tsukuba)

Plan
1. Introduction

2. Cosmology with the SKA: brief review
3. Cosmology with the SKA
by SKA-JP Cosmology SWG
4. Summary

Plan
1. Introduction

2. Cosmology with the SKA: brief review
3. Cosmology with the SKA
by SKA-JP Cosmology SWG
4. Summary

Hydrogen 21cm-line
λ = 21 cm (ν=1.4GHz)

pe

proton electronpeproton electron Hyperfine transition of neutral hydrogen (HI) Characteristic line emission with λ=21cm

 HI mainly lives inside galaxies (after the Universe has reionized)
Can be used as a (biased) tracer ofthe 3D structure of the Universe HI survey
 HI galaxy redshift survey• The redshifting of HI-line provides the redshift info of galaxies.
• The 3D matter distributions can be reconstructed.

 HI intensity mapping survey [after CD/EoR]• A novel technique to prove the large-scale structure. [Chang+(2010)]• The detection of individual galaxies is not required.
• The integrated HI intensity of several galaxies in one pixel is measured.

 HI intensity mapping survey [during CD/EoR]• Measure the large-scale distributions of the HI inside the IGM via
the brightness temperature.

 Radio continuum survey• Measure galaxy synchrotron radiation radio emissions, which is also
treated as a tracer of the large-scale structure.
• In the SKA era, the sufficient number source density will be expected.

Observables

Surveys

HI 21cmline

HI galaxyredshift survey

HI 21cmline

HI intensity
mappingsynchrotronrad.

Radiocontinuum

synchrotronrad.

Weaklensing

optical/IRe.g. Euclid

SKA
Phase

Redshifts

Coverage(deg2)

GalaxynumberPhase-1

z<0.8

5,000~ 107

Phase-2z<230,000~ 109

Phase-1z<3z<3.7

30,00030,000---

30,00030,0005,000~ 108~ 109

Phase-1z<6z<6z<33 [arcmin-2]

Phase-2z<630,000

10 [arcmin-2]

z<215,000~ 108

Phase-2

Phase-1
Phase-2

Δν/ν = 0.3 @ 0.8-1.7[GHz], Δθ = 1 [arcsec], tint = 104 [hour]

Observables

Surveys

HI 21cmline

HI galaxyredshift survey

HI 21cmline

HI intensity
mappingSKA
Phase

Redshifts

Coverage(deg2)

GalaxynumberPhase-1z<0.8

5,000~ 107

Phase-2z<230,000~ 109

Phase-1z<3z<3.730,000
30,000---Phase-2

Phase-1z<630,000
Radiosynchrotron
continuum
Phase-2
rad.
z<630,000
Phase-1
Even phase-1
RC surveys
z<3will cover
5,000
Weak IM andsynchrotron
thelensing
extremely Phase-2
large surveyz<6volume30,000
rad.
(available full sky out to very high-z)!
optical/IRe.g. Euclid

z<215,000

~ 108
~ 109
3 [arcmin-2]
10 [arcmin-2]~ 108

Δν/ν = 0.3 @ 0.8-1.7[GHz], Δθ = 1 [arcsec], tint = 104 [hour]When the Phase-2 is constructed, the flux threshold will
be drastically improved
the spectropic
SKA (~5μJy), providing
Coverage
GalaxyObservables
SurveysRedshifts2)
PhaseHI galaxies can be(degnumber
survey of 1 billion
delivered.
7
Phase-1
z<0.85,000~
10HI galaxy
HI 21cmline

redshift survey

Phase-2z<230,000~ 109

HI 21cmline

HI intensity
mappingPhase-1z<3z<3.7

30,00030,000---30,00030,0005,000~ 108~ 109

Phase-1z<6z<6z<3

3 [arcmin-2]

Phase-2z<630,000

10 [arcmin-2]

z<215,000~ 108

synchrotronrad.

Radiocontinuum

synchrotronrad.

Weaklensingoptical/IRe.g. Euclid

Phase-2

Phase-1
Phase-2

Δν/ν = 0.3 @ 0.8-1.7[GHz], Δθ = 1 [arcsec], tint = 104 [hour][Bull+ 1405.1452,SKA Science Book(BAO) (2015)]

BAO with the SKA

図：SDSS

Euclidwave number [1/Mpc]

Pgal(BAO)/Pgal(no BAO)-1

SKA1 (galaxy)

SKA1 (IM)SKA2 (galaxy)

wave number [1/Mpc]

The HI galaxy and IM surveys will provide very accurate measurements
for BAO/RSD of the large scale structure in its both phases.

[Planck XIV(2013), SKA Science Book(BAO) (2015)]

Dark Energy with the SKA
Constraints on dark energy EOS

[Planck XIV(2013), SKA Science Book(BAO) (2015)]

Dark Energy with the SKA
Constraints on dark energy EOS

The SKA1 IM survey will be able to provide competitive
constraints with Euclid, and the SKA2 HI galaxy survey is
expected to allow further improvements.
SKA1 (IM)SKA2 (gal)
SKA1 (gal)

EuclidPlan
1. Introduction

2. Cosmology with the SKA: brief review
3. Cosmology with the SKA
by SKA-JP Cosmology SWG
4. Summary

SKA-JP Cosmology SWG
Cosmological scientific challenges in which we havea deep interest.
 Ultra-large scale cosmology with multitracer technique
D. Yamauchi, S. Yokoyama, K. Takahashi, M. Oguri

 Density perturbations fully remains within the linear regime.
 Baryonic feedback are sufficiently suppressed.
 Clustering analysis is limited due to cosmic variance.

