ECL 2018 Autumn Workshop Presentation by Prof. Xuelei Chen National Astronomical Observatories, Chinese Academy of Sciences, China

1. Cosmology Research in China
Xuelei Chen
National Astronomical Observatories,
Chinese Academy of Sciences
xuelei@cosmology.bao.ac.cn
ECL Autumn workshop2018
Remote Talk
2018.10.03

2. Outline of my talk
 Introduction
 Major Institutions (Universities & Chinese Academy of Science)
 Existing Facilities and Science Highlights:
 simulations
 optical telescopes (LAMOST)
 radio telescopes (FAST, 21CMA, Tianlai(XC))
 space mission(DAMPE), dark matter search(PandaX) & Cosmic Ray
 Planned Facilities
 AliCPT
 space telescope
 Discovering Sky at Longest wavelength (XC)
 Conclusion

3. Introduction:
Cosmological Problems
• Dark Matter
• Dark Energy
• Origin of the Universe
• Structure Formation
• Observational Probes:
Cosmic microwave background (CMB),
large scale structure (LSS): galaxy
surveys, 21cm,
gravitational lensing,
...

4. Universities
Beijing: Peking Univ. (& KIAA): lensing, quasar; Tsinghua Univ.: galaxy
formation, supernova, reionization, WIMP search; Beijing Normal Univ.:
gravitational wave, Hubble parameter
Shanghai: Shanghai Jiaotong Univ.: large scale structure (simulation,
lensing, galaxy formation, SZ effect and peculiar velocities, ...), WIMP
direct search
Hefei: USTC (theory, optical observation)
Guangzhou: Sun Yatsun Univ.: gravitational wave, dark energy theory
Nanjing: Nanjing Univ.: galaxy formation, dark matter indirect search
Xiamen Univ., Yunnan Univ., ......

5. Chinese Academy of Science
Observatories (running most facilities):
•NAOC(Beijing): dark matter & dark energy, simulation, 21cm cosmology, FAST,
LAMOST, space telescope, + ......
•SHAO(Shanghai): SKA, VLBI
•Purple Moutain Observatory (PMO,Nanjing): Antarctica astronomy, DAMPE, sub-mm
•Yunnan Observatory (Kunming): stellar evolution, solar astronomy
•Xinjiang Observatory (Urumuqi): pulsar, radio astronomy
Other Related Insitiutes:
•Institute of High Energy Physics(IHEP, Beijing): quintom model,CMB(AliCPT), neutrino
experiment, cosmic ray experiment (LHAASO), X-ray space missions
•Institute of Theoretical Physics(ITP, Beijing): theoretical models, gravitational wave
University of Chinese Academy of Science (UCAS)

6. Astronomical Facilities in China
Beijing
Shanghai
Nanjing
Sichuan
Yunnan
Guizhou
Xinjiang
Inner M
ongolia
Tibet
LAMOST
Tianlai
21CMA
FAST
AliCPT
Hefei
Guangzhou

7. Numerical Simulations
Rank Name Rmax
PFLOPS
Vendor year Site
1 Summit 122.3 IBM 2018 Oak Ridge Lab, USA
2 Sunway Taihu
Light
93.015 NRCPC 2016 NSC Wuxi, China
3 Sierra 71.61 IBM 2018 Lawrence Livermore, USA
4 Tianhe-2A 61.445 NUDT 2013 NSC Guangzhou, China
5 Al Bridging
Cloud
Infrastructure
19.88 Fujitsu 2018 NIAIST, Japan
Top 500 List (June 2018)

8. Tiannu
simulation(T.-J.
Zhang, BNU): (3 x
1012
particles), and
new method of
meausuring
neutrino massH. Yu et al., Nature
Astronomy, 1, 0143(2017)
Some Simulation Results
ELUCID (Yipeng Jing, Xiaohu Yang,
SJTU) constrained simulation:
30723
particles, 500 Mpc box
F. Shi et al., ApJ 861, 137 (2018)
L. Gao’s group (NAOC):
work with the MPA and
Durham groups on
simulations (Millenium,
Phoenix, Aquarius, ...)

