Gemini Observatory Press Releases

Gemini Near-Infrared Spectrograph (GNIRS) Nears First-Science

The Gemini Near-Infrared Spectrograph (GNIRS) is an infrared spectrograph for the Gemini South telescope that will operate from 1 to 5 microns.  GNIRS will offer two plate scales, a range of dispersions, as well as long-slit, cross-dispersed, and integral-field modes.  Designed and fabricated at NOAO in Tucson under the leadership of Jay Elias (Project Scientist), Dick Joyce (Co-Project Scientist), and Neil Gaughan (Project Manager) GNIRS’s versatility and high sensitivity will enable many exciting new science directions for Gemini in the area of near-infrared spectroscopy.

 As of early February, 2004 commissioning of GNIRS on Cerro Pachòn is well underway.  During 10 days in January, the majority of the tests for final acceptance of the instrument were completed, as well as some "first light" science observations (see figures).  Overall, the instrument behaved very well and all science channel mechanisms performed flawlessly.  The second commissioning run is now in progress and is focusing on "on-sky" performance of the different configurations, verification of the Integration Time Calculator (ITC), and a general exercising of the Gemini Observing software and operational procedures.  A beta release of the ITC is now available on the web.

 GNIRS has a near-infrared on-instrument wavefront sensor (OIWFS) for guiding and focus corrections.  Commissioning of the OIWFS has just begun and the on-sky performance has not yet been verified.  The Gemini peripheral wavefront sensors have been used with GNIRS for both commissioning runs and it is expected that this will be the guiding mode used for the first system verification run.

 The current GNIRS configuration does not include the Integral Field Unit (IFU) that was shipped from the University of Durham in January.  The IFU will be installed in late March (after the first system verification run) and is scheduled for first light in early April.

 The GNIRS facility infrared spectrograph is targeted for use during semester 2004B.  Because of the large number of observing modes, GNIRS commissioning is progressing in phases.  It is likely that GNIRS's fundamental modes (long-slit spectroscopy with resolutions R = 2000 and 6000; cross-dispersed spectroscopy at R=2000 with continuous coverage from 0.9 to 2.5 microns) will be available in 2004B.  There has been a strong response from the community for the system verification run for these modes, coming up in March.  For more information about GNIRS, please link to this recently updated web page.

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A spectum of the planetary nebula NGC 3918, demonstrating GNIRS cross-dispersed mode, with simultaneous coverage from 0.9 to 2.4um (=9000 to 24000 Angstroms) over 6 orders. NGC 3918 has an integrated K magnitude (the whole nebula) of K=8.8, and the spectrum is the sum of the light in the 6 arcsec long slit, integrating 12 minutes on-source (and 12 minutes on-sky). Data from overlapping orders are overlaid (seen around 1.5 um and below ~1.05um). The inset in the upper right shows more detail between 1.1um and 1.35um. As is typical of planetary nebulae, the spectrum is dominated by hydrogen and helium lines, but the high signal-to-noise ratio reveals lines from heavier elements such as forbidden FeII as well as molecular hydrogen emission at a comparatively low line intensity.
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Spectra of another planetary nebula, NGC 2867, demonstrate the "medium" resolution mode of GNIRS, R~6000. The 3 lower panels plot 3 individual spectra taken with different central wavelengths using the long slit (single order) mode in the K band. The upper panel shows the wavelength coverage of all 3 spectra together. The 1-D spectra are an average along the slit length of the ~12 arcsec extent of the nebula. NGC 2867 has an integrated K magnitude of 10.1; the total integration times were 24 minutes for the 1.99um spectrum and 12 minutes each for the 2.15 and 2.30um spectra (the object was dithered along the 99 arcsec slit such that all data were taken on-source). These spectra show a number of molecular hydrogen lines; the intensity in the 1-0 S(1) line at 2.12um is roughly 10x that seen in NGC3918.

Figure credits: Claudia Winge & Kevin Volk (Gemini Observatory), Alberto Ardila (Laboratorio Nacional de Astrofisica, Brazil), Dick Joyce (NOAO-Tucson, USA)