 Exploring the dark Universe with the 21-cm surveys
Y. Oyama, K. Kohri, T. Sekiguchi, H. Shimabukuro, K. Takahashi,
T. Takahashi, S. Yokoyama, K. Yoshikawa
 Redshifted HI 21cm-line  21cm tomography
 In high-z era, nonlinear growth is less effective than that in later era.
 Poor understanding of the astrophysical process during EoRSKA-JP Cosmology SWG
Cosmological scientific challenges in which we havea deep interest.
 Ultra-large scale cosmology with multitracer technique
D. Yamauchi, S. Yokoyama, K. Takahashi, M. Oguri

 Density perturbations fully remains within the linear regime.
 Baryonic feedback are sufficiently suppressed.
 Clustering analysis is limited due to cosmic variance.

 Exploring the dark Universe with the 21-cm surveys
Y. Oyama, K. Kohri, T. Sekiguchi, H. Shimabukuro, K. Takahashi,T. Takahashi, S. Yokoyama, K. Yoshikawa
 Redshifted HI 21cm-line  21cm tomography
 In high-z era, nonlinear growth is less effective than that in later era.
 Poor understanding of the astrophysical process during EOR

A critical test of primordial Universe
One of the most powerful tests of inflation→ Primordial non-Gaussianity= Possible departures from a purely Gaussian
distribution of primordial density fluctuations• Hint about a mechanism for generating
primordial fluctuations• More generally key to understanding theextreme high-energy physics

[SKA Phase 1 Science Priority Outcomes]

A Key Science with SKA1 and SKA2
List of highest priority SKA1 science“Constraints on primordial non-Gaussianity andtests of gravity on super-horizon scales”

Nonlinear parameters : fNL,τNL,gNL,…
Primordial bispectrum (3-pt. fn.)
<Φ(k1)Φ(k2)Φ(k3)> = (2π)3 BΦ(k1,k2,k3) δ3(k1+k2+k3)(amplitude) × (shape dependent fn)

fNL
Primordial trispectrum (4-pt. fn.)
<Φ(k1)Φ(k2)Φ(k3)Φ(k4)> = (2π)3 TΦ(k1,k2,k3) δ3(k1+k2+k3+k4)(amplitude) × (shape dependent fn)

τNL, gNL

PNG consistency relation
All inflationary models predict that (if fNL = 0)
the trispectrum must necessarily exist withτNL≧((6/5)fNL)2[Suyama+Yamaguchi (2010)]

The confirmation of the inequality wouldindicate the presence of complicated dynamics
in the primordial Universe.
It should be the target in future experiments!

PNG in large-scale structure PNG induces the scale dependent-bias such thatthe effect dominates at very large scales:

Pgal = [bL(M,z)+ fNLβf(M,z)/k2D+(z)]2 Pδ
Large PNG
HeavyLight

Galaxy surveys can effectively
constrain PNG to the levelcomparable to CMB.
[Ferremacho+(2014)]

[Seljak (2009), Hamaus+Seljak+Desjacques(2011)]

Multitracer technique The availability of multiple tracers with the different
biases allows significantly improved statistical error inthe measurement of ratio of biases.
All galaxy samples

Ntot, δgal = btot δLight galaxies
Nlδgal,l = bl δHeavy galaxies
Nhδgal,h= bh δσ(ln Pgal) = const. (Ntot→∞)
Limited due to CV!

σ(bh/bl) ~ (Nl-1 + Nh-1)1/2(Nl, Nh→∞)
There is no fundamental limit!

[DY+Takahashi+Oguri 1407.5453,SKA-JP Science Book]

Single-source case : τNL = ((6/5)fNL)2Error on fNL

The constraints of σ(fNL)=O(1) can be obtained even witha single survey. Combining Euclid and SKA, even stronger
constraints of σ(fNL)=O(0.1) can be obtained.

Euclid : photometric survey
SKA : radio continuum survey
Euclid SKA1 Euclid+SKA1 SKA2 Euclid+SKA2

[DY+Takahashi 1509.07585,SKA-JP Science Book]

1σ marginalized contours for fNL, τNL, gNL

τNLgNL

Euclid : photometric survey
SKA : radio continuum survey

fNL

gNL

Complementary information from SKA and Euclid helps tobreak the parameter degeneracy between PNG.

[DY+Takahashi 1509.07585,SKA-JP Science Book]

fiducial τNL

Accessible region: fNL/σ(fNL)>1&τNL/σ(τNL)>1

SKA1
SKA2
SKA2+Euclid

fiducial fNL

[DY+Takahashi 1509.07585,SKA-JP Science Book]

fiducial τNL

Accessible region: fNL/σ(fNL)>1&τNL/σ(τNL)>1(fNL,τNL)～(0.9,8).

fiducial fNL

Summary The SKA will yield transformational science acrossa wide range of cosmology in the next decade.
 Other topics that is of great interests for SKA-JP:
 Precise measurement of primordial fluctuations[Kohri+Oyama+Sekiguchi+T.Takahashi (2013)]

 Constraint properties of neutrino; Σmν, its hierarchy[Oyama+Kohri+Hazumi (2015), Oyama+Shimizu+Kohri (2013)]

 Weak lensing : Synergy between SKA and CMB[Namikawa+DY+Sherwin+Nagata (2015), Saga+DY+Ichiki(2015)]

SKA-Japan Science Book (in English) will appear soon.

Thank you!