GMTNIRS(Giant Magellan Telescope Near-IR Spectro-
graph)
Survey Science Group Workshop
3 조김상혁 김재영 최나현
2013.02.15
Index
• Concept of GMTNIRS
• Specification of GMTNIRS
• Silicon immersion grating
• Software
• Summary
Concepts of GMTNIRS
• GMTNIRS will perform unique and substantial studies of many aspects of stars and planets using their high resolu-tion Near-IR spectroscopy.
• Science areas– The physical picture of YSOs(Young Stellar Objects)
• Fundamental stellar properties• Radial velocity• Magnetic field strength
– The chemistry and structure of protoplanetary disks– Planet formation
• Discoveries of Jupiter and Saturn-mass objects orbiting brown dwarfs• Disk instabilities• Core accretions
– Chemical evolution of the AGB and RGB stars• The structure of their photospheres• The mass loss rates
Specification of GMTNIRS
• Instrument concept– The short wavelength (JHK) module– The long wavelength (LM) module– Adaptive optics system
JHK module
Wavelength Coverage 1.15 – 2.45 um
Beam Diameter 16 mm
Resolving Power 60000
Camera f-ratio 13.4
Unit Box 80 x 500 x 560 mm
Sensor 2k x 2k H2RG
LM module
Wavelength Cover-age
3.0 – 5.0 um
Beam Diameter 52 mm
Resolving Power 100000
Camera f-ratio 6.1
Unit Box 150 x 474 x 916 mm
Sensor 4k x 4k H4RG
Off-axis elliptical collima-tor
Volume Phase Holographic Grat-ings
Silicon Immersion Echelle Grating
Fig. 1. Optical Layout of JHK module
J
H
K
Entrance Slit
Off-axis parabolic collima-tor
Fig. 2. Optical Layout of LM module
Silicon Immersion Echelle Grating
Reflection Grating
Silicon Immersion Echelle Grating
Entrance Slit
ML
Off-axis elliptical collima-tor
Off-axis parabolic collima-tor
Silicon Immersion Gratings
• Prism-shaped reflection grating• The high refractive index (n=3.4) of silicon
– Keep the high spectral resolution with a much smaller beam size.
• Silicon lithography– enables continuous spectral coverage.– coarse gratings can be fabricated by silicon lithographic meth-
ods.
Fig.3. Schematic figure of an immersion grat-ing.
Summary
• GMTNIRS will be a key to solve various astrophysical ques-tions and provide a revolution of a spectrograph, particu-larly in wavelength coverage.
• GMTNIRS will use relatively well developed technologies, but the outcome will give a significant achievement in the IR spectroscopy.
• GMTNIRS will improve the grating quality to be compact and robust by using silicon immersion gratings.