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

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
• 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
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 CrossDispersed 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
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 PWFS2 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. CC90 = 2 mag.
extinction
GNIRS Phase II:
Blind Offsetting
• Use for V >= 18
mag. objects
• Define User1 offset
star
• Distance from Base
< 1 arcmin.
Acquisition Exposure Times
• New H2 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
H20
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 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.