The case for OH suppression at near-infrared wavelengths

We calculate the advances in near-infrared (NIR) astronomy made possible through the use of fibre Bragg gratings to selectively remove hydroxyl emission lines from the night sky spectrum. Fibre Bragg gratings should remove OH lines at high resolution (R = 10 000), with high suppression (30 dB) whilst maintaining high throughput (≈90 per cent) between the lines. Devices presently under construction should remove 150 lines in each of the J and H bands, effectively making the night sky surface brightness ≈4 mag fainter. This background reduction is greater than the improvement adapative optics makes over natural seeing; photonic OH suppression is at least as important as adaptive optics for the future of cosmology. We present a model of the NIR sky spectrum, and show that the interline continuum is very faint (≈80 photons s −1 m −2 arcsec −2 μm −1 on the ecliptic plane). We show that OH suppression by high dispersion, that is, ‘resolving out’ the skylines, cannot obtain the required level of sensitivity to reach the interline continuum due to scattering of light. The OH lines must be suppressed prior to dispersion. We have simulated observations employing fibre Bragg gratings of first light objects, highredshift galaxies and cool, low-mass stars. The simulations are of complete end-to-end systems from object to detector. The results demonstrate that fibre Bragg grating OH suppression will significantly advance our knowledge in many areas of astrophysics, and in particular will enable rest-frame ultraviolet observations of the Universe at the time of first light and reionization.

[1]  K. Glazebrook,et al.  Microslit Nod‐Shuffle Spectroscopy: A Technique for Achieving Very High Densities of Spectra , 2000, astro-ph/0011104.

[2]  Anthony E. Ennos,et al.  Stresses developed in optical film coatings. , 1966, Applied optics.

[3]  W. V. Breugel,et al.  Imaging the Universe in Three Dimensions , 2000 .

[4]  S. Oh,et al.  Probing the dark ages with metal absorption lines , 2002, astro-ph/0201517.

[5]  J. Bland-Hawthorn,et al.  Rugate filters for OH-suppressed imaging at near-infrared wavelengths , 1997, astro-ph/9707298.

[6]  A. Cox,et al.  Allen's astrophysical quantities , 2000 .

[7]  Z. Haiman,et al.  Quasar Strömgren Spheres Before Cosmological Reionization , 2000, astro-ph/0006376.

[8]  Jordi Miralda-Escude,et al.  Reionization of the Intergalactic Medium and the Damping Wing of the Gunn-Peterson Trough , 1997, astro-ph/9708253.

[9]  G. Herzberg.  Molecular Spectra and Molecule Structure. I. Diatomic Molecules. , 1940 .

[10]  Ian R. Parry,et al.  Fiber multi-object spectrograph (FMOS) for the Subaru Telescope , 2000, Astronomical Telescopes and Instrumentation.

[11]  Patrick J. McCarthy,et al.  Hubble Space Telescope Imaging and Keck Spectroscopy of z ≈ 6 i-Band Dropout Galaxies in the Advanced Camera for Surveys GOODS Fields , 2004 .

[12]  Joss Bland-Hawthorn,et al.  Coupling light into few-mode optical fibres I: The diffraction limit. , 2007, Optics express.

[13]  J. Bland-Hawthorn,et al.  Optimization algorithm for ultrabroadband multichannel aperiodic fiber Bragg grating filters. , 2008, Journal of the Optical Society of America. A, Optics, image science, and vision.

[14]  Demetri Psaltis,et al.  Multi-notch holographic filters for atmospheric lines suppression , 2004, SPIE Astronomical Telescopes + Instrumentation.

[15]  Brent Ellerbroek,et al.  Advances in Adaptive Optics II , 2006 .

[16]  S. Faber,et al.  Velocity dispersions and mass-to-light ratios for elliptical galaxies. , 1976 .

[17]  et al,et al.  The SUBARU Deep Field Project: Lymanα Emitters at a Redshift of 6.6 , 2005 .

[18]  H. Murakami,et al.  Rocket observation of the near-infrared spectrum of the sky , 1992 .

[19]  S. Ramsay,et al.  Non-thermal emission in the atmosphere above Mauna Kea , 1992 .

[20]  Subaru Telescope,et al.  CISCO: Cooled Infrared Spectrograph and Camera for OHS on the Subaru Telescope , 2002 .

[21]  Andreas Kelz,et al.  Development of the wide-field IFU PPak , 2004, SPIE Astronomical Telescopes + Instrumentation.

[22]  Richard McMahon,et al.  DAzLE: the dark ages z (redshift) Lyman-α Explorer , 2004, SPIE Astronomical Telescopes + Instrumentation.

[23]  Bruce A. Peterson,et al.  On the Density of Neutral Hydrogen in Intergalactic Space , 1965 .

