Difference: AAOmegaFileFormat (10 vs. 11)

Revision 112008-07-26 - RonHeald

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AAOmega File Format (or, which spectrum is which object?)

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Extension	IRAF format	Contents

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Primary	.fits[0]	WxN image containing the spectrum (W pixels long) for each fibre of the N spectra
Variance	.fits[1]	WxN image containing the variance array for the data
Fibre Table	.fits[2]	FITS binary table, with N rows, one for each fibre. Each row contains information for each object such as RA, Dec, 2dF

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Primary	.fits[0]	The primary extension in the FITS file is a WxN image where W is the number of pixels in each spectrum, and N is the number of spectra represented. This is 400 for AAOmega data, 392 science fibres and 8 guide fibres. Unused science fibres and Sky spectra, are included in the output file along with the guide fibres spectra, even though the spectra contain no information, as this simplifies book keeping, and is a small disc space overhead. In the case where multiple sets of AAOmega datasets, which contained a subset of common objects, have been combined, the format is a little more complex, and is explained separately below.
Variance	.fits[1]	The variance extension is also a WxN array. Each member contains the variance for the corresponding element in the primary extension.
Fibre Table	.fits[2]	FITS binary table, with N rows, one for each fibre. Each row contains information for the fibre such as object name, position, etc. Full details are given below.

Other Extensions

The files contain several other extensions which are generally only useful with in depth analysis of the data. They are not necessarily in order and are accessed by name. They are described here.

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The primary extension in the FITS file is a WxN image where W is the number of pixels in each spectrum, and N is the number of spectra represented. This is 400 for AAOmega data, 392 science fibres and 8 guide fibres. Unused science fibres and Sky spectra, are included in the output file along with the guide fibres spectra, even though the spectra contain no information, as this is seen to simplify book keeping, and is a small disc space overhead. In the case where multiple sets of AAOmega datasets, which contained a subset of common objects, have been combined, the format is a little more complex, and is explained separately below.

The variance extension is also a WxN array. Each member contains the variance for the corresponding element in the primary extension.

The fibre table is described below.

The extensions can be accessed in a number of ways given below.

The files output by 2dfdr also include data at intermediate processing steps. They are not normally used by scientist. They are described here.

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