Difference: HipeWhatsNew14x (77 vs. 78)

Revision 782017-02-01 - KatrinaExter

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What's new in version 14.x

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Spectroscopy

Changed:
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  • Extended source correction. The extended-source calibrated rebinned cubes (level2) are subjected to a correction that accounts for the non-uniform illumination of the PACS IFU field-of-view. It stems from the fact that the 9.4"x9.4" spaxel edges are less responsive than their centres, translating into a spaxel active area of approximately 8"x8" where the response is flat. This effect is more severe at shorter wavelengths, and affects (very) extended emission, as well as off-centred point sources and any source that has a size between a point and a very extended. All Level 2/2.5 cubes for these types of sources will be affected, whether pointed or mapping.
    Hence, for centred point source extracted with the task extractCentralSpectrum, no change to the spectra are expected in this version of HIPE because of this effect. For very extended sources, we have developed a new Extended Source Correction calibration file (ExtendedSourceLoss, applied in the pipeline tasks specRespCal and specRespCalToTelescope), and this incorporates the necessary correction as part of the spatial flatfielding for the PACS spectrometer. For these sources, the fluxes of the spectra will differ to what was obtained in previous versions of HIPE. For intermediate sources, a more complex analysis is necessary to estimate the flux loss, and a task to do this will be provided in HIPE 15.
    The fluxes of the spaxels of all cubes will be increased by ~30% in the blue to ~5% in the red. The calibration file can be inspected to extract the curve:
    w = calTree.spectrometer.extendedSourceLoss["wavelength"].data
    f = calTree.spectrometer.extendedSourceLoss["fraction"].data
    p=PlotXY(w, 1./f)
    After such a correction, a source of flat surface brightness within the field of view of a single pointing will be well calibrated at the level of the rebinned cubes (i.e. level2). The flux loss between the detectors was already accounted for in the point-source calibration correction in the correspondent calibration file, therefore, point-source calibrated spectra of centred point sources are not affected. For this reason, in HIPE 14, the extractCentralSpectrum task checks and removes the extendedSourceLoss correction from the level2 cubes, in case it has been applied, before extracting the final point source corrected spectrum. However, if working with off-centred point sources and using the tasks extractSpaxelSpectrum and pointSourceLossCorrection, this correction is not taken out, and hence the results will be incorrect. An extra task/function is necessary: this task can be found in the "Point source loss correction (any spaxel)" script in the Scripts->PACS useful menu.
>
>
  • Extended source correction. The extended-source calibrated rebinned cubes (level2) are subjected to a correction that accounts for the non-uniform illumination of the PACS IFU field-of-view. It stems from the fact that the 9.4"x9.4" spaxel edges are less responsive than their centres, translating into a spaxel active area of approximately 8"x8" where the response is flat. This effect is more severe at shorter wavelengths, and affects (very) extended emission, as well as off-centred point sources and any source that has a size between a point and a very extended. All Level 2/2.5 cubes for these types of sources will be affected, whether pointed or mapping.
    Hence, for centred point source extracted with the task extractCentralSpectrum, no change to the spectra are expected in this version of HIPE because of this effect. For very extended sources, we have developed a new Extended Source Correction calibration file (ExtendedSourceLoss, applied in the pipeline tasks specRespCal and specRespCalToTelescope), and this incorporates the necessary correction as part of the spatial flatfielding for the PACS spectrometer. For these sources, the fluxes of the spectra will differ to what was obtained in previous versions of HIPE. For intermediate sources, a more complex analysis is necessary to estimate the flux loss, and a task to do this will be provided in HIPE 15.
    The fluxes of the spaxels of all cubes will be changed by ~+30% in the blue to ~-5% in the red. The calibration file can be inspected to extract the curve:
    w = calTree.spectrometer.extendedSourceLoss["wavelength"].data
    f = calTree.spectrometer.extendedSourceLoss["fraction"].data
    p=PlotXY(w, 1./f)
    After such a correction, a source of flat surface brightness within the field of view of a single pointing will be well calibrated at the level of the rebinned cubes (i.e. level2). The flux loss between the detectors was already accounted for in the point-source calibration correction in the correspondent calibration file, therefore, point-source calibrated spectra of centred point sources are not affected. For this reason, in HIPE 14, the extractCentralSpectrum task checks and removes the extendedSourceLoss correction from the level2 cubes, in case it has been applied, before extracting the final point source corrected spectrum. However, if working with off-centred point sources and using the tasks extractSpaxelSpectrum and pointSourceLossCorrection, this correction is not taken out, and hence the results will be incorrect. An extra task/function is necessary: this task can be found in the "Point source loss correction (any spaxel)" script in the Scripts->PACS useful menu.
 
  • New beam calibration files have been delivered, differing from the previous files only in the way they are normalised. These will be used in a new task being developed in HIPE 15, and do not impact on HIPE 14 or SPG 14 in any way.
    • all the 25 beams were divided by the peak value of the central spaxel beam;
    • then, they are multiplied to match the Point Source Correction calibration file (pointSourceLoss FM_4).
 
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