[24]  G. Bruzual,et al.  Stellar population synthesis at the resolution of 2003 , 2003, astro-ph/0309134.

[25]  Haojing Yan,et al.  Candidates of z ≃ 5.5-7 Galaxies in the Hubble Space Telescope Ultra Deep Field , 2004 .

[26]  I. Meinel,et al.  OH Emission Bands in the Spectrum of the Night Sky. , 1950 .

[27]  R. P. Lowe,et al.  Vibrational population distribution in the hydroxyl night airglow , 1983 .

[28]  Gary R. Swenson,et al.  Atmospheric gravity wave signatures in the infrared hydroxyl OH airglow , 2000 .

[29]  R. Davies,et al.  A method to remove residual OH emission from near-infrared spectra , 2007 .

[30]  T. Shimazaki,et al.  A model calculation of the diurnal variation in minor neutral constituents in the mesosphere and lower thermosphere including transport effects , 1970 .

[31]  Donald N. B. Hall,et al.  OH airglow suppressor spectrograph: design and prospects , 1993, Defense, Security, and Sensing.

[32]  D. Osterbrock,et al.  NIGHT-SKY HIGH-RESOLUTION SPECTRAL ATLAS OF OH AND O2 EMISSION LINES FOR ECHELLE SPECTROGRAPH WAVELENGTH CALIBRATION , 1996 .

[33]  M. Rees,et al.  The Earliest Luminous Sources and the Damping Wing of the Gunn-Peterson Trough , 2000, astro-ph/0006271.

[34]  H. Rix,et al.  The James Webb Space Telescope , 2006, astro-ph/0606175.

[35]  Alexander S. Szalay,et al.  Evidence for Reionization at z ∼ 6: Detection of a Gunn-Peterson Trough in a z = 6.28 Quasar , 2001, astro-ph/0108097.

[36]  S. M. Fall,et al.  Observable Properties of Cosmological Reionization Sources , 2003, astro-ph/0309835.

[37]  R. Rebolo,et al.  A Methane, Isolated, Planetary-Mass Object in Orion , 2002, astro-ph/0206353.

[38]  Constraints on the Cosmic Near Infrared Background Excess from NICMOS Deep Field Observations , 2006, astro-ph/0612033.

[39]  E. L. Wright,et al.  The COBE Diffuse Infrared Background Experiment Search for the Cosmic Infrared Background. II. Model of the Interplanetary Dust Cloud , 1997, astro-ph/9806250.

[40]  A. Pickles,et al.  OBSERVATIONS OF THE OH AIRGLOW EMISSION , 1993 .

[41]  R. Hata,et al.  OHS: OH-Airglow Suppressor for the Subaru Telescope , 2001 .

[42]  J. Lennard-jones,et al.  Molecular Spectra and Molecular Structure , 1929, Nature.

[43]  H. Murakami,et al.  IRTS Observation of the Near-Infrared Spectrum of the Zodiacal Light , 1996 .

[44]  Adam J. Burgasser,et al.  The NIRSPEC Brown Dwarf Spectroscopic Survey. I. Low-Resolution Near-Infrared Spectra , 2003, astro-ph/0309257.

[45]  G. Herzberg,et al.  Molecular Spectra and Molecular Structure , 1992 .

[46]  Board on Physics.  Astronomy and Astrophysics in the New Millennium , 2001 .

[47]  James A. Arns,et al.  Volume‐Phase Holographic Gratings and the Efficiency of Three Simple Volume‐Phase Holographic Gratings , 2000 .

[48]  Kevin Krisciunas,et al.  A MODEL OF THE BRIGHTNESS OF MOONLIGHT , 1991 .

[49]  T. Woods,et al.  Scattered-light properties of diffraction gratings. , 1994, Applied optics.

[50]  S. D. Ryder,et al.  Science Programs for a 2-m Class Telescope at Dome C, Antarctica: PILOT, the Pathfinder for an International Large Optical Telescope , 2005, Publications of the Astronomical Society of Australia.

[51]  R. Oppermann.  Molecular spectra and molecular structure. I. Diatomic molecules , 1940 .

[52]  Andreas Kelz,et al.  Ground-based instrumentation for astronomy , 2004 .

[53]  NASA Ames Research Center,et al.  The Mauna Kea Observatories Near-Infrared Filter Set. III. Isophotal Wavelengths and Absolute Calibration , 2005 .

[54]  M. Langlois,et al.  Society of Photo-Optical Instrumentation Engineers , 2005 .

[55]  J. Bland-Hawthorn,et al.  New approach to atmospheric OH suppression using an aperiodic fibre Bragg grating. , 2004, Optics express.

[56]  Eli Atad-Ettedgui,et al.  Optical fabrication, metrology, and material advancements for telescopes : 24-25 June 2004, Glasgow, Scotland, United Kingdom , 2004 .