SPIE 2012 8446-152

First light observation of GIGMICS( ermanium mmersionratingid- nfrared ryogenic pectrograph)

by Kanata 1.5-m telescope at Higashi-Hiroshima Observatory
Yasuhiro HIRAHARA (Nagoya University), yasu@nagoya-u.jp, & GIGMICS team:
Yoshio TATAMITANI, Keishin AOKI, Kanako OTA, Sho SHIBATA,
Tsuyoshi HIRAO, Noboru EBIZUKA(Nagoya University)
Michitoshi YOSHIDA, Koji KAWABATA, Makoto UEMURA, Takashi OOSUGI(Hiroshima Univ.)
Ryuji FUJIMORI, Hiroki OHIWA, Hisayuki NAGAHIRO, Kentarou KAWAGUCHI(OkayamaUniv.)
Abstract: We have developed a germanium immersion grating mid-infrared cryogenic spectrograph (GIGMICS) designed for the Nasmyth focus stage of NAOJ
Subaru 8.2-m telescope, which operates at N-band (8-13 μm) in wavelength (λ) with maximum resolving power R（≡λ/Δλ） ~ 50,000. A single crystal germaniumechelle immersion grating (30 × 30 × 72 mm) for collimated beam size of 28 mmφ was fabricated by utilizing ultra precision micro-grinding method coupled with theELID (ELectrolytic In-process Dressing) technique (Ohmori, H. 1992, Ebizuka et al. 2003). After the critical test for the application to the laboratory gas-phase IR
high-resolution spectroscopy(Hirahara et al. 2010), we have conducted the “first light” astronomical observation of GIGMICS by the Kanata 1.5-m telescope at
Higashi-Hiroshima Observatory from Jan. to Apr., 2011. Toward many astronomical objects such as the Moon, Venus, Jupiter, circumstellar envelopes of late-typestars, proto-planetary nebulae, and interstellar molecular clouds in the vicinity of star-forming regions, we conducted spectroscopic observations in the N-band region.
Importance of Mid-IR High-resolution Observations

I: Scientific Objective
Atmospheric Transmission at Mauna Kea(R~10,000)

Transmittance (%)

100

C3H3+, CH3+

C3H3+80

C6H6C6H2

CH3+60

C4H2

H3+40
20

H2CO2N-band

COH2O
246

H2

CO2O3
81012

Wavelength/μ m

141618

III: First Light Observation

Chemistry:• All molecules have vibrational transitions, especially for “non-polar” molecules & ions.
• Mid-IR region is a “Fingerprint Region” for Organic Compounds.
• High-resolution ro-vibration spectra make definite identification for gas phase species.
Astronomy:• N-band is an “open window” to the atmosphere.
• High-resolution observations of interstellar molecules give information for kinematics.
→So far, Only 〜30 molecular species have been identified in IR
Cf: In the radio wavelength region, >140 species identified.

↓This study: A breakthrough for the development of high-sensitive and high20 resolution spectrometer for the N-band, especially for the detailed line survey
observations, searching for the new interstellar molecules.

II: Development of GIGMICS“Kanata”: ”Higashi-Hiroshima Observatory,Hiroshima Astrophysical Science Center
Hiroshima University 1.5-m telescope“Key device” : Immersion Grating: is --••Diffraction grating with refractive index n>1
material in the optical path.
Because of the large optical path difference, thesize of the spectrograph can be effectively reducedby 1/n for the same R=λ/Δλ=ΔL/λL

L
nDL=2L

Conventional Grating

n=Subaru IR Simulator of NAOJ.
height 503m

LDL=2nLImmersion GratingThis study: First fabrication of Germanium (n=4.0)• Surface Roughness:11.5 nm rms Immersion Grating by RIKEN’s ELID (ELectrolytic• decrease of R by wavefront error: In process Dressing) Micro-machining Method
73 % => real R~38,000(Ebizuka et al., 2003).

