Summer program introduction in Yunnan university

研究所のサマースクールで使用した研究紹介スライド

1. 宇宙再电离期与21厘米宇宙学
Epoch of Reionization and 21cm
cosmology
©NAOJ
Hayato Shimabukuro[島袋隼士]

2. •Born in Okinawa(冲绳)
•Ph.D from
Nagoya(名古屋) university(2016)
•Postdoc at
Paris observatory(2016-2018)
•Postdoc at
Tsinghua University(2018-2019)
About me

3. •Born in Okinawa(冲绳)
•Ph.D from
Nagoya(名古屋) university(2016)
•Postdoc at
Paris observatory(2016-2018)
•Postdoc at
Tsinghua University(2018-2019)
•Yunnan university（2019-）
About me

4. 现在的宇宙
˜+845

5. 现在的宇宙
恒星、星系 TUBSTHBMBYJFT
˜+845

6. 过去的宇宙

7. 过去的宇宙
没有恒星，星系。黑暗！
宇宙黑暗时代z%BSL"HFT£

8. 过去的宇宙
没有恒星，星系。黑暗！
宇宙黑暗时代z%BSL"HFT£
从黑暗时代到现在的宇宙，宇宙是如何演化的？
)PXEPFTUIFVOJWFSTFFWPMWFGSPNEBSLBHFTUP
DVSSFOUVOJWFSTF

9. Age of the universe
Cosmic microwave background (CMB)

10. Age of the universe
Cosmic microwave background (CMB)

11. Age of the universe
Cosmic microwave background (CMB)

12. Age of the universe
Cosmic microwave background (CMB)
The age of the universe is13.8 Billion years old
(138亿岁)

13. Question
How old are the sun and earth?

14. Question
How old are the sun and earth?
~50亿岁（5 billion years）

15. Question
How old is the milky way galaxy?
(1)50 亿岁
(2)70 亿岁
(3)100 亿岁
(4)130 亿岁

16. Question
How old is the milky way galaxy?
~130亿岁（13 billion years）
(1)50 亿岁
(2)70 亿岁
(3)100 亿岁
(4)130 亿岁

17. Question
How old is the milky way galaxy?
~130亿岁（13 billion years）
HE 1523-0901
(1)50 亿岁
(2)70 亿岁
(3)100 亿岁
(4)130 亿岁

18. •We often use “redshift(红移)” to express distant or past（过去） universe.
Redshift
Redshift
Due to the expansion of the universe, the wavelength of the distant or past universe
extends.
z=
!!!0
!0
Original wavelengthExtended wavelength
z=0: present universe
z=0.1: 1.4 Gyr ago
z=1: 7.8 Gyr ago
z=10: 13.2 Gyr ago
z=20: 13.7 Gyr ago
G:Giga, 10亿年

19. James Webb Space Telescope (JWST)
ALMA
Subaru
Observational frontiers

20. Observational frontiers
•Recently, galaxies at (~3亿岁)
(discovered by JWST) are confirmed
by spectroscopy.
z∼14
Carniani et al (2024)
(Arxiv: 2405.18485)

21. Observational frontiers
Atek et al (2024)
(Arxiv : 2405.21054)
JWST review
Fainter
Star formation rate
Magnitude

22. Observational frontiers
Atek et al (2024)
(Arxiv : 2405.21054)
JWST review
Fainter
JWST has discovered many
high redshift galaxies!
Star formation rate
Magnitude

23. Observational frontiers
Atek et al (2024)
(Arxiv : 2405.21054)
JWST review
Fainter
JWST has discovered many
high redshift galaxies!
Star formation rate
Magnitude

24. Observational frontiers
Atek et al (2024)
(Arxiv : 2405.21054)
JWST review
Fainter
There are more stars than we
expected in the early universe!
JWST has discovered many
high redshift galaxies!
Star formation rate
Magnitude

25. 宇宙历史 (History of the Universe)
现在过去
https://universe-review.ca/
EoR
Dark
Ages
CMB
Big
Bang
宇宙黑暗时代（Dark Ages）~~~ 没有恒星，星系 . ( )z>30?
宇宙再电离期 （Epoch of Reionization, EoR）~~~发光物体的紫外
线光⼦电离中性IGM(星系间媒介) 。 ( )z∼6−15
宇宙黎明 （Cosmic Dawn）~~~第一世代恒星和星系形成 ( )z∼30?

