Near-infrared sky background fluctuations at mid- and low latitudes

The emission of the upper atmosphere introduces an additional variable component into observations of astronomical objects in the NIR 700–3,000 nm range. The subtraction of this component is not easy because it varies during the night by as much as 100% and it is not homogeneous over the sky. A program aimed at measuring and understanding the main characteristics of the atmospheric NIR emission was undertaken. A 512 × 512 CCD camera equipped with a RG780/2 mm filter is used to obtain images of the sky in a 36° × 36° field of view. The intensities of a given star and of the nearby region devoid of star in a 439 arcmin2 area are monitored during periods of time of several hours. The sky intensity measured in the 754–900 nm bandpass, reduced to zenith and zero airmass is comprised between mag20 and mag18.5 per arcsecond2. A diminution by a factor of two during the night is frequently observed. Intensity fluctuations having an amplitude of 15% and periods of 5–40 min are present in the images with a structure of regularly spaced stripes. The fluctuations of the NIR sky background intensity are due to (1) the chemical evolution of the upper atmosphere composition during the night and (2) dynamical processes such as tides with periods of 3–6 h or gravity waves with periods of several tens of minutes. We suggest that a monitoring of the sky background intensity could be set up when quantitative observations of astronomical objects require exposure times longer than ~10 min. The publication is illustrated with several video films accessible on the web site http://www.obs-besancon.fr/nirsky/. Enter username: nirsky and password: skynir.

[1]  A. W. Peterson,et al.  Infrared Photography of OH Airglow Structures , 1973, Nature.

[2]  Paul Berry,et al.  The VISTA IR camera , 2004, SPIE Astronomical Telescopes + Instrumentation.

[3]  J. Polanyi,et al.  Infrared chemiluminescence from H + O3 at low pressure , 1968 .

[4]  C. Coulman,et al.  Optical seeing-mechanism of formation of thin turbulent laminae in the atmosphere. , 1995, Applied optics.

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

[6]  K. Ashman,et al.  Globular cluster systems formed in galaxy mergers , 1993 .

[7]  Julien Borgnino,et al.  Theoretical spatiotemporal analysis of angle of arrival induced by atmospheric turbulence as observed with the grating scale monitor experiment , 1997 .

[8]  Gavin Dalton,et al.  The Visible & Infrared Survey Telescope for Astronomy , 2004 .

[9]  Jean-Gabriel Cuby,et al.  Night-sky spectral atlas of OH emission lines in the near-infrared , 2000 .

[10]  Anomalous surface brightness fluctuations in NGC 4489 , 2000, astro-ph/0011276.

[11]  H. Urey.  The Atmospheres of the Planets , 1959 .

[12]  Guy Moreels,et al.  Ground-based satellite-type images of the upper-atmosphere emissive layer. , 2002, Applied optics.

[13]  Guy Moreels,et al.  Bi-dimensional observation of waves near the mesopause at auroral latitudes , 1985 .

[14]  B. Vicente,et al.  TCS-CAIN: a deep multi-colour NIR survey of the Galactic plane , 2006 .

[15]  M. Taylor,et al.  Long-period wave signatures in mesospheric OH Meinel (6,2) band intensity and rotational temperature at mid-latitudes , 2001 .

[16]  Robert G. Fleagle,et al.  An Introduction to Atmospheric Physics , 1980 .

[17]  Yuk L. Yung,et al.  Vertical transport and photochemistry in the terrestrial mesosphere and lower thermosphere (50–120 km) , 1981 .

[18]  David W. Tarasick,et al.  THE OBSERVABLE EFFECTS OF GRAVITY WAVES ON AIRGLOW EMISSIONS , 1990 .

[19]  Liverpool John Moores University,et al.  Colour–colour diagrams and extragalactic globular cluster ages - Systematic uncertainties using the (V – K) – (V – I) diagram , 2006, astro-ph/0610252.

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

[21]  Jean P. Brodie,et al.  Extragalactic Globular Clusters and Galaxy Formation , 2006 .

[22]  David G. Andrews,et al.  An Introduction to Atmospheric Physics , 2000 .

[23]  J. Cuby,et al.  ISAAC: 18 Months of Paranal Science Operations , 2000 .

[24]  James Liebert,et al.  The Two Micron All Sky Survey (2MASS): Overview and Status , 1997 .

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

[26]  M. Herse,et al.  Photographic evidence of waves around the 85 km level , 1977 .

[27]  G. Moreels,et al.  Fourier analysis of a virtual satellite view of the NIR atmospheric emission over Europe , 2003 .