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Elodie archive Help

From the download field, the user can obtain two types of FITS files, the whole resampled spectrum and the s2D FITS files:
  1. The whole spectrum FITS file (spec button) is resampled in wavelength and is given in instrumental relative flux. For more details about this procedure please refer to the description of the full reduction procedure given in Prugniel & Soubiran 2001 paper.
    Each file has 3 extensions (HDU):
    The first (INTENSITY) gives the flux distribution calibrated in "instrumental" flux, that roughly corresponds to the flux measured on the detector (it is corrected for blaze and diffuse light effects). The region of some telluric absorption or of some gliches were masked and replaced by IEEE undefined values (be aware that some old FITS readers may not handle them intelligently and that you may have to replace them by regular values, (for example zeros).
    The second extension (FCA_NOR) is a flux calibration relation which can be used by Pleinpot to convert the spectrum into flux normalized to the pseudo-continuum. This normalization was used during the processing and may not be ideally suited for astrophysical use of the spectrum, like comparison with synthetic spectra to determine abundances. It is advised to determine a more relevant continuum using the spectrum in instrumental flux. It is of course possible to use the processing pipeline in the customize menu of the Elodie archive to get the standard continuum normalized spectrum.
    The third extension (NOISE) is the noise associated to each value in the first extension.

  2. The s2D FITS file (s2d button) consists in two extensions (HDU, Header Data Unit):
    The first extension contains the extracted and deblazed spectrum as a 2 dimensional image. Each line of 1024 pixels corresponds to an order, from the bluest to the reddest. There are 67 orders. On each line the wavelength grows from the first pixel to the last and the relation between pixels and wavelength is given by a series of keywords (Tchebicheff polynomials) described in the ELODIE manual. For more details read the Elodie documentation. The Pleinpot routine, img_wca_elodie, may be used to get the wavelength of each pixel.
    The s2d spectrum is corrected for the curvature of the échelle orders, but due to a bad correction of the scattered light residual curvature can still remain. Such a correction is made in the wavelength resampled spectrum.
    The second extension, a 2D image 1024x67, is the function used to correct the extracted spectrum from the blaze. Multiplying it with the first extension will restitute the extracted spectrum scaled in detected electrons. This form is useful in particular to determine the noise attached to each pixel.
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