GeminiFocus July 2018 | Page 22

Figure 2. A small section of the IGRINS first-light spectrum. Purple - IGRINS spectrum of TW Hya from Gemini South. A small part of the K band in both cases. Green - combination of multiple epochs of spectra on the same object from McDonald observatory (from Sokal et al., 2018) Figure 3. IGRINS first-block (April) observing statistics. What’s unique about IGRINS is its revolu- tionary combination of spectral coverage (the entire H and K bands in a single expo- sure), high spectral resolution (R = 45,000) and high throughput (achieved through the use of a silicon immersion grating). It is also extremely compact and mechanically simple — having a single observing mode and no cryogenic moving parts. IGRINS adapts easily to different telescopes, re- quiring only a change of either fore-optics or input optics; in the case of Gemini, the input optics required replacement. IGRINS and Gemini South offer the most powerful combination yet. Since installation, IGRINS has been per- forming exactly as expected; at its spectral resolution (45,000), IGRINS’ sensitivity is about seven times better than any other high-resolution IR spectrometer on an 8- to 10-meter-class telescope, and it has many times the spectral coverage of other instruments at that resolution. Not sur- prisingly, demand for it at Gemini has been extremely high, with a list of 21 approved programs from the Gemini Participants, as well as a Large and Long Program of the instrument team. example of how much latitude matters. When IGRINS was run- ning at McDonald Observatory in the Northern Hemisphere, ob- servers worked hard for several years to obtain a spectrum of TW Hydrae, which was always very low in the Texas sky. With IGRINS at Gemini South, however, TW Hya was right overhead, and the first-light spectrum was not only quickly and easily observed, but it produced a spectrum that ri- vals the hard-earned published one from McDonald Observatory (Figure 2). With such remarkable first impressions, the IGRINS team is extremely excited to be sharing the IGRINS+Gemini combination with Gemini’s broad astronomical com- munity, and as its 2018 observing blocks at Gemini South draw to a close, we all look forward to the exciting results to come. IGRINS was scheduled for three separate observing blocks in Semester 2018A. As this issued goes to e-press IGRINS’ time at Gemini South is complete for now. In the first block, apart from worse than usual weather and one significant fault due to a compressor failure (Figure 3), we’ve spent almost the entire time observing IGRINS programs with one or two observations done in the regular queue. Hopefully the weather will hold up through the second and third blocks, but it’s already apparent This is IGRINS’ first visit to the Southern Hemisphere, and the results from our first light target, TW Hydrae, is a good 20 GeminiFocus July 2018