Post on 20-Dec-2015
Grism Spectroscopy with FLITECAM
Erin C. Smith (UCLA)Ian S. McLean (UCLA)
FLITECAM1- 5.5 micron NIR camera
1024x1024 InSb Aladdin III detector
Optics cooled to ~ 80K with LN2
Detector controlled at 30K
SOFIA
8 arcminute circular FOV
.43 arcsec/pixel (SOFIA)
.48 arcsec/pixel (Lick)
Entrance aperture Slit mechanism Collimator
Dual Filter Wheel Re-imaging optics
Detector
Why spectroscopy?
• Water Vapor monitor calibration– Resolve 2.5 micron water line (need R~1000)
• Allows low background, low water vapor spectroscopy in the thermal (3-5.5 micron IR)– No spectral coverage by Spitzer at these wavelengths
Science
PAH features at 3.3 m
Water ices 2.5-4.6 m
Pa-a (1.87 m )
Br- (4.05 m )
Grism Spectroscopy
d
dpupil
Xmm=dpupil/cos AA
i
d
grism normal
T m c= (n –1) sin A
R = 206265 (n – 1) dpupil tan A / Dtel sarc ,
(max/min wavelength) = c +/- [(n – 1) dpix cos A / Fcam m T] *Npix/2,
KRS-5
• N~2.4• Thalium bromo-iodide
• Manufactured by Zeiss-Jena– Can make grisms with T=651/n, up to 40 degrees
Grism T Order OSF c
A 162.75 1 L&M 4.96
A 162.75 2 Klong 2.5 A 162.75 3 Hwide 1.69 B 217 1 L&M 3.73 B 217 2 Hwide 1.86 B 217 3 J 1.28 C 130.2 2 L&M 3.11 C 130.2 3 Kwide 2.11 C 130.2 4 H 1.62
Wavelength coverage
Slit
Lab testing• Neon Argon lamps used to calibrate wavelength solutions
• Slit width found to be slightly larger than designed, narrow slit is 1.3”, wide slit is 2.35” wide
• R ~1700/900
FLITECAM also mounts to the Shane 3 meter telescope at Lick Observatory
Imaging mode commissioned October 2002
Spectroscopy mode was commissioned in June 2004
Difference RAW
C + KwideC + LM
69 Leo
A0V star, for telluric standards
High backgrounds at Lick require differences in thermal IR
1.872
2.346
2.756
3.467
Gl406- (M5.5)
Raw H band spectrum
A-B spectrumHigh-res
position B
High res position A
Data reduction
NGC 7027
Imaging & spectroscopy
• Switching between spectroscopy and imaging takes less than 20 seconds
• Using narrow band filters, we can make maps of spectral features, then use spectroscopy to investigate
Aboard SOFIA