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)

Sensitivity Resolution Absorption V=20 500nm R=20 600nm Emission 1 R Hα 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

Etalons and Filters Dual etalon system R=500-1000: low resolution etalon + filter R=2500: low + mid-resolution etalons + filter R=12500: low + high-resolution etalons + filter Etalon finesse 30 (FWHM / Order Separation) – peak transmission ~ 80% ~ 30 filters required

Spectral Range Users desire 350 – 900 nm range Etalon coatings provide ~ 1 octave range Science drivers kinematics emission: Hα (656.3 nm) or [OIII] (500.7 nm) absorption: Hα, Ca (854.2 nm), Mg (518.3 nm) nebular line analysis [OIII] (495.9+500.7)/436.3, [NII] (654.8+658.3)/575.5 [SII] 671.6/673.1 H Balmer ratios: 656.3 486.1, 434.0

Cosmology Source Wavelength Strength Z range Hα 656.3 1.00 0.00 – 0.31 [OIII] 500/7 0.56 0.00 – 0.72 405.9 0.18 0.00 – 0.73 Hβ 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 Lα 121.6 1.00(?) 2.54 – 6.07

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