9. Existing Facilities - Optical TelescopesExisting Facilities - Optical Telescopes
2.16-m Telescope @Xinglong2.4-m Telescope
@Yunnan
60/90cm Schmidt
@Xinglong
100/120cm Schmidt Telescope
@Xuyi (near Nanjing)
Solar Tower @Beijing
Guo Shoujing Telescope (LAMOST)
@Xinglong (near Beijing)
Antarctica 50cm @Dome A

10. LAMOST
focal plane
fiber positioning
Ma: 5.72m×4.4m, Mb: 6.67m×6.05m
Clear aperture: 4m
Field of view: 5°
Number of fibers: 4000
Spectral ranges: 370-900nm
Spectral resolution: R=500, 1000, 1500
Limit magnitude: 20.5m (1.5h, R=500)
Observable sky: -10°to +90° Declination
Originally designed for galaxy survey,
now primarily works on stellar suverys

11. Science Highlights
• Stellar kinematics: Measurement of
Milky Way rotation curve
Vc(R0)=240±6 km/s,
Mh=0.9x10±0.08 x 1012
M⊙
ρlocal= 0.0083±0.0005M⊙pc-3
• Local DM density
ρlocal= 0.018±0.005 M⊙pc-3
=0.68 GeV cm-3
• Puzzling high Li abundance in metal
poor low mass red giants
Y. Huang et. al., 2016, MNRAS 463, 2623
Q. Xia et. al., 2016, MNRAS 458, 3839
H. Li et. al., 2018, ApJL852, 31

12. SDSS eBOSS data –
baryon acoustic oscillation (BAO)
G.-B. Zhao et al., 2017, MNRAS 466, 762
SDSS DR12
Dynamical Dark Energy (3.5σ)?
G.-B. Zhao et al., 2017, Nature
Astronomy, 1,627

13. Existing Facilities - Radio TelescopesExisting Facilities - Radio Telescopes
50m @ Beijing 40m @ Yunnan 25m @ Xinjiang
13.7m Sub-mm
Telescope
Tianma 65
@Shanghai
Solar Radio (MUSER)
40x4.5m + 60x2m
@ Inner Mongolia
FAST 500m @Guizhou 21CMA @Xinjiang
80 stations
Tianlai @Xinjiang
3 x15mx40m cylinder
+ 16 x 6m dish

14. Five-hundred-meter Aperture
Spherical Telescope - FAST
FAST innovation points:
•Unique Karst depression as the site
•Active main reflector
•Cable - parallel robot feed support
FAST Science Cases:
•Neutral Hydrogen line (HI)
survey
• Pulsar research
• Molecular lines
• Joining VLBI network
• Search for Extraterrestrial
Intelligence (SETI)
Construction completed in
September 2016.
So far ~50 pulsars found
during commissioning.

15.  Reflector: R ～ 300m, D ～ 500m, opening
angle: θ ～ 110-120°
 Illuminated aperture: Deff=300m
 Sky coverage: maximum zenith angle 40°
 Working frequencies: 70MHz-3GHz
 Sensitivity 2000 ㎡ /K
 Resolution 2.9’ ，
 Pointing Accuracy ： 8″
 Multibeam 19
Optical Geometry and Specs
A millisecond pulsar found by FAST

16. 21cm Cosmology
• hyperfine splitting of neutral hydrogen
(HI) ground state: 21cm transition
• with redshift of Universe, wavelength
becomes λ=21(1+z)cm
• 21cm tomography: observations over a
frequency range probe 3D structure
• HI: before Epoch of Reionization (EoR),
distributed over whole Universe, after
EoR the gas between galaxies are
ionized by UV photon background, only
within galaxies remain neutral due to
higher recombination rate with high
density
EoR post EoR

17. 21CMA
Total Antennas: 80 x 127(10160)
Baseline 2.74(EW) x 4.01(NS) km
Field of view (NCP) ： 100 sq deg
Angular resolution ： 4’
Frequency coverage ： 70—200 MHz

18. Tianlai (Heavenly Sound)
Pathfinder
• A small pathfinder experiment to
check the basic principles and
designs, find out potential problems
• 3x15x40m cylinders, 96 dual
polarization receiver units
• 16 x 6m dishes
• observe 700-800MHz, can be
tuned in 600-1420MHz
• If successful: expand to full scale
120mx120m, 2500 units
HI intensity mapping