26. 宇宙历史 (History of the Universe)
现在过去
https://universe-review.ca/
EoR
Dark
Ages
CMB
Big
Bang
宇宙黑暗时代（Dark Ages）~~~ 没有恒星，星系 . ( )z>30?
宇宙再电离期 （Epoch of Reionization, EoR）~~~发光物体的紫外
线光⼦电离中性IGM(星系间媒介) 。 ( )z∼6−15
宇宙黎明 （Cosmic Dawn）~~~第一世代恒星和星系形成 ( )z∼30?
These epochs have not
been observed yet

27. ¢$,FOKJ)BTFHBXB¢/BHPZB6OJWFSTJUZ£
Credit: M. Alvarez, R. Kaehler and T.Abel

28. ¢$,FOKJ)BTFHBXB¢/BHPZB6OJWFSTJUZ£
Credit: M. Alvarez, R. Kaehler and T.Abel

29. 我们想知道什么
•最初的恒星和星系如何形成和演化？ (How do first
generation objects form and evolve?)
•第一星系的环境是什么？ What is the environment of
first galaxies?)
•什么时候再电离期开始了？ ?When did reionization
start?）
•再电离的来源是什么 ?（What is source of
reionization?）
…etc

30. How do we explore the dark ages to EoR??

31. How do we explore the dark ages to EoR??
Hydrogen

32. How do we explore the dark ages to EoR??
Hydrogen
Why hydrogen? Because hydrogen is the most abundant
component in the IGM.

33. •21cm line radiation : Neutral hydrogen atom in IGM emits radiation due
to the hyperfine structure.
→ 1.5m or 202 MHz
→ 4.4m or 68MHz
z=6
z=20
Radio wavelength.
(Neutral) hydrogen atom is good tracer for IGM.
21cm line
At redshift , the wavelength of the 21cm line signal becomes mz 0.21(1+z)

34. Brightness temperature
!Tb=
TS!T!
1+z
(1!exp(⌧⌫))
⇠27xH(1 +!m)
✓
H
dvr/dr+H
◆✓
1!
T!
TS
◆✓
1+z
10
0.15
⌦mh
2
◆
1/2✓
⌦bh
2
0.023
◆
[mK]
Red : cosmology Blue : astrophysics
17
•We observe brightness temperature, which is the difference between
spin temperature and CMB temperature

35. Brightness temperature
!Tb=
TS!T!
1+z
(1!exp(⌧⌫))
⇠27xH(1 +!m)
✓
H
dvr/dr+H
◆✓
1!
T!
TS
◆✓
1+z
10
0.15
⌦mh
2
◆
1/2✓
⌦bh
2
0.023
◆
[mK]
Red : cosmology Blue : astrophysics
17
•We observe brightness temperature, which is the difference between
spin temperature and CMB temperature
但是，我们还没有观测EoR和宇宙黎明时
的21cm信号!

36. 21cm line emission
We can map the distribution of HI in the IGM with 21cm
line.
Liu & Shaw (2020)
To describe 21cm signal statistically…
Redshift

37. 21cm line emission
We can map the distribution of HI in the IGM with 21cm
line.
Liu & Shaw (2020)
21cm global signal: Sky-averaged 21cm
line signal
To describe 21cm signal statistically…
Redshift

38. Bouman et al 2018
21cm global signal?
•In 2018, the EDGES group reported the detection of 21cm line global signal. If it’s true,
this is the first detection of the high-redshift 21cm line! But...
Singh’s slide
The reported signal cannot be explained by standard
cosmology and astrophysics!

39. Bouman et al 2018
21cm global signal?
•In 2018, the EDGES group reported the detection of 21cm line global signal. If it’s true,
this is the first detection of the high-redshift 21cm line! But...
Singh’s slide
The reported signal cannot be explained by standard
cosmology and astrophysics!
SARAS3 did not detect signal
（Singh+2022）

40. Bouman et al 2018
21cm global signal?
•In 2018, the EDGES group reported the detection of 21cm line global signal. If it’s true,
this is the first detection of the high-redshift 21cm line! But...
Singh’s slide
The reported signal cannot be explained by standard
cosmology and astrophysics!
SARAS3 did not detect signal
（Singh+2022）
Under debate! Need exotic physics?
mis-calibration? unknown systematics?

