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