Constraints on the neutrino mass
by future precise CMB polarization
and 21cm line observations
Yoshihiko Oyama
The Graduate University for Advanced Studies
KEK cosmophysics group
Collaborators
Masashi Hazumi (KEK CMB group)
Kazunori Kohri (KEK cosmophysics group)
◇ Focused experiments
Plancktemperature, E-mode, B-mode
＋
POLARBEAR-2 or Simons Array
E-mode, B-mode
＋
SKA Phase1, Phase2
21cm line brightness temperature（z=7-10）
We studied their sensitivities to constraints
on the sum of the neutrino masses
and the mass hierarchy.
2
◇ Focused experiments
Plancktemperature, E-mode, B-mode
＋
POLARBEAR-2 or Simons Array
E-mode, B-mode
＋
SKA Phase1, Phase2
21cm line brightness temperature（z=7-10）
＋
Baryon Acoustic Oscillation (BAO)
3
contents
1. 21cm line observations
2. Effects of neutrinos on the
growth of the density fluctuations
3. Future constraints on the neutrino
mass by CMB and 21 cm line
4. Summary
4
contents
1. 21cm line observations
2. Effects of neutrinos on the
growth of the density fluctuations
3. Future constraints on the neutrino
mass by CMB and 21 cm line
4. Summary
5
1. 21cm line observations
・Introduction
・21cm line brightness temperature
and the power spectrum
6
◇ 21cm line
21cm line results from hyperfine
splitting of neutral hydrogen.
1S state
𝝀 = 𝟐𝟏cm
𝝂21 = 𝟏. 𝟒𝟐𝐆𝐇𝐳
Spin =1
triplet
proton
electron
Spin =0
singlet
𝜟𝑬 = 𝟓. 𝟖 × 𝟏𝟎−𝟔 eV
7
◇ Cosmological 21 cm radiation
S.G. Djorgovski et al. &
Digital Media Center, Caltech.
CMB
z~1000
Dark age
Cosmic dawn
15 ≲ z ≲ 30
(The late stage of the dark age)
The epoch of reionization
6 ≲ z ≲ 15
We particularly focused on
the epoch of reionization ( 7 ≲ z ≲ 10 )
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◇ 21cm line and cosmology
𝝀𝟐𝟏 = 21 cm
𝑇21cm
This signal has information of the
matter distribution.
We can constrain cosmological
parameters (e.g. ΩCDM .)
M.McQuinn, O.Zahn, M.Zaldarriaga, L.Hernquist, S.R. Furlanetto
(2006) Astrophys.J.653:815-830,2006
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◇ Advantages of
21 cm line observations
Z=0
linear
non linear
𝑘 [ℎ Mpc −1 ]
𝑃(𝑘) [ℎ−3 Mpc 3 ]
𝑃(𝑘) [ℎ−3 Mpc 3 ]
１. Non-linear effects are small
Z=3
linear
non linear
𝑘 [ℎ Mpc −1 ]
２. Broad redshift range
・ A lot of independent Fourier modes.
・ The time evolution of the density fluctuations
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1. 21cm line observations
・Introduction
・21cm line brightness temperature
and the power spectrum
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◇ Brightness temperature 𝑇𝑏
𝑇𝑏
𝜈21
, 𝒓, 𝑧 ≈ 27𝑥HI 1 + 𝛿𝑏
1+𝑧
Ω𝑏 ℎ 2
0.023
𝑇𝛾
Fluctuation of baryon × 1 − 𝑇𝑆
0.15 1 + 𝑧
Ω𝑚 ℎ2 10
1
2
𝐻(𝑧)/(1 + 𝑧)
𝑑𝑣|| /𝑑𝑟||
1. Peculiar velocity of gas
2. Expansion of universe
𝑻𝑺 : Spin temp
𝑻𝜸 : CMB temp
𝑥HI : Neutral fraction
𝑻𝑺 > 𝑻𝜸
emission（6 ≲ z ≲ 15）
𝑻𝑺 < 𝑻𝜸
absorption（15 ≲ z ）
12
contents
1. 21cm line observations
2. Effects of neutrinos on the
growth of the density fluctuations
3. Future constraints on the neutrino
mass by CMB and 21 cm line
4. Summary
13
◇ Effects of neutrinos on the growth of
the density fluctuations
𝝂
~ Horizon scale
When neutrinos are
relativistic 𝒎𝝂 𝒄𝟐 ≪ 𝒌𝑩 𝑻 ,
neutrinos run up to
the horizon scale
(Free-streaming)
This effect erases their own
fluctuations within such scales.
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Matter power spectrum
𝒁=𝟎
𝑷 𝒌 = 𝜹𝒌
𝟐
The free-streaming
effects of neutrinos
Heavier
neutrino mass
This suppression
becomes larger.
Total mass Σ𝑚𝜈 = 𝑚1 + 𝑚2 + 𝑚3
15
Polarization of CMB
Power spectra of CMB polarization
(lensing B-mode 𝑪𝑩𝑩
𝒍 )
The free-streaming
effects of neutrinos
By observation of
CMB polarization,
we can constrain
the neutrino mass.
Total mass Σ𝑚𝜈 = 𝑚1 + 𝑚2 + 𝑚3
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◇ Current neutrino mass constraints
WMAP 9-year + ACT + SPT + BAO + H0
・𝛴𝑚𝜈 : sum of the neutrino masses
𝛴𝑚𝜈 < 0.44 eV (95%CL)
・𝑁𝜈 : neutrino number of species
𝑁𝜈 = 3.84 ± 0.40 (68%CL)
Planck (temperature) + WMAP polarizations
＋ ACT + SPT + BAO
𝛴𝑚𝜈 < 0.28 eV (95% C.L), 𝑁𝜈 = 3.32+0.54
−0.52
17
contents
1. 21cm line observations
2. Effects of neutrinos on the
growth of the density fluctuations
3. Future constraints on the neutrino
mass by CMB and 21 cm line
4. Summary
18
◆ CMB, 21cm, BAO観測実験
19
◇ CMB polarization experiments
◆ POLARBEAR-2
95, 150 GHz
◆ Simons Array
POLARBEAR-2 × 3
95, 150, 220 GHz
KEK CMB group is developing these experiments.
We took account of combinations of
above 2 experiments and Planck satellite.
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◇ 21cm line experiment
◆ SKA (Square kilometer Array)
SKA low frequency
(Australia)
Construction of Phase1
will start in 2018.
http://www.skatelescope.org/
We took account of Phase1 and Phase2
(Phase2 has 10 times larger collecting area.)
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◇ BAO Observation
◆ Dark Energy Spectroscopic
Instrument (DESI)
・Galaxy survey
(2018年から観測開始)
Redshift range :
0.1 < 𝑧 < 1.9
Survey solid angle :
14000 square degree
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◆ Constraints on the sum of the
neutrino masses 𝚺𝒎𝝂 and
neutrino number of species 𝑵𝝂
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◆ Constraints on neutrino number of
species 𝑵𝝂
95% C.L. Contour, 𝜮𝒎𝝂 = 𝟎. 𝟏eV
CMB + DESI (BAO)
90% C.L
Simons Array
+ DESI
+ 21cm line
90
%
C.L
CMB+DESI
+SKA
By Planck + Simons Array + SKA,
the neutrino total mass is detectable at 95%C.L.
◆ With residual foregrounds
Motivation:
How much is it necessary to
remove foregrounds?
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◆ Constraints on neutrino number of
species 𝑵𝝂 with residual foregrounds
95% C.L. Contour, 𝜮𝒎𝝂 = 𝟎. 𝟏eV
CMB + DESI (BAO)
90% C.L
Simons Array
+ DESI
+ 21cm line
90
%
C.L
CMB+DESI
+SKA
Because constraints from CMB become weaker,
combinations of CMB and SKA is more important.
◆ Constraints on the neutrino
mass hierarchy
27
◇ The neutrino mass hierarchy
Normal hierarchy
𝒎𝟑 ≫ 𝒎𝟐 > 𝒎𝟏
𝒎𝟑
𝛥𝑚23
𝛥𝑚12
𝒎𝟐
𝒎𝟏
Σ𝑚𝜈 ≳ 0.05 eV
𝒎𝝂 𝒄 𝟐 ≫ 𝒌 𝑩 𝑻
Inverted hierarchy
𝒎𝟐 > 𝒎𝟏 ≫ 𝒎𝟑
𝛥𝑚12
𝒎𝟐
𝒎𝟏
𝛥𝑚23
𝒎𝟑
Σ𝑚𝜈 ≳ 0.1eV
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◇ Effects of the mass hierarchy
Ratios of matter power spectra (at z = 8)
𝑷𝑵𝑯 Normal
𝑷𝑰𝑯 Inverted
Σ𝑚𝜈 becomes smaller
The differences due to
the mass hierarchy
larger
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◆ Parameterization of the mass hierarchy
𝒎𝟑 − 𝒎𝟏
𝒓𝝂 ≡
𝜮𝒎𝝂
T. Jimenez, T. Kitching, C. Pena-Garay,
L. Verde, JCAP 1005:035,2010
Normal 𝒓𝝂 > 𝟎
Inverted 𝒓𝝂 < 𝟎
Behaviors of 𝒓𝝂
Dotted lines express
allowed regions by
oscillation experiments
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◆ Contours of 95% C.L. forecasts
in 𝒓𝝂 -𝜮𝒎𝝂 plane
Normal hierarchy
Inverted hierarchy
SKA2
CMB+DESI
+SKA1
CMB+DESI
+SKA1
SKA2
In the inverted case, SKA phase1 + Simons
Array + Planck has enough sensitivity to
31
determine the mass hierarchy.
◆ Contours of 95% C.L. forecasts
in 𝒓𝝂 -𝜮𝒎𝝂 plane
Normal hierarchy
Inverted hierarchy
SKA2
CMB+DESI
+SKA1
CMB+DESI
+SKA1
SKA2
In the inverted case, SKA phase1 + Simons
Array + Planck has enough sensitivity to
32
determine the mass hierarchy.
◆ Contours of 95% C.L. forecasts
in 𝒓𝝂 -𝜮𝒎𝝂 plane with residual foregrounds
Normal hierarchy
Inverted hierarchy
SKA2
CMB+DESI
+SKA1
CMB+DESI
+SKA1
SKA2
In the inverted case, SKA phase2 + Simons
Array + Planck has enough sensitivity to
33
determine the mass hierarchy.
◆ Contours of 95% C.L. forecasts
in 𝒓𝝂 -𝜮𝒎𝝂 plane with residual foregrounds
Normal hierarchy
Inverted hierarchy
SKA2
CMB+DESI
+SKA1
CMB+DESI
+SKA1
SKA2
In the normal case, SKA phase2 + Simons
Array + Planck has enough sensitivity to
determine the mass hierarchy.
34
contents
1. 21cm line observations
2. Effects of neutrinos on the
growth of the density fluctuations
3. Future constraints on the neutrino
mass by CMB and 21 cm line
4. Summary
35
5. Summary
■ We studied sensitivities of 21cm line (SKA)
+ CMB polarization observations
(POLARBEAR-2, Simons Array) to the
neutrino total mass.
■ Planck + Simons Array + SKA phase1
can detect the neutrino total mass at 2σ
(if 𝚺𝒎𝝂 ~𝟎. 𝟏eV.)
■ Planck + Simons Array + SKA may
determine the neutrino mass hierarchy.
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