WP3: Development and testing of algorithms



Develop and test the algorithms for image detection, de-confusion and photometry in deep and crowded extragalactic fields. These algorithms will be adopted to process the data in WP4.


Description of work

  1. Tune and test the algorithms for object detection. In the optical, SExtractor is not capable of correct and consistent detection of objects over a wide flux range. It must also be modified to work on large mosaics at the CANDELS/EUCLID-Deep scale. A related issue is the estimate of completeness in the detection of galaxies in mid-IR images that have a much broader PSF than the optical and near-IR images. We will use simulations to estimate the completeness in prior-based photometry in mid-IR images. These activities will be executed at INAF and CEA.
  2. Developing and testing of PSF-matching methods. We will test and further develop the available software for PSF-matched photometry, named TFIT and CONVPHOT. These will be applied to images with PSF FWHM ranging from sub-arcsec (WFC3, VLT) to ