Suppression of the near-infrared OH night-sky lines with fibre Bragg gratings - first results

S. C. Ellis, J. Bland-Hawthorn, J. Lawrence, A. J. Horton, C. Trinh, S. G. Leon-Saval, K. Shortridge, J. Bryant, S. Case, M. Colless, W. Couch, K. Freeman, L. Gers, K. Glazebrook, R. Haynes, S. Lee, H. G. Löhmannsröben, J. O'Byrne, S. Miziarski, M. Roth & 3 others B. Schmidt, C. G. Tinney, J. Zheng

Research output: Contribution to journalArticleResearchpeer-review

Abstract

The background noise between 1 and 1.8 μm in ground-based instruments is dominated by atmospheric emission from hydroxyl molecules. We have built and commissioned a new instrument, the Gemini Near-infrared OH Suppression Integral Field Unit (IFU) System (GNOSIS), which suppresses 103 OH doublets between 1.47 and 1.7μm by a factor of ≈1000 with a resolving power of ≈10000. We present the first results from the commissioning of GNOSIS using the IRIS2 spectrograph at the Anglo-Australian Telescope. We present measurements of sensitivity, background and throughput. The combined throughput of the GNOSIS fore-optics, grating unit and relay optics is ≈36per cent, but this could be improved to ≈46per cent with a more optimal design. We measure strong suppression of the OH lines, confirming that OH suppression with fibre Bragg gratings will be a powerful technology for low-resolution spectroscopy. The integrated OH suppressed background between 1.5 and 1.7 μm is reduced by a factor of 9 compared to a control spectrum using the same system without suppression. The potential of low-resolution OH-suppressed spectroscopy is illustrated with example observations of Seyfert galaxies and a low-mass star. The GNOSIS background is dominated by detector dark current below 1.67 μm and by thermal emission above 1.67 μm. After subtracting these, we detect an unidentified residual interline component of ≈860 ± 210 photons s -1 m -2arcsec -2μm -1, comparable to previous measurements. This component is equally bright in the suppressed and control spectra. We have investigated the possible source of the interline component, but were unable to discriminate between a possible instrumental artefact and intrinsic atmospheric emission. Resolving the source of this emission is crucial for the design of fully optimized OH suppression spectrographs. The next-generation OH suppression spectrograph will be focused on resolving the source of the interline component, taking advantage of better optimization for a fibre Bragg grating feed incorporating refinements of design based on our findings from GNOSIS. We quantify the necessary improvements for an optimal OH suppressing fibre spectrograph design.

LanguageEnglish
Pages1682-1695
Number of pages14
JournalMonthly Notices of the Royal Astronomical Society
Volume425
Issue number3
DOIs
Publication statusPublished - 21 Sep 2012

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night sky
Bragg gratings
near infrared
retarding
spectrographs
fibers
airglow
spectroscopy
optics
artifact
Seyfert galaxies
relay
background noise
thermal emission
dark current
fibre
artifacts
gratings
telescopes
stars

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Ellis, S. C. ; Bland-Hawthorn, J. ; Lawrence, J. ; Horton, A. J. ; Trinh, C. ; Leon-Saval, S. G. ; Shortridge, K. ; Bryant, J. ; Case, S. ; Colless, M. ; Couch, W. ; Freeman, K. ; Gers, L. ; Glazebrook, K. ; Haynes, R. ; Lee, S. ; Löhmannsröben, H. G. ; O'Byrne, J. ; Miziarski, S. ; Roth, M. ; Schmidt, B. ; Tinney, C. G. ; Zheng, J. / Suppression of the near-infrared OH night-sky lines with fibre Bragg gratings - first results. In: Monthly Notices of the Royal Astronomical Society. 2012 ; Vol. 425, No. 3. pp. 1682-1695.
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abstract = "The background noise between 1 and 1.8 μm in ground-based instruments is dominated by atmospheric emission from hydroxyl molecules. We have built and commissioned a new instrument, the Gemini Near-infrared OH Suppression Integral Field Unit (IFU) System (GNOSIS), which suppresses 103 OH doublets between 1.47 and 1.7μm by a factor of ≈1000 with a resolving power of ≈10000. We present the first results from the commissioning of GNOSIS using the IRIS2 spectrograph at the Anglo-Australian Telescope. We present measurements of sensitivity, background and throughput. The combined throughput of the GNOSIS fore-optics, grating unit and relay optics is ≈36per cent, but this could be improved to ≈46per cent with a more optimal design. We measure strong suppression of the OH lines, confirming that OH suppression with fibre Bragg gratings will be a powerful technology for low-resolution spectroscopy. The integrated OH suppressed background between 1.5 and 1.7 μm is reduced by a factor of 9 compared to a control spectrum using the same system without suppression. The potential of low-resolution OH-suppressed spectroscopy is illustrated with example observations of Seyfert galaxies and a low-mass star. The GNOSIS background is dominated by detector dark current below 1.67 μm and by thermal emission above 1.67 μm. After subtracting these, we detect an unidentified residual interline component of ≈860 ± 210 photons s -1 m -2arcsec -2μm -1, comparable to previous measurements. This component is equally bright in the suppressed and control spectra. We have investigated the possible source of the interline component, but were unable to discriminate between a possible instrumental artefact and intrinsic atmospheric emission. Resolving the source of this emission is crucial for the design of fully optimized OH suppression spectrographs. The next-generation OH suppression spectrograph will be focused on resolving the source of the interline component, taking advantage of better optimization for a fibre Bragg grating feed incorporating refinements of design based on our findings from GNOSIS. We quantify the necessary improvements for an optimal OH suppressing fibre spectrograph design.",
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author = "Ellis, {S. C.} and J. Bland-Hawthorn and J. Lawrence and Horton, {A. J.} and C. Trinh and Leon-Saval, {S. G.} and K. Shortridge and J. Bryant and S. Case and M. Colless and W. Couch and K. Freeman and L. Gers and K. Glazebrook and R. Haynes and S. Lee and L{\"o}hmannsr{\"o}ben, {H. G.} and J. O'Byrne and S. Miziarski and M. Roth and B. Schmidt and Tinney, {C. G.} and J. Zheng",
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Ellis, SC, Bland-Hawthorn, J, Lawrence, J, Horton, AJ, Trinh, C, Leon-Saval, SG, Shortridge, K, Bryant, J, Case, S, Colless, M, Couch, W, Freeman, K, Gers, L, Glazebrook, K, Haynes, R, Lee, S, Löhmannsröben, HG, O'Byrne, J, Miziarski, S, Roth, M, Schmidt, B, Tinney, CG & Zheng, J 2012, 'Suppression of the near-infrared OH night-sky lines with fibre Bragg gratings - first results' Monthly Notices of the Royal Astronomical Society, vol. 425, no. 3, pp. 1682-1695. https://doi.org/10.1111/j.1365-2966.2012.21602.x

