For each partially or fully extended source observed in HR sparse mode there are two sets of FF results; one for the point-source calibrated spectra and one for the extended-source calibrated spectra
The "Flag" column indicates semi-extended targets and extended targets with
EXT. Whether a highly processed data product was used is indicated with the
HPDP flag. You can visit the Spectrometer calibrators legacy data page or click on a HPDP flag in the table to find the HPDP used. A
BGS flag indicates background corrected data was used, where the mean of the spectra from several smoothed off-axis detectors was subtracted (following Hopwood et al. 2015). You can visit the Background subtracted data page or click on a BGS flag in the table to find the BGS data used.
Source that are assigned the
EXT flags, may see issues with their Feature Finder results, as the point-source calibration scheme is optimal for point-like sources and extended-source calibration optimal for fully extended sources. The postcard pairs for these observations provide a quick way to compare the calibration schemes applied for sparse-mode (single-pointed) FTS products associated to sources with some spatial extent. If a source had an intrinsic size much larger than the beam (> 42"), the FF results for point-source calibrated data may show issues, such as fringing found as features or a poor fit to the continuum. For partially extended sources, there may be weaker features in the SSW spectrum, while high fringing may still be present in the SLW spectrum.
For sources with spatial extent, the extended-source calibrated products are provided as an alternative, as these may offer improved results for one or both of the centre detectors (SLWC3 and SSWD4). The extended-source calibrated FF results may also be better for some sources that are not fully extended, but do have significant extent within the FTS beam. Therefore all sources that have been classed as semi-extended (by assessing any discontinuity between the bands and, where available, associated PACS photometer maps) are included. However, if a source is not significantly extended, the extended-source calibrated FF results may not improve upon the point-source calibrated ones. The point- and extended-source calibrated FF results have been visually compared for all the sources assigned a semi/fully extended classification. If the extended-source calibrated results were found to improve upon the respective point-source results, that is indicated in the "flag" column with an asterisk (e.g.
EXT*) and for which detectors (SLWC3/SSWD4). Improvements include extra features found, fewer spurious features or an improved fit to the continuum. It may be that neither calibration scheme produces a satisfactory FF results, or the results are the same.