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Why do I get strange SPIRE photometry for a source in a high background region?
Posted by Mark Kidger, Last modified by Mark Kidger on 04 July 2018 01:56 PM

Answer supplied by Ivan Valtchanov:

 

When carrying out photometry the background estimation is critical. PSF fitting tasks, such as sourceExtractorSussextractor, do not give the best results when the background is highly structured. Some of the source extraction tools implement background estimation and the results with and without should be compared.

In most cases, the preferred approach is to use aperture photometry, with background taken from an adjacent annulus or taken from a pre-selected region near the source. This is an interactive, manual method and is convenient for a small number of sources.

You can find out more about background estimation and its effect on SPIRE photometry in two, useful Herschel Science Centre short videotutorial presentations:

SPIRE Photometer: photometry of point sources - https://www.youtube.com/watch?v=nbN6OWtWIR0

SPIRE Photometer: aperture photometry - https://www.youtube.com/watch?v=fjzf-VN_X0s

 

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