Suppression of the near-infrared OH night-sky lines with fibre Bragg gratings - first results. / Ellis, S. C.; Bland-Hawthorn, J.; Lawrence, J.; Horton, A. J.; Trinh, C.; Leon-Saval, S. G.; Shortridge, K.; Bryant, J.; Case, S.; Colless, M.; Couch, W.; Freeman, K.; Gers, L.; Glazebrook, K.; Haynes, R.; Lee, S.; Löhmannsröben, H. G.; O'Byrne, J.; Miziarski, S.; Roth, M.; Schmidt, B.; Tinney, C. G.; Zheng, J.

In: Monthly Notices of the Royal Astronomical Society, Vol. 425, No. 3, 21.09.2012, p. 1682-1695.

Research output: Contribution to journalArticleResearchpeer-review

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T1 - Suppression of the near-infrared OH night-sky lines with fibre Bragg gratings - first results

AU - Ellis,S. C.

AU - Bland-Hawthorn,J.

AU - Lawrence,J.

AU - Horton,A. J.

AU - Trinh,C.

AU - Leon-Saval,S. G.

AU - Shortridge,K.

AU - Bryant,J.

AU - Case,S.

AU - Colless,M.

AU - Couch,W.

AU - Freeman,K.

AU - Gers,L.

AU - Glazebrook,K.

AU - Haynes,R.

AU - Lee,S.

AU - Löhmannsröben,H. G.

AU - O'Byrne,J.

AU - Miziarski,S.

AU - Roth,M.

AU - Schmidt,B.

AU - Tinney,C. G.

AU - Zheng,J.

PY - 2012/9/21

Y1 - 2012/9/21

N2 - The background noise between 1 and 1.8 μm in ground-based instruments is dominated by atmospheric emission from hydroxyl molecules. We have built and commissioned a new instrument, the Gemini Near-infrared OH Suppression Integral Field Unit (IFU) System (GNOSIS), which suppresses 103 OH doublets between 1.47 and 1.7μm by a factor of ≈1000 with a resolving power of ≈10000. We present the first results from the commissioning of GNOSIS using the IRIS2 spectrograph at the Anglo-Australian Telescope. We present measurements of sensitivity, background and throughput. The combined throughput of the GNOSIS fore-optics, grating unit and relay optics is ≈36per cent, but this could be improved to ≈46per cent with a more optimal design. We measure strong suppression of the OH lines, confirming that OH suppression with fibre Bragg gratings will be a powerful technology for low-resolution spectroscopy. The integrated OH suppressed background between 1.5 and 1.7 μm is reduced by a factor of 9 compared to a control spectrum using the same system without suppression. The potential of low-resolution OH-suppressed spectroscopy is illustrated with example observations of Seyfert galaxies and a low-mass star. The GNOSIS background is dominated by detector dark current below 1.67 μm and by thermal emission above 1.67 μm. After subtracting these, we detect an unidentified residual interline component of ≈860 ± 210 photons s -1 m -2arcsec -2μm -1, comparable to previous measurements. This component is equally bright in the suppressed and control spectra. We have investigated the possible source of the interline component, but were unable to discriminate between a possible instrumental artefact and intrinsic atmospheric emission. Resolving the source of this emission is crucial for the design of fully optimized OH suppression spectrographs. The next-generation OH suppression spectrograph will be focused on resolving the source of the interline component, taking advantage of better optimization for a fibre Bragg grating feed incorporating refinements of design based on our findings from GNOSIS. We quantify the necessary improvements for an optimal OH suppressing fibre spectrograph design.

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