SPIRE Spectrometer: re-gridded hyper-spectral cubes


The best spectral resolution expected for high-resolution SPIRE Spectrometer data is 1.184 GHz, which is representative for nearly all the spatial-pixels of any spectral cube where one or more of the constituent spectra have degraded resolution. This is due to the large number of spectra projected into any given cube and because the degraded spectra are always towards the outer ring of either of the Spectrometer bolometer detector arrays.

However, there are 22 SPIRE Spectrometer mapping observations that suffer from one or more individual spectra that have higher than expected spectral resolution. In the Herschel Science Archive, the final standard product generation (SPG) produced hyper-spectral cubes (cubes) reports the highest resolution of all the spectra included when projecting the cube. This value is stored in the top-level metadata, with the FITS keyword ACTRES.  These 22 mapping observations in question were re-gridded without change to the majority of their spatial pixels, although one or more pixels (of low quality) can be lost at the edge of the map. The new cubes, therefore, all report an actual unpadded spectral resolution of 1.18448225 GHz in their metadata.

The spectra used to create the new cubes were reduced with HIPE version 14.1, using spire_cal_14_3.

HPDP products

The cubes are extended-source calibrated in standard Spectrometer surface brightness units of W/m2/Hz/sr and presented in the same format as their HSA counterpart. There are four cubes per observation affected: Naive projected, convolution projected (CP), and apodized versions of these. All 22 observations were taken in high-resolution (HR) mode. These data have been made available to avoid confusion over their science readiness, and spectral resolution, and the need to re-project the cubes before they can be analysed.

The products are available in the Herschel Legacy HPDP repository area.