GIGMIGS on Nasmyth Stage of “Kanata”
Jan-Apr of 2011

IV: Result: (I) Full N-band Echelle Spectrograph toward the Moon Total pixels: 412 x 4260, Identified diffraction order: 330-565
Observation• Date: Apr. 4, 9, 10, 13,14, 16 2011
• Method: ON/OFF• Integration time: <50secs.
• Mosaics of 8 echellegrams• In total, 377 telluric lines are assigned
to CO2, H2O, O3, and N2O• Definite assignment of diffraction order

λ=8.0 μmN2O

λ=8.5 μm

N2O

FSR=0.0145 μm

H2O

H2O(R-branch)

CO2(P-branch)

V: Result: (II) Mapping observation of [S IV] in NGC7027

VI: Result: (III) Detection of new CO2 transition in Venus

The planetary nebula NGC7027 is one of
the most famous stellar object. It has HII
region near the central star, and also
expanding molecular cloud in the outerenvelope. The [S IV] emission is detectedby the ISO SWS observation.

Venus, the second planet of the solarsystem, is similar to Earth in termsof size and mass. However, theatmospheric composition and thestructure are significantly different.
Above all, the atmosphere of Venus
is composed dominantly of CO2.

Baseline subtracted Spectrum of [S IV]

Detection of [S IV] on the echellegram

Energy level diagram of Sulfur

Detection of strong [S IV] forbidden emission line
(2P3/2→2P1/2: M1) originated from HII region of NGC7027.

[S IV]First detection of 11 lines !
Detection of (c), (d) transitions reflects
high temperature and CO2 abundance ofVenusian atmosphere.

Vibrational Energy Level
Diagram of CO210.1215 μm

AtmosphericCO20.10 l.y.

Severe effect of time variation of “Sky”
for the N-band in the observatory site =>• “Psudo-emission” of the telluric CO2• Irregular intensity: line vs. thermal
Background component

Observation• Date: Apr. 2, 6, 10, 13 2011
• LST : AM 5:30 ~ 6:00
• Wavelength: 8.0 ~ 10.8 μm• Integration time: 200 seconds• Point : center of Venus• detected from Venus solely(c) 12CO2 (ν3+ν2) ← (ν1+ν2)(d) 13CO2 ν3 ← ν1

Spatial distribution of [S IV]

Result• [S IV] is spread about 0.10 light years
in the southwestern area of NGC7027.
• The observed wavelength of [S IV]:
λcenter=10.51185 (23)μm (Vrad=23km/s),
ΔλHPFW=0.001μm
cf. previous study of [S IV]: R=2,000(ISO SWS: Bernard-Salas, et al 2001)• Rest wavelength of [S IV] in laboratory:
λlab=10.5105(1) μm
 VLSR ~ 38km/sec for [S VI], which iscomparable to the red-robe outflowfor CO2 (Nakashima et al. 2010 )Spectra of Venusian atmosphere at 10.1~10.8 μm
10.8222 μm

Parameters• Doppler shift : Δλ=(5.7±1.5)×10-4 μm(Systemic Velocity = 16±4.2 km/s)

Echellegram of Venusian atmosphere at 10.1~10.8 μm＊: 12CO2 ν3 ← ν1 , □: 12CO2 (ν3+ν2)←(ν1+ν2)○: 13CO2 ν3 ← ν1

• Rotational temperature(c) 12CO2 (ν3+ν2) ← (ν1+ν2) : 292±22 K(d) 13CO2 ν3 ← ν1 : 373±69 K
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Observation• Date: Apr. 5,13,17 2011
• Method: ON/OFF• Integration time: 1 min.
• Position: center + outer 14 points• Spatial resolution: 0.612arcsec

CO2 vibrational-rotational transitions
Spectra detected from Earth and Venus(a) 12CO2 ν3 ← ν1(b) 12CO2 ν3 ← 2ν2

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SPIE Astronomical Telescopes and Instrumentation 2012 Jul. 1