2019/05/29 East Asia SKA Science Workshop @Shanghai Astronomical Observatory

Cosmology andDark Energy withfuture HI galaxy surveys
Daisuke Yamauchi
Kanagawa University

Cosmological observables➢Cosmic Microwave Background→ radio
CMB temperature map◆ Baryon Acoustic Oscillation◆ Redshift-Space Distortion◆ Gravitational Lensing→ optical + Radio (New!)
complementaryLine-of-sight [Mpc/h]➢Large-Scale Structure

Redshift-Space Distortion[SDSS-III BOSS]

Lineofsight

Angular direction [Mpc/h]Why “radio” frequency?
◆Hyperfine transition radiation of neutral hydrogen：21cm line
wavelength λ = 21 cm( ν=1.4GHz : radio freq )

pe

1S

p

5.9×10-6eV

Hyperfine structuree

Why “radio” frequency?
21cm lineobservation

traces spatial distribution ofIGM/galaxies indark age/structure formation= Information of growth!

Dark AgeHI mainly lives
in IGM.

Formation epoch
HI mainly lives
in galaxies.

SKA Science Book/Red Book
◆ SKA Science Book [2015]

https://www.skatelescope.org/books/

135 Chapters, 1200 Contributors, 2000 Pages!
◆ Red Book
[Bacon+DY+(2018)]

Contributions fromJapanese community➢ SKA-Japan Consortium◆ SKA-Japan SKA Science Book[2015, in Japanese(sorry!)]◆ Review (in English) [DY+(2016)]

http://ska-jp.org/ws2015/SKA-JP/talks/SKAJP_Science_Book_2015.pdf

SKA-Japan

SKA-Japan Cosmology SWG
D. Yamauchi (Kanagawa, Chair)
R. Ando (Nagoya)→ today’s talk!
K. Ichiki （Nagoya）
K. Kohri (KEK, Sokendai)
T. Minoda (Nagoya)
A. Nishizawa (Nagoya)
S. Saga (Kyoto)
T. Sekiguchi (Tokyo)
H. Shimabukuro (Tsinghua) → today’s talk!
K. Takahashi (Kumamoto) → tomorrow’s talk!
T. Takahashi (Saga)
S. Tanaka (Kumamoto)→ today’s talk!
S. Yokoyama (Nagoya)
K. Yoshikawa (Tsukuba)
S. Yoshiura (Melbourne)Brief review ofSKA Cosmological Surveys

➢ HI [21-cm] line survey◆ The redshifting of HI-line provides the redshift information.

✓ HI galaxy redshift survey• The 3D matter distributions can be reconstructed.
• Measure the peculiar velocity field → info on how structure grows.

✓ Mid-freq HI intensity mapping [after CD/EoR]• The detection of individual galaxies is NOT required.
• The integrated HI intensity of several galaxies in one pixel is measured.

✓ Low-freq HI intensity mapping [before CD/EoR]• Measure the large-scale distributions of the HI inside the IGM via
the brightness temperature.

➢ Radio continuum survey• Measures galaxy synchrotron radiation radio emissions, which isadvantageous in detecting high-z galaxies.
• Provides a featureless spectrum → The redshift info is not available.

SKA
Phase

redshiftSky
coverage

GalaxynumberPhase-1

z<0.8

1/8

~ 107

(gal)

Phase-2

z<2

3/4

~ 109

HI
[21cm line]

HI intensity
mapping survey(MID-IM)

Phase-1z<3z<3.7

3/4
3/4---HI[21cm line]

HI intensity
mapping survey(LOW-IM)

Phase-1

3<z<273<z<27

1/40
3/4

---Synchrotron
radiation

Continuumsurvey(conti)Phase-1z<6z<63/4
3/4~ 108~ 109

Opticale.g. Euclid

z<2

3/8

~ 108

ObservableHI[21cm line]

SurveyHI galaxy
surveyPhase-2

Phase-2

Phase-2

S = 70(SKA1gal), 5(SKA2gal), 1(SKA1cont), 0.1(SKA2cont) [μJy]Δθ = 1(SKA1), 0.1(SKA2) [arcsec], tint = 104 [hr]SKASkyredshiftcoverage
Even phase-1 IM and Phase
RC surveys will coverObservable

Surveygalaxy large
Phase-1
the HI
extremely
survey volumez<0.8HIsurvey
full sky Phase-2
out to very high-z)!
[21cm line] (availablez<2(gal)HI[21cm line]

HI intensity
mapping survey(MID-IM)

Phase-1

HI[21cm line]

HI intensity
mapping survey(LOW-IM)

Phase-1

Synchrotron
radiation

Continuumsurvey(conti)Phase-1

Opticale.g. Euclid

Phase-2

Phase-2

Phase-2

Galaxynumber

1/8

~ 107

3/4

~ 109

z<3z<3.7

3/4
3/4

---

3<z<273<z<27

1/40
3/4

---

z<6z<63/43/4~ 108~ 109z<2

3/8~ 108

S = 70(SKA1gal), 5(SKA2gal), 1(SKA1cont), 0.1(SKA2cont) [μJy]Δθ = 1(SKA1), 0.1(SKA2) [arcsec], tint = 104 [hr]When the Phase-2 is constructed, the flux threshold will
be drastically improved
the spectropic
SKA (~5μJy), providing
Sky
GalaxyObservable
Surveyredshiftsurvey of 1 billion(!) HI galaxies canbe delivered.
Phasecoverage
number7
HI galaxyPhase-1z<0.8
1/8~10HI[21cm line]

survey(gal)Phase-2z<2

3/4~ 109HI[21cm line]HI intensity
mapping survey(MID-IM)

