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.

Software

Fig.4. Electronics and software layout

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.