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GNIRS Instrument Update

GNIRS Instrument Update. New Features Phase II problem spots Recent Science. Greg Doppmann Tucson NGO meeting 29 Nov. 2005. Instrument Upgrade - July 2005. Short Red and Blue Camera Lenses Replaced No more radiation events due to Thorium AR coating

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GNIRS Instrument Update

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  1. GNIRS Instrument Update New Features Phase II problem spots Recent Science Greg Doppmann Tucson NGO meeting 29 Nov. 2005

  2. Instrument Upgrade - July 2005 • Short Red and Blue Camera Lenses Replaced • No more radiation events due to Thorium AR coating • H2 and PAH narrowband filters added • Non saturating for bright acquisitions • Faint acquisitions for emission line objects • New XD filter installed • Increased throughput at J and X bands (~30% at 1 micron) • Cold Heads Replaced/Rebuilt

  3. GNIRS before… Before • Numerous radiation events impact the detector • Affected pixels flagged and interpolated

  4. GNIRS after… After • No radiation hits - only bad pixels remain

  5. GNIRS Cross-Dispersed Coverage 1.88 1.13 1.41 0.94 • XD 32 case shown • New XD filter installed • Better transmission at shorter wavelengths 0.81 0.70 K 0.63 H J  X I 1.90 1.27 0.95 2.54 1.52 1.09 0.85 

  6. GNIRS Phase II:Telluric Standards • Baseline calibration. One allowed per science target w/o charge to program. • Choose a “before” and “after” case for for longer observation (>20 minutes) science targets. • Exposure times scaled from integration time calculator on web (or see GNIRS page for K=5 case)

  7. GNIRS modes: what’s in demand? • XD 38% • IFU 22% • L or M band modes <5%

  8. GNIRS calibrations with GCAL • Wavelength Calibration - Arc Lamps (Ar & Xe) • Flatfielding - IR & QH lamps • Spatial trace along slit length - pinhole

  9. GNIRS calibrations with GCAL • Wavelength Calibration - Arc Lamps (Ar & Xe) • Flatfielding - IR & QH lamps • Spatial trace along slit length - pinhole

  10. GNIRS calibrations with GCAL • Wavelength Calibration - Arc Lamps (Ar & Xe) • Flatfielding - IR & QH lamps • Spatial trace along slit length - pinhole

  11. GNIRS Phase II Arcs, Flats & Pinhole • Use OT library - cut and paste • GNIRS web pages also detail configurations • New “observing class” in OT

  12. Spectrophotometric Standards • Use 3.0” wide slit. • Not a baseline calibration. • Use template flats and arcs for 1” slit. • See OT library

  13. GNIRS Phase II:Choosing Good Guide Stars • Use PWFS2 with DSS • Patrol Field: - min. radius 4.7’ - max. radius 6.9’

  14. GNIRS Phase II:Choosing Good Guide Stars • Choose V <= 15 mag • Need brighter stars in poor conditions - I.e. CC90 = 2 mag. extinction

  15. GNIRS Phase II:Blind Offsetting • Use for V >= 18 mag. objects • Define User1 offset star • Distance from Base < 1 arcmin.

  16. Acquisition Exposure Times • New H2 and PAH filters • Better exposure time guide

  17. GNIRS Phase II:Cross-Dispersed Acquisition Sequence • Image of the slit • Image of acq. Field • Extra lines for centering object in slit

  18. GNIRS Observing Conditions • SB • Always “any” • WV - “any” (J,H,K) or - 50%ile (M or blue L band) • CC - If photometric 50%ile (20%ile is same)

  19. NIR Atmospheric Transmission • L and M band affected by H20

  20. GNIRS IRAF Package Overview • Nsprepare - corrects for detector response • Nsreduce - flat fielding, sky subtraction, trims useful sections on array • Nswave - arc lines or sky lines for wavelength calibration • Nstelluric - removes atmospheric lines from science data • Nscalibrate - flux calibration using a photometric standard

  21. Recent Science with GNIRS • Van Dokkum et al., 2005 ApJ, 622L, 13 • Z=2.225 galaxy emission lines probe kinematics and metallicity • Silge et al., 2005 AJ, 130, 406 • dynamical measurements of Centaurus A characterize the central black hole mass. • Luhman et al., 2004 ApJ 617, 565 • Spectroscopic confirmation of the least massive brown dwarf known in Chamaeleon.

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