GeminiFocus October 2018 | Page 16

versity of Toronto and the National Research Council-Herzberg (NRC-Herzberg) Institute of Astronomy and Astrophysics. This instru- ment will address a key limitation in existing adaptive optics (AO) facilities where integral field spectrographs are only able to observe single objects with adequate atmospheric correction, significantly limiting many scien- tific programs that could be efficiently ob- served with multiple integral field units. By taking advantage of the latest devel- opments in multi-object AO (MOAO) and integral field spectroscopy, GIRMOS is de- signed to have the ability to observe mul- tiple sources simultaneously at high angular resolution while obtaining spectra at the same time (Sivanandam et al., 2018). It ac- complishes this by exploiting the AO cor- rection from both a telescope-based AO system (either GeMS or the prospective Gemini North MCAO system — see page 12) and its own additional MOAO system that feeds four 1-2.4 µm integral field spectro- graphs (R ~ 3,000 and 8,000) that can each observe an object independently within a 2 arcminute field of view. While GeMS is a multi-conjugate AO (MCAO) system, which applies a global AO correc- tion over the entire field, the GIRMOS MOAO strives to optimally correct the observable field of each individual spectrograph. In gen- eral, MOAO applies a better correction to multiple specific spots over a field of view, while MCAO provides somewhat less correc- tion uniformly over the entire field of view. For the multiple-IFUs of GIRMOS, an MOAO system provides optimal performance with improved imaging performance along each integral field spectrograph’s line of sight. This powerful capability will be unique to GIRMOS as no other 8- to 10-meter-class observatory has a workhorse MOAO instrument. The current design parameters of the instru- ment concept are given in the table below. The instrument will also offer simultaneous imaging capability that is at a slightly lower resolution compared to the Gemini South Adaptive Optics Imager (GSAOI). The chosen design significantly increases the speed of integral field spectrograph surveys for sci- ence projects that target areas with high source densities, such as detailed observa- tions of distant galaxies. Telescope Feed Gemini 8.1-meter MCAO f/33 beam Individual IFS field of view (arcseconds) 1.06 × 1.06 2.1 × 2.1 4.2 × 4.2 8.4 × 8.4 (all IFS combined) MOAO Performance > 50% encircled energy within 0.1’’ IFS Spatial Pixel Size (milliarcseconds) (H and K bands) 25 × 25 50 × 50 100 × 100 100 × 100 (all IFS combined) Field of Regard 2’ diameter patrol field Spectral Resolution (R) 3,000 or 8,000 Wavelength Range 1.1−2.4 μm (J, H, or K bands) Spectrograph Throughput > 40% Number of IFSs 4 (with a goal of 8) Detector 4,096 × 4,096 HAWAI‘I-4RG for 4 spectral channels Imager Field of View 100 × 100’’ Imager Plate Scale (milliarcseconds) 25 Imager Wavelength 1.1−2.4 μm (J, H, or K bands) Range Imager Detector 14 GeminiFocus 4,096 × 4,096 HAWAI‘I-4RG October 2018