GNIRS Instrument Update New Features Phase II problem
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 • H 2 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
GNIRS before… • Numerous radiation events impact the detector • Affected pixels flagged and interpolated Before
GNIRS after… • No radiation hits only bad pixels remain After
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 2. 54 1. 90 1. 27 0. 95 1. 52 1. 09 0. 85
GNIRS Phase II: Telluric Standards • Baseline calibration. One allowed per science target w/o charge to program. • Choose a “before” and “after” case for longer observation (>20 minutes) science targets. • Exposure times scaled from integration time calculator on web (or see GNIRS page for K=5 case)
GNIRS modes: what’s in demand? • XD 38% • IFU 22% • L or M band modes <5%
GNIRS calibrations with GCAL • Wavelength Calibration - Arc Lamps (Ar & Xe) • Flatfielding - IR & QH lamps • Spatial trace along slit length - pinhole
GNIRS calibrations with GCAL • Wavelength Calibration - Arc Lamps (Ar & Xe) • Flatfielding - IR & QH lamps • Spatial trace along slit length - pinhole
GNIRS calibrations with GCAL • Wavelength Calibration - Arc Lamps (Ar & Xe) • Flatfielding - IR & QH lamps • Spatial trace along slit length - pinhole
GNIRS Phase II Arcs, Flats & Pinhole • Use OT library - cut and paste • GNIRS web pages also detail configurations • New “observing class” in OT
Spectrophotometric Standards • Use 3. 0” wide slit. • Not a baseline calibration. • Use template flats and arcs for 1” slit. • See OT library
GNIRS Phase II: Choosing Good Guide Stars • Use PWFS 2 with DSS • Patrol Field: - min. radius 4. 7’ - max. radius 6. 9’
GNIRS Phase II: Choosing Good Guide Stars • Choose V <= 15 mag • Need brighter stars in poor conditions - I. e. CC 90 = 2 mag. extinction
GNIRS Phase II: Blind Offsetting • Use for V >= 18 mag. objects • Define User 1 offset star • Distance from Base < 1 arcmin.
Acquisition Exposure Times • New H 2 and PAH filters • Better exposure time guide
GNIRS Phase II: Cross-Dispersed Acquisition Sequence • Image of the slit • Image of acq. Field • Extra lines for centering object in slit
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)
NIR Atmospheric Transmission • L and M band affected by H 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
Recent Science with GNIRS • Van Dokkum et al. , 2005 Ap. J, 622 L, 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 Ap. J 617, 565 – Spectroscopic confirmation of the least massive brown dwarf known in Chamaeleon.
- Slides: 21