20. Existing Space MissionExisting Space Mission ，， Dark matterDark matter
search and Cosmic Ray Experimentssearch and Cosmic Ray Experiments
Wukong dark matter search
(DAMPE)
Huiyan Hard X-ray (HXMT)
Jinping Underground Lab
(PandaX, CDEX) @Sichuan
Yangbajing Cosmic Ray Experiment
@Tibet

21. The DAMPE e+
e-
spectrum
DAMPE coll., Nature, 552, 63 (2017) H. Jin et al., arxiv:1712.00362
A fit with nearby subhalo DM
annihilations

22. PandaX
J.-P. Cheng et al., arxiv:1801.00587

23. Planned FacilitiesPlanned Facilities
• SVOM(China-France): multi-wavelength (γ+optical) GRB satellite
• Antarctica Observatory (2m optical+ 2m THz)
• LHAASO: 1km2
array cosmic ray experiment (4410m, Sichuan)
• AliCPT: CMB polarization experiment (in Ali, Tibet)
• LOT: 12m optical telescope (candidate sites in Xinjiang, Tibet, and
Sichuan)
• QTT: 110m radio telescope (in Qitai, Xinjiang)
• CSST: 2m space optical telescope (to launch 2023)
• Space gravitational wave experiment (Taiji proposed by CAS, Tianqin
proposed by Sun Yatsen Univ.)
International Cooperation Projects:
• SKA
• TMT

24. AliCPT
• CMB B-mode polarization may indicate
primordial gravitational wave
• AliCPT: collaborating with BICEP, using
site in Ali, Tibet (5250m, 32o
18’ N)
• minimum water vapor (PWV 1mm)
• near town(30km) and airport(20km)

25. AliCPT1:
small aperture (72cm) aim at l~100,
TES bolometer+SQUIDs, 1704*4 detectors,
frequency: 95GHz, 150 GHz
First Light 2020,
observing Mar-Oct.
AliCPT-2: upgrade with 12 more modules
Future:
6000m site (PWV~0.6mm)
2 small aperture covering more frequencies
1 medium aperture(4~6m)

26. Space Telescope
• Part of the Chinese Space Station
Program, 2m optical telescope
• an independently flying module on
the same orbit (not physically
connected to the manned space
station)
• 7 band photometric survey17500
deg2
, iAB =26, galaxies:28/arcmin2
,
• 3 band grism, R~200

27. Ultra-long wavelength satellite array
• Below 10MHz, due to ionosphere
absorption, ground observation is nearly
impossible.
• Dark Age & Cosmic Dawn may produce
feature in 21cm global spectrum, recently
EDGES claim detected such feature
• But ionosphere and RFI may cause
problems
• Far side of Moon provide best
environment for observations
RAE-2 sky map (1979)
Bowman et al., 2018

28. Discovering Sky at Longest (DSL)
wavelength
• Chang’e-4 mission provide opportunity for some
pilot study
• A future dedicated mission: linear array (5-8) of
satellites moving around the moon, take
observation at the backside of the moon, then
transmit data back at the front side of the moon.
• A mother satellite measure the position of the
daughter satellites
• Imaging sky below 30 MHz, and measure all sky
average spectrum with high precision 30-120 MHz
• Currently under intensive study (XC as PI), aim for
mid-2020s launch
Huang et al., arXiv:1805.08259

29. Summary
• China has a wide variaties of ongoing researches in cosmology and
astronomy.
• Some notable theoretical results, e.g. the quintom dark energy model,
holographic dark energy model, Eg test for modified gravity, etc.
• So far most of the data used are from abroad, but new facilities are
beginning to provide interesting results
• Rapid progress in the construction and development of many
astronomical facilities
• Operational support and science research is somewhat inadequate,
partly due to inefficient funding mechanism, partly due to lack of
experienced personnel
• Welcome to International Collaborations, including the Belt & Road
cooperation program

30. I apollogize for those institutes,
projects and people missed in this
talk
Thank You!