18 October 2012, 15:00 CEST
Chair: Luca Conversi (HSC)

in the call: Luca Conversi, Javier Diaz, Chris Pearson, Drew, Jean Matagne, Peter Barnes, Stephan Ott, Wanggi, , Call-in user1, Maria Khramtsova,, Veli-Matti Pelkonen, Bruno MerĂ­n

Presentation




- Presentation from the HIPE Forum 2012 on SPIRE photometry
- The time-line fitter works better for small maps and you get errors down to 2-5 % on flux over the typical 10 %.
- Other methods are: SEXtractor and star-finder.
- SEXtractor works in maps in Jy/pixel, so you need to divide the beam area to use it and there is a variation of 10% on this change, which adds to the final error. For that reason, if you are after very low error in your photometry it is much better to stay in HIPE.
- In HIPE 9, the parallel and small map pipelines are identical.
- The destriper creates a Diagnostic table, which lists the number of iterations that destriper needed to converge to a final chiSquared, a_0 is the parameter that was fitted. The default is to use median fitting.
- Dividing the SPG < 8.x images with that from HIPE 9 (using the destriper) you see the low-intensity stripes that were removed from the images (with amplitudes of -6 to 4 mJy).

SPIR photometry demo script




- Photometry demo
- the level1 context has the DC level still, so we need to reprocess everything with the destriper.
- The errors should be smaller after you have used the destriper. All photometry of galactic fields from pre-9 HIPE versions should be rechecked with HIPE 9+ because there fluxes could have changed beyond the 10 % nominal errors. However, if you used scanamorphos then you would be in a good shape because in principle scanamorphos images are essentially the same as destriper ones.
- The destriper removes the DC component.
- the detThreshold variable has different meanings in the suss extractor and in the Daophot
- Spire maps continue to be in Jy/beam
- A new nice feature we added to Daophot this time was to add the doApertureCorrections, which applies the corrections to the apertures and is activated by default.
- DaoPhot identified more sources and the fluxes are slightly lower in DaoPhot than in suss extractor, even after the aperture corrections have been applied. The differences are even larger if you don't apply the aperture corrections.
- DaoPhot is underestimating the source fluxes compared to suss extractor.
- The time-line fitter does not extract sources, but needs a sourceList.
- For time-line fitting, Rpeak needs to be set to 22, 33 and 42 arc sec, which are the radius where to look for the peaks.
- the inputs to the time-line fitting (sourceExtractorTimeline) is the destripped scans, the coordinates, which can be either a sourceList product, a list of manually-created world coordinates or any other combination.
- the errors that the source extractors in HIPE are statistical, so one needs to add the 7% which is the absolute flux calibration.
- Recommended apertures for PSW are 22, 60 and 90 arc sec. In the SPIRE Data Reduction Guide.
- the annular sky aperture photometry estimates 205 mJy before aperture correction (261 mJy from time-line fitting)
- After the aperture correction, the computed flux for the brightest source (gamma Dra) is 260.39 mJy.
- The error from the aperture correction is also not correct for SPIRE maps. In order to calculate the

errors from a point source, one should integrate the error map in that area.
- proposal to have another webinar on scanamorphos. For SPIRE destriper is providing very similar results as scanamorphos so it does not make a big difference for SPIRE.

Questions and Answers

    • Questions:
    • (?) Are you going to make a webinar about scanamorphos?
      • A: It is currently not considered but we might consult with Helene Roussel about this and inform users accordingly.

Webinar contents

  • Short presentation on new improvements of SPIRE pipeline in HIPE 9
  • Presentation on how to do photometry with SPIRE using HIPE
  • Hands-on session, part 1: data reduction of small-map observation
  • Hands-on session, part 2: point source extraction in HIPE with timeline fitter, Sussex/DAOphot extractors and aperture photometry
  • AOB

Note: for the hands-on demo, it will be used the GammaDra calibration observation having obs. ID 1342195871
If users have any other wish or issues with specific observation, please advice before the webinar so that they can be investigated.