IMPALAS Fabry-Perot System

1
IMPALAS Fabry-Perot System

• Full two-dimensional spectroscopic imaging
• 8 (diameter) field of view
• seeing-limited spatial resolution
• Three spectral resolution modes
• 500 1000 2500 12500
• 25 km/s 5 km/s 1 km/s
• Wavelength range 430 860 nm (continuous)

2
Sensitivity
Resolution Absorption V20 500nm Absorption R20 600nm Emission 1 R Ha
500 12 s 19 s 3663 s
1000 24 s 38 s 2090 s
2500 74 s 118 s 1494 s
12500 370 s 589 s 966 s
Exposure times for a single S/N 10 per sample
image Samples Absorption 3x3 bp(0.78) Emission
4x4 bp (1.0) 9 15 exposures required for a
typical datacube
3
Etalons and Filters

• Dual etalon system
• R500-1000 low resolution etalon filter
• R2500 low mid-resolution etalons filter
• R12500 low high-resolution etalons filter

• Etalon finesse 30 (FWHM / Order Separation)
• peak transmission 80
• 30 filters required

4
Spectral Range

• Users desire 350 900 nm range
• Etalon coatings provide 1 octave range
• Science drivers
• kinematics
• emission Ha (656.3 nm) or OIII (500.7 nm)
• absorption Ha, Ca (854.2 nm), Mg (518.3 nm)
• nebular line analysis
• OIII (495.9500.7)/436.3, NII
  (654.8658.3)/575.5
• SII 671.6/673.1
• H Balmer ratios 656.3 486.1, 434.0

5

• Cosmology

Source Wavelength Strength Z range
Ha 656.3 1.00 0.00 0.31
OIII 500/7 0.56 0.00 0.72
OIII 405.9 0.18 0.00 0.73
Hß 486.1 0.24 0.00 0.77
OII 372.7 0.40 0.15 1.31
NeIV 242.3 0.12 0.78 2.55
CIII 190.8 0.17 1.25 3.51
CIV 154.9 0.47 1.78 4.55
La 121.6 1.00(?) 2.54 6.07
6

• Choose 430 860 nm spectral range
• satisfies largest number of users
• supports almost all imaging science programs
• Future upgrade
• either add blue etalon
• or strip recoat existing etalon (60 cost)
• in both cases add blue filters