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Loading a spectral cube

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Open a directory navigator to select a local FITS file containing a SOFIA spectral cube downloaded from the SOFIA Science Archive.

After opening the file, the median of cube along the spectral dimension is shown on the image panel while the spectrum plotted on the left panel is obtained by summing all the spatial pixels for each wavelength.


In the case of FIFI-LS two further cubes are read and displayed:

  • the uncorrected flux
  • the exposure cube resulting in two further tabs in the image panel (median uncorrected flux and total exposure map) and curves on the spectral panel. In addition, also the atmospheric transmission used for the correction is shown in the spectral panel.


sospex is able to read GREAT fits cubes. In this case, only the flux panel is displayed since the exposure map is not saved in the GREAT products. The program checks if the flux is conserved in main beam temperature (T$_{mb}$) or antenna temperature (T$_{A*}$). Then it converts it into Jy/pixel using the conversion:

$S [Jy] = 971 \cdot T^{*}_{A} [K] $


$T^{*}_{A} [K] = \eta_{fss} \cdot \eta_{mb} \cdot T_{mb} [K]$

with $\eta_{fss} = 0.97$ and $\eta_{mb} = 0.67$.

To transform the flux from Jy/beam to Jy/pixel, a Gaussian PSF is assumed with the major axes specified in the header, using the fraction of flux in a pixel as:

$F_{pix} = 0.5 \cdot \rm{erf} (0.5\Delta_x/b_{maj}) \cdot \rm{erf} (0.5\Delta_y/b_{min})$,

where $\Delta_x$ and $\Delta_y$ are the pixel sides in arcsec, $b_{maj}$ and $b_{min}$ are the two axes of the beam, and $\rm{erf}$ is the error function.

A scale with the temperature in K is shown on the right of the spectrum.


It is possible to open Spectral Simple Cube generated by the Herschel pipeline and available in the Herschel Science Archive. After downloading the level 2 PACS spectroscopy products from the archive, search for the SpectralSimpleCube:

find . -name 'SpectralSimpleCube'

You will see the location of several files. For instance, in the case of the red array, simple spectral cubes are available for the following products:

  • ./level2/HPS3DDR/herschel.ia.dataset.spectrum.SpectralSimpleCube
  • ./level2/HPS3DEQDR/herschel.ia.dataset.spectrum.SpectralSimpleCube
  • ./level2/HPS3DPR/herschel.ia.dataset.spectrum.SpectralSimpleCube

Each of these directories contains a different product which is coded in the name of the directory.

Directory Meaning
HPS3DDR Herschel Pacs Spectroscopy 3D Drizzled Red
HPS3DEQDR Herschel Pacs Spectroscopy 3D Equidistant wavelength grid Drizzled Red
HPS3DPR Herschel Pacs Spectroscopy 3D Projected Red

The last one uses a normal projection. The other ones use drizzled projections. In particular the "Equidistant wavelength grid" is an interpolation along a wavelength grid with a constant step.

The PACS cubes have extensions for flux and exposure.


It is possible to resize the relative sizes of the image and spectral panel by clicking and dragging the splitter in between the two windows.

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