Phase-1z<3z<3.7

3/4
3/4---

HI[21cm line]

HI intensity
mapping survey(LOW-IM)

Phase-1

3<z<273<z<27

1/40
3/4

---

Synchrotron
radiation

Continuum
survey(conti)Phase-1z<6z<63/4
3/4

~ 108
~ 109

Opticale.g. Euclid

z<2

3/8~ 108

Phase-2

Phase-2

Phase-2

S = 70(SKA1gal), 5(SKA2gal), 1(SKA1cont), 0.1(SKA2cont) [μJy]Δθ = 1(SKA1), 0.1(SKA2) [arcsec], tint = 104 [hr]

[SKA Phase 1 Science Priority Outcomes]A Key Science with SKA➢List of highest priority SKA1 science“Constraints on primordial non-Gaussianity andtests of gravity on super-horizon scales”＝ “Inflation & Dark Energy”

Cosmology and Dark Energy
with HI galaxy surveys

How do we characterize Dark Energy?
◆Expansion history

Equation-of-state◆Fluctuation of galaxy number count: δ=δn/n
Growth index

[Planck XIV(2013)]

Dark Energy Equation-of-State

CosmologicalConstant[Planck XIV(2013), SKA Science Book(BAO) (2015), Bull (2016)]

Dark Energy Equation-of-StateThe SKA1 MID-IM survey will be able to provide
comparable constraints with e.g. Euclid, and the SKA2 HI
galaxy survey is expected to allow further improvements.
SKA1(MID-IM[B1])
SKA1(MID-IM[B2])
BOSS[current]
SKA2(gal)SKA-Japan[Planck XIV(2013), Kohri+Oyama+Sekiguchi+T.Takahashi(2016)]

Dark Energy Equation-of-State

SKA1(LOW-IM)
SKA2(LOW-IM)+Planck+BAO+Sne+H0+Planck+BAO+SNe+H0

Since LOW IM survey probes different redshift epoch
compared with other observables, the constraining
power improves significantly (if we can reduce theforeground)!*Note : the collaboration with EoR/CD SWG is essential!]

[Kohri+Oyama+Sekiguchi+T.Takahashi(2016)]

SKA-Japan

DE EoS z-dependence from LOW-IM◆ The z-dependence of EoS is highly model-dependent.
◆ SKA constrains the model in which the EoS changes at high-z.

SKA(LOW-IM)

SKA(LOW-IM)+Planck+BAO+SNe+H0+Planck+BAO+Sne+H0[Bull(2016), SKA Science Book(RSD) (2015)]

Growth index and Dark Energy◆ can trace the (linear) growth history.
◆ can distinguish and hopefully exclude the dark energy models.

Growth index

DGP braneworld
GR
Massive gravity
f(R) gravity
KGB gravity
Equation-of-state[Bull(2016), SKA Science Book(RSD) (2015)]

Growth index and Dark Energy◆ can trace the (linear) growth history.
◆ can distinguish and hopefully exclude the dark energy models.

Growth index

SKA1(LOW-IM)

SKA1(MID-IM[B1])
SKA2 (gal)SKA1(MID-IM[B2])BOSS

Equation-of-state[DY+Yokoyama+Tashiro (2017)]

SKA-Japan

Nonlinear Growth and Dark Energy◆ Even if wDE=-1 and γ=γGR, it is NOT necessary that our Universe
is described by ΛCDM with GR.
◆ Non-Gaussianity should be generated from nonlinear growth.

SKA1(gal)

2nd order index

SKA2 (gal)nKGB

EuclidHorndeski(wDE=-1, γ=γGR)

Growth index

2nd order index
can carry new info thatis not included in thelinear-order!

SKA-Japan

Dark Energy and Scalar-Tensor Theories
 Scalar-Tensor Theories have been widely studied as analternative to the dark energy.

 GW170817+GRB 170817A gave the stringent constraint on
the speed of GW : |cGW/cEM-1|<10-15, which rules out theories
which predict a variable GW speed.
The most general framework that has been developed so far[Langlois+Saito+DY+Noui (2018)]

[Hirano+Kobayashi+DY+Yokoyama (2019)]

SKA-Japan

Growth index and Scalar-Tensor Theories“GLPV” parameter αH/(1-Ωm)◆ The precise measurement of growth of structure can provide
the severe constraint on the wide class of modified gravity.
We hunt down dark energy model by
combining this with local constraint!

BOSS:|γ-6/11|<0.1
SKA :|γ-6/11|<0.007“DHOST” parameter β1/(1-Ωm)[Gray(stellar structure):
Kobayashi+DY+(2015),
Saito+DY+(2015),Sakstein+(2015) ]Summary➢ The SKA will provide new information of DE andhopefully single out the true model of DE.
➢ Other topics :Various Synergies

 With CMB observations：Delensing[Namikawa+DY+Sherwin+Nagata (2015)]

 With optical galaxy surveys：Multitracer[DY+ (2014), DY+K.Takahashi(2015), DY+Yokoyama+K.Takahashi(2016)]

 With particle physics：Lepton asymmetry, ν,…
[Kohri+Oyama+Sekiguchi+T.Takahashi (2014),…]Thank you!