Description

This recipe is used to reduce an IFU arc spectrum. A wavelength calibration is obtained for each row of the spectrum. The file containing these calibrations is filed with the calibration system and used to apply a common, linear wavelength calibration to all rows of subsequent observations.

Read-noise and Poisson variances are added to the frame and a bad pixel mask is applied. The spectrum from each slice of the IFU is cut out of the frame and pasted in a new frame in such a way that there are no longer spaces between the spectra. The spectra are now arranged in the order in which they appear in the field of view and approximately aligned in the dispersion direction. The spectrum is divided by the flat-field.

The Figaro Iarc task is then used to obtain a wavelength calibration for each row, using a pre-calibrated arc file to provide the initial fit. Finally all the rows are scrunched to a common, linear wavelength scale to allow the observer to check that the wavelength calibration was correct (i.e. that the spectra are now straight).