1dspec extracts 1-dimensional spectra from a set of 2-dimensional spectra stored in a 2spec file, using one of two methods. If the optimal parameter is set to “true”, an optimal extraction is performed, using the method described in Horne (1986), optionally with cosmic ray rejection. If the optimal parameter is not “true”, the spectrum in a specified range of slit position is simply summed. The resulting spectra are stored as a set of 3-d image extensions, one per spectrum. Each spectrum consists of two planes, each one pixel wide. The first plane contains the spectrum and the second the 1-sigma errors. The output flux units are counts per angstrom.
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USAGE |
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INPUT |
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OUTPUT |
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PARAMETERS |
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Optimal extraction uses the method described in Horne (1986). If requested, cosmic rays are automatically removed. One may use the entire length of the slit, but- if the total size of the objects is much smaller than the slit length, or if one is not interested in preserving the spectrophotometric information in the spectrum- noise can be somewhat reduced by setting a smaller extraction region using the parameter hwidth. If the spectra are bad near the slit ends, it is recommended to either use a smaller value of hwidth, or set the edge parameter to exclude the bad ends. If this entry is left blank, or set to a size larger than the half-length of the longest slit, the entire slit length is used.
Non-optimal extraction simply sums the spectrum over the interval of slit position specified by hwidth. If requested, the centroid of the spectrum along the slit is first found, and the extraction range centered on that position. Otherwise the spectrum center specified in the input file is used.