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K.C. Roth, I. Jorgensen (Gemini Observatory), GDDS Team
The Gemini Multi-Object Spectrograph (GMOS) has been in use at the Gemini-North 8-m telescope on Mauna Kea since August 2001. A recent addition to the suite of GMOS capabilities is the implementation of Nod & Shuffle, proposed to Gemini Observatory by the GDDS (Gemini Deep Deep Survey) Team. Nod & Shuffle brings the principles of near-IR observing into the optical. By frequently nodding between object and sky positions, one can essentially eliminate the systematic sky-subtraction residuals that usually limit the sensitivity of MOS spectral observations, particularly in the red. Also, because the sky is derived from the same pixels on which the object light falls there is no need for the slit size to be any larger than the objects being observed. This allows one to place more slitlets and reach a higher spatial density of slits than is possible with conventional MOS spectroscopy.
We present a demonstration of the GMOS Nod & Shuffle capabilities based on long-slit data obtained as part of System Verification and MOS observations obtained under Director's Discretionary time in September 2002. We used Nod & Shuffle in single-band mode to place 74 science slits in the vicinity (central 2') of the QSO PKS1756+237. This QSO has a well-studied spectrum with several intervening absorption systems, including one (likely) damped absorber containing C I at z=1.6748. The purpose of these observations is to detect and characterize the galaxies responsible for or associated with the systems ``seen'' through absorption. We also present deep z' GMOS imaging and H+K' AO imaging taken with the University of Hawaii instrument Hokupa'a on Gemini of the central 20''. These data reveal a potential candidate for the DLA absorber lying 2.0'' from the QSO.
The Gemini Observatory is operated by AURA, Inc., under a cooperative agreement with the NSF on behalf of the Gemini partnership: NSF (United States), PPARC (United Kingdom), NRC (Canada), CONICYT (Chile), ARC (Australia), CNPq (Brazil) and CONICET (Argentina).
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The author(s) of this abstract have provided an email address for comments about the abstract: kroth@gemini.edu
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Bulletin of the American Astronomical Society, 34, #4
© 2002. The American Astronomical Soceity.