41. We can map the distribution of HI in the IGM with 21cm
line.
Redshift
To describe 21cm signal statistically…
Liu & Shaw (2020)
21cm line emission

42. We can map the distribution of HI in the IGM with 21cm
line.
21cm line power spectrum
h!Tb(k)!Tb(k
0
)i=(2⇡)
3
!(k+k
0
)P21
Redshift
To describe 21cm signal statistically…
Liu & Shaw (2020)
21cm line emission

43. HERA collaboration 2022b
Astrophysics from 21cm upper limits
•They obtained some constraints on astrophysical
parameters from 21cm power spectrum upper limits.
•HERA firstly constrains X-ray parameters at high
redshift.
•High redshift galaxies suggest higher X-ray luminosity
and lower metallicity than local galaxies.
Astrophysics with 21cm line signal is
around the corner!?
Shimabukuro+ (2023)

44. HERA collaboration 2022b
Astrophysics from 21cm upper limits
•They obtained some constraints on astrophysical
parameters from 21cm power spectrum upper limits.
•HERA firstly constrains X-ray parameters at high
redshift.
•High redshift galaxies suggest higher X-ray luminosity
and lower metallicity than local galaxies.
Astrophysics with 21cm line signal is
around the corner!?

45. •The construction started in 2022
•The observation is going to start in 2027
22

46. •The construction started in 2022
•The observation is going to start in 2027
22

47. •The construction started in 2022
•The observation is going to start in 2027
22

48. 鸿蒙计划
Go to the moon~~~
Lunar Crater Telescope
“We choose to go to the moon”
-J.F. Kennedy(1962)
FARSIDE

49. How do we extract information from the 21cm line signal?
•21cm power spectrum
•21cm bispectrum
•21cm image map, etc
•Model parameters
•Anything else??

51. Machine learning

52. Artificial Neural Network (ANN)
10
20
30
40
50
60
10 20 30 40 50 60
R
mfp,ANN
[Mpc]
R
mfp,true
[Mpc]
10
20
30
40
50
60
10 20 30 40 50 60
ζ
ANN
ζ
true
1
10
100
1 10 100
T
vir,ANN
[K/10
3
]
T
vir,true
[K/10
3
]
Input ANN
Output
ANN is trained to construct relation
between input and output quantities.

53. Artificial Neural Network (ANN)
10
20
30
40
50
60
10 20 30 40 50 60
R
mfp,ANN
[Mpc]
R
mfp,true
[Mpc]
10
20
30
40
50
60
10 20 30 40 50 60
ζ
ANN
ζ
true
1
10
100
1 10 100
T
vir,ANN
[K/10
3
]
T
vir,true
[K/10
3
]
Input ANN
Output
ANN is trained to construct relation
between input and output quantities.

54. Application of ML to 21cm studies
Hey, ChatGPT, tell me how we can apply ML to 21cm studies.

55. Application of ML to 21cm studies
Hey, ChatGPT, tell me how we can apply ML to 21cm studies.

56. Application of ML to 21cm studies
Hey, ChatGPT, tell me how we can apply ML to 21cm studies.

57. Application of ML to 21cm studies
Hey, ChatGPT, tell me how we can apply ML to 21cm studies.

58. Application of ML to 21cm studies
Hey, ChatGPT, tell me how we can apply ML to 21cm studies.
ANN is often used in the context of 21cm studies

59. •用21厘米森林探索 ,础úgŠExploring fundamental physics with
21cm forest (neutrino, inflation, axion dark matter)
[Shimabukuro et al.(2014), Shimabukuro, Ichiki & Kadota
(2020a,2020c,2023)]
•21cm線统计--21cm statistics (bispectrum, one point statistics)
[Shimabukuro et al.(2015), (2016), (2017a)]
•21cm信号分析与人⼯神经网络21cm signal analysis with artificial
neural network (ANN)
[Shimabukuro & Semelin (2017b), Shimabukuro, Mao & Tan (2022a)]
What I have done

60. ©NAOJ
与我们一起在 SWIFAR 开展
研究!

61. Backup