• Publications of The Korean Astronomical Society
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• v.28 no.3
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• pp.75-82
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• 2013

An optical grism for education is fabricated and tested. It is composed of a transmission grating as dispersion element and a prism as diffraction angle compensation device. The transmission grating is Edmundoptics #49-584(spatial frequency 600 lines/mm, dimension $50mm{\times}50mm$). The prism is the fused silica type with angles ($41.3^{\circ}$, $-48.7^{\circ}$, $-90^{\circ}$). The grism device is fabricated by bonding the transmission grating and the prism with an optical adhesive. The zig for assembling the grism, telescope and camera is composed of an aluminum tube, an aluminum disk ring and a T-ring camera adaptor. The fabricated optical grism spectrograph is tested in laboratory using Halogen lamp and Neon lamp with DSLR camera. And the grism assembled with reflector telescope is tested in a field using stellar light. The results show good agreements with design parameters. The wavelength coverage range of the grism is 250 nm at the un-deviated wavelength of 506 nm. The wavelength resolution is 0.11 nm/pixel.

• Journal of Sensor Science and Technology
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• v.26 no.1
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• pp.28-34
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• 2017

An NIR grism Si optical area sensor spectrometer with in-band reference wavelength is designed and fabricated. It is composed of a transmission type diffraction grating (spatial density 300 line/mm), a rectangular N-BK7 prism (apex angle 30 degree), NIR filter(cutoff wavelength 720 nm), an imaging convex lens(focal length 50 mm F1.8) and an IR modified DSLR camera (Canon EOS40D) of Si optical area sensor ($3,888{\times}2,592$ pixels, pixel size $5.710{\mu}m$). "In-band reference wavelength function" is implemented using non-dispersive 0th diffraction order optical beam. The NIR grism spectrometer is tested in a laboratory using a halogen lamp and a Neon lamp. And the spectrometer is used in an astronomy field for obtaining the planet Jupiter NIR spectrum. In-band reference wavelength i.e. un-deviation wavelength is 846 nm, an wavelength resolution is 0.3027 nm/pixel, an wavelength resolving power is 2,794 and an wavelength range is 650~1,000 nm.

• Publications of The Korean Astronomical Society
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• v.32 no.1
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• pp.45-47
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• 2017

The Infrared Camera onboard the AKARI satellite carried out spectroscopic observations with a grism mode named NG, whose wavelength coverage was $2.5-5.0{\mu}m$. We reinvestigate the current flux calibration for the NG grism mode, with which calculated flux density implausibly decreases at $4.9{\mu}m$ especially for red objects due to the second-order light contamination. We perform a new spectral response calibration using blue and red standard objects simultaneously. New response curves which contain both the first-and second-order light are able to separate each contribution consistently and useful for studies of red objects such as CO ro-vibrational absorption in active galactic nuclei.

• The Bulletin of The Korean Astronomical Society
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• v.45 no.1
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• pp.68.1-68.1
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• 2020

외계행성 대기 연구를 위한 투과스펙트럼 관측에 적합한 측분광기를 개발하고 있다. 이 측분광기의 광학적 특성은 380~685nm의 파장범위, FOV 10', R>~400이며, 슬릿부, collimator, VPH grism, imaging lens와 CCD로 구성되어 있는데, 보현산천문대 1.8m 망원경의 CIM(Cassegrain Interface Module)에 카트리지 방식으로 장착되어 사용한다. 그 중 doublet 렌즈 2개를 대칭으로 배치하여 초점거리 280mm가 되도록 만든 collimator는 슬릿을 통과한 f/8 입사광에서 지름 35 mm의 pupil을 만드는데, 이곳에 VPH grism을 설치하였다. collimator 렌즈는 axial spring과 radial spring으로 알루미늄 barrel에 고정하였다. 이 collimator barrel은 CIM에 쉽게 장탈착 할 수 있도록 모듈화 하였다. Collimator Barrel에 대한 구조 해석 결과, 망원경 이동에 따른 중력에 의한 변형은 충분히 작았다. Grism은 슬라이딩 형태로 장착되어 영상 확인도 가능하도록 설계하였다.

• The Bulletin of The Korean Astronomical Society
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• v.42 no.2
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• pp.74.3-74.3
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• 2017

Considering the statistical redshift distribution of the known submillimeter galaxy (SMG) population, most of the significant optical emission lines such as [OII]${\lambda}3727$, $H{\beta}$, [OIII]${\lambda}5007$, and $H{\alpha}$ are redshifted into near-infrared. Using the 3D-HST grism data that provides low resolution NIR spectroscopy over the several deep fields covered by the JCMT large program S2CLS, I investigated the properties of the optical emission lines for submm galaxies which could be used as a proxy for future optical/NIR identification and follow up of the SMGs.

