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Adaptive filtering of Echelle spectra of distant QuasarsThe study of the Ly alpha - forest of distant (approximately greater than 3) Quasars is an important tool in obtaining a more detailed picture of the distribution of matter along the line of sight and thus of the general distribution of matter in the Universe and is therefore of important cosmological significance. Obviously, this is one of the tasks where spectral resolution plays an important role. The spectra used were obtained with the EFOSC at the ESO 3.6m telescope. Applying for the data reduction the standard Echelle procedure, as it is implemented for instance in the MIDAS-package, one uses stationary filters (e.g. median) for noise and cosmic particle event reduction in the 2-dimensional Echelle image. These filters are useful if the spatial spectrum of the noise reaches essentially higher frequencies then the highest resolution features in the image. Otherwise the resolution in the data will be degraded and the spectral lines smoothed. However, in the Echelle spectra the highest resolution is already in the range of one or a few pixels and therefore stationary filtering means always a loss of resolution. An Echelle reduction procedure on the basis of a space variable filter described which recognizes the local resolution in the presence of noise and adapts to it is developed. It was shown that this technique leads to an improvement in resolution by a factor of 2 with respect to standard procedures.
Document ID
19940018047
Acquisition Source
Legacy CDMS
Document Type
Conference Paper
Authors
Priebe, A. (Astrophysical Inst. Potsdam, Germany)
Liebscher, D.-E. (Astrophysical Inst. Potsdam, Germany)
Lorenz, H. (Astrophysical Inst. Potsdam, Germany)
Richter, G.-M. (Astrophysical Inst. Potsdam, Germany)
Date Acquired
September 6, 2013
Publication Date
January 1, 1992
Publication Information
Publication: NASA, Washington, Second Annual Conference on Astronomical Data Analysis Software and Systems. Abstracts
Subject Category
Astronomy
Accession Number
94N22520
Distribution Limits
Public
Copyright
Work of the US Gov. Public Use Permitted.

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