GMTNIRS (Giant Magellan Telescope Near-IR Spectrograph) Survey Science Group Workshop 3 조 김상혁 김재영 최나현

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 resolution 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 Coverage1.15 – 2.45 um Beam Diameter16 mm Resolving Power60000 Camera f-ratio13.4 Unit Box80 x 500 x 560 mm Sensor2k x 2k H2RG LM module Wavelength Coverage3.0 – 5.0 um Beam Diameter52 mm Resolving Power Camera f-ratio6.1 Unit Box150 x 474 x 916 mm Sensor4k x 4k H4RG

Off-axis elliptical collimator Volume Phase Holographic Gratings Silicon Immersion Echelle Grating Fig. 1. Optical Layout of JHK module J H K Entrance Slit Off-axis parabolic collimator

Fig. 2. Optical Layout of LM module Silicon Immersion Echelle Grating Reflection Grating Silicon Immersion Echelle Grating Entrance Slit M L Off-axis elliptical collimator Off-axis parabolic collimator

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 methods. Fig.3. Schematic figure of an immersion grating.

Software Fig.4. Electronics and software layout

Summary GMTNIRS will be a key to solve various astrophysical questions and provide a revolution of a spectrograph, particularly 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.