• Journal of The Korean Astronomical Society
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• v.52 no.6
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• pp.235-244
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• 2019

We present the results of near-infrared imaging observations of the galaxy overdensity around the z = 1.44 radio-loud active galactic nucleus (AGN) 6CE1100+3505, which was carried out with the purpose of sampling the redshifted Hα emission from the actively star-forming galaxies that could constitute the overdensity. The existence of the structure around this AGN was spectroscopically confirmed by previous grism observations which are however limited to the central region. Using the CH4Off narrow/medium-band and H broad band filters in the Wide Infrared Camera (WIRCam) on the Canada-France-Hawaii Telescope (CFHT), we constructed a sample of objects that show a flux excess in the CH4Off band due to line emission. The emission line flux is ~ 4.9 × 10^-16 erg s^-1 cm^-2, corresponding to a star formation rate (SFR) of ~ 50 M_⊙ yr^-1 for galaxies at redshifts z ~ 1.4. None of the galaxies with medium-band flux excess is located within 1 Mpc from the central AGN, and there is no evidence that the selected galaxies are associated with the proposed cluster. Along with the star formation quenching near the center that was found from the previous grism observations, the lack of extreme starbursts in the structure suggests that at z ~ 1.4, overdense regions are no longer favorable locations for vigorous star formation.

• Publications of The Korean Astronomical Society
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• v.27 no.4
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• pp.361-362
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• 2012

We summarize the progress on the rest-frame optical spectroscopy of quasars at 3$2.5-5{\mu}m$. This spectral window has been utilized for detecting redshifted $H{\alpha}$ emission lines of our high redshift subsample of quasars. From the calculated emission line widths and luminosities we measured supermassive black hole masses using well calibrated optical mass estimators. Science topics regarding optical based black hole masses at high-z are discussed.

• The Bulletin of The Korean Astronomical Society
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• v.35 no.1
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• pp.78.1-78.1
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• 2010

We present the initial results of rest-frame optical spectroscopy of quasars at 3 < z < 5 from the AKARI space telescope mission program QSONG (Quasar Spectroscopic Observation with NIR Grism). QSONG is an AKARI phase-3 mission program which utilizes the unique capability of spectroscopy at 2.5-5 microns, and is adequate for detecting redshifted Balmer lines. We focus on how to overcome the noise induced from instrumental degradation, and report our measurements of supermassive black hole (SMBH) masses with well calibrated optical mass estimators.

• The Bulletin of The Korean Astronomical Society
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• v.45 no.1
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• pp.69.2-69.2
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• 2020

Korea Astronomy and Space Science Institute (KASI) is developing a coronagraph to measure the coronal electron density, temperature, and speed utilizing spectral change of the K-corona around 400 nm. However, near UV light is more affected by atmospheric effect on the ground than visible light. For the total solar eclipse on July 2 2019, KASI organized an expedition team to test the possibility of the similar measurement scheme in the visible light. The observation site was in Las Flores, San Juan, Argentina. We built an imaging spectrograph using micro lenslet array and grism, named Coronal Integral Field Spectrograph (CorIFS). In addition, images of white light corona, wide field background, and all sky were taken with various camera settings. We present the preliminary results of the expedition.

• Publications of The Korean Astronomical Society
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• v.27 no.4
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• pp.183-184
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• 2012

We present the latest results from the Mission Program NIRLT, the NIR spectroscopic observations of brown dwarfs using the IRC on board AKARI. The near-infrared spectra in the wavelength range between 2.5 and $5.0{\mu}m$ is especially important to study the brown dwarf atmospheres because of the presence of non-blended bands of major molecules, including $CH_4$ at $3.3{\mu}m$, $CO_2$ at $4.2{\mu}m$, CO at $4.6{\mu}m$ and $H_2O$ around $2.7{\mu}m$. Our observations were carried out in the grism-mode resulting in a spectral resolution of ~ 120. In total, 27 sources were observed and 18 good spectra were obtained. We investigate the behavior of three molecular absorption bands, CO, $CH_4$ and $CO_2$, in brown dwarf spectra relative to their spectral types. We find that the $CH_4$ band appears in the spectra of dwarfs later than L5 and CO band is seen in the spectra of all spectral types. $CO_2$ is detected in the spectra of late-L and T type dwarfs.