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How can I reduce SPIRE FTS spectra for objects that are neither points sources, nor fully extended?
Posted by Mark Kidger on 11 September 2018 12:40 PM
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Reduction and analysis of SPIRE FTS spectra treats two, generic cases: point sources (sources smaller than 3-4 arcseconds that are effectively a point-source for SPIRE) and extended sources (anything larger than 40 arcseconds). However, there are many sources between these two extremes that can neither be treated as point sources, nor as extended. The immediate consequence for observers is that neither the point source reduction, nor the extended source reduction give a good result: users will see this in the form of a large discontinuity between the two SPIRE spectra ranges. There is a Herschel Science Centre short videotutorial that shows you how to categorise sources by diameter and how to identify cases in which neither the point source calibration, nor the extended source calibration give a satisfactory result and how to treat these cases. You can find it here: https://www.youtube.com/watch?v=mxZpHgHVtP4 The short videotutorial will walk you through the basics of SPIRE FTS spectra data reduction, including the need to carry out certain, basic pre-reduction such as to subtract the background first before applying the Semi-Extended Calibration Tool (SECT) to the spectra. It will show you how to set the parameters and, through a practical example, how to make an iterative fit to the effective source diameter. Finally, it will show you the checks that you can carry out to ensure a self-consistent result. | |
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