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Infrared Doppler for the Subaru
telescope: Survey plan and the
current status of the instrument
Takayuki Kotani (NAOJ),
Motohide Tamura, Hiroshi Suto, Jun nishikawa, Bun‘ei Sato, Wak Aoki, Tomonori Usuda,
Takashi Kurokawa, Ken Kashiwagi, Shogo nishiyama, Yuji Ikeda, Donald B. Hall, Klaus W. Hodapp, Shne Jacobson, Jun Hashimoto, Jun-Ichi Morino, Yasushi
Okuyama, Yosuke Tanaka, Shota Suzuki, Jungmi Kwon, Takuya Suenaga, Dehyun Oh, Haruka Baba, Norio Narita, Eiichiro Kokubo, Yutaka Hayano, Hideyuki
Izumiura, Eiji Kambe, Tomoyuki Kudo, Nobuhiko Kusakabe, Masahiro Ikoma Hori, Masashi Omiya, Hidenori Genda, Akihiko Fukui, Yuka Fujii, Olivier Guyon,
Hiroki Harakawa, Masahiko Hayashi, Masahide Hidai, Teruyuki Hirano, Masayuki Kuzuhara, Masahiro Machida, Taro Matsuo, Tetsuya Nagata, Hirohi Onuki,
Masahiro Ogihara, Hideki Takami, Naruhisa Takato, Yasuhiro H.Takahashi, Chihiro Tachinami, Hiroshi Terada, Hajime Kawahara、IRD tem
Next step in Exoplanet science: Understandings of
Earth-like planets in their habitable zone (HZ)
Detection limit of RV survey
Planet mass （MEarth）
10000
1000
Jupiter
Habitable
100
Earth-mass planets around solar type
stars cannot be reached with the currently
available technology
10 Low-mass planets around low mass stars
→
R ad ia l velo city
Earth1
>30MEarth
:
10-30MEarth
3-10MEarth
0.1
0.5-3MEarth
0.01
0.5-5MEarth@HZ :
Tran sit
D irect Im ag in g
M dwarfs
0.2MSun
0.1
Solar type stars
1.0MSun
1
1AU
M icro len sin g
A stro m etry
10
100
Semi-major axis (AU)
Current status of the study of Earth-like planets
0.1-10 Earth Masses or 0.5-2.0 Earth Radii in conservative Habitable zone
 Planets detected by survey
of nearby low-mass stars
 Early K-M dwarfs
 Planet mass > 3.8MEarth
 Planets detected by Kepler
 Follow-up is difficult
 No doppler
measurements (mass is
unknown)
1.
2.
No Earth-like (mass , radius, temperature) planets are detected around
nearby stars
Number of detected habitable planets is not enough for statistical study
Infrared Doppler (IRD) for the Subaru telescope
What is IRD?
• High-resolution, NIR spectrometer for
the Subaru for planet detection by radial
velocity method
• First light will be in the end of 2015, start
of a survey in 2016
Goal of IRD
• Detection of ~ 50 planets around nearby
M dwarfs, including ~10 Earth-like
planets in their habitable zone
Uniqueness of IRD
• One Earth-mass planet in HZ around a lowmass M dwarf (late-type M dwarf) can be
detected
• Late M dwarfs are too faint to observe
with optical/3-meter class IR Doppler
• Wide spectral coverage (J,H,K)
Science goals of IRD
1. Detection of habitabile Earth-like planets
around nearby M dwarfs
Number of Detection
– Minimum Success
• Detection of at least 1, one Earth-mass planet in their
HZ
– Full Success
• Unveiling frequency and properties of habitable Earth
2. Statistical understandings of planet formation
around low-mass stars
– Minimum Success
× >1
× >10
× >25
• 25 > Super-Earth - Jupiter-mass planets around lowmass s stars
– Full Success
• 50> planets including Earth-mass planets
The expected number of planets is estimated by planet population
synthesis and with observing schedule simulation
× >50
2014/11/13
Telescope schedule
Observation Plan
Example of scheduling
• Target stars ～ 100
• Start of survey：2016～
– Other groups will start a survey around 2016,
but mainly for early M dwarfs
• Required observing night
S1?B
IRD
S1?B
IRD
S1?B
IRD
S1?B
IRD
S1?B
IRD
S1?B
IRD
– 170 night （Strategic program)
– Period： 5 years
S1?B
IRD
0.5 night × 7
• Planned schedule:
– 0.5 night × 7/month × 9~10 run/year
– Half night allocation is important to better sample planet orbital period
http://www.naoj.org/cgi-bin/opecenter/schedule.cgi
• Expected number of planets to be discovered:
– Earth-mass planets ：
– Habitable Earth and Super Earths：
~ 28
~10
Total>50
1/1
Instrument development status
Spectral coverage
0.97-1.75 μm
Spectral resolution
70,000 @ 1480nm（3pixel sampling）
Fiber
star + comb, a multi-mode or single-mode fiber
Grating
Echelle & VPH-Grating (order sorting)
RV precision
1 m/s w/ laser frequency comb
Detector
Hawaii 4RG 4096x4096
Cryogenic system
Detector: 60K, Optics: 200K, Pulse-tube cooler
•
•
•
•
•
2010: Project started
2012: Conceptual Design Review
2012-2015： Integration, test of the instruments
End of 2015: First light at the Subaru telescope
2016: Start of a survey
Overview of the IRD instrument
Laser Comb
Mode scrambler
Resolution: R=70000
Wavelength: 0.97-1.75um
Cryo: 60K (detector), 200K (optics)
Star light
From AO
Fiber injection system
(AO bench)
Fiber
(Comb)
Fiber
(star)
spectrometer
Laser frequency comb
(IR Observing floor)
Coudé Room
Spectrometer system
(Coudé room)
Spectrometer Optics
•
•
•
•
Fiber array with 2x MMF+ 2x SMF
F-conversion: F3.33(fiber)→ F12.6 (slit)
Slit: 0.27x2.2”
High blaze angle Echelle grating
Camera system
Hawaii4RG
600mm
VPH Grating
Slit
Collimator
Fibers
F-conversion unit
Echelle grating
(80.7 deg blaze angle, 75um pitch)
1300mm
Ultra Low-CTE ceramic optical bench & optics
Collimator
Flat mirror
600mm
Slit holder
100mm
Optical bench
1300mm
•
•
•
•
Mirror, holder, and optical bench are made of low CTE ceramic (CTE <0.05E-6)
Mirror has good surface roughness (<2nm Ra), surface quality (<λ/4 PV, λ=633nm)
High reflectance after gold coating (>98% from 0.97 to 1.75um)
All components are precisely machined and positioned by suing a 3D coordinate-measuring machine
Ceramic is from Kyocera
Original Laser frequency comb
980nm
• Our original laser frequency comb will cover Y, J, H-band
simultaneously
• Sufficiently wide frequency span(12.5GHz, 0.09nm @ 1.5um)
• Developed by the Tokyo University of Agriculture and Technology
Laser frequency comb spectrum
Full coverage of Y,J,H-band will be achieved soon
Chamber and cryogenic system
Radiation shield covered with MLI
Vibration damper
Ceramic optical bench (~200K)
Kinematic mount/radiation shied base
Pulse-tube cooler
Large format infrared array : Teledyne H4RG15
Under development, Collaboration with IfA, University of Hawaii
Conclusions
 IRD is a NIR high-resolution spectrometer for the Subaru
telescope for very precise RV measurements (~ 1m/s)
 IRD aims at detecting ~50 planets around nearby M
dwarfs, including 10 Earth-like planets in habitable zone
 IRD will survey ~ 100 late M-dwarfs for 5 years and SSP is
planned
 Integration and test of the instruments is ongoing, and a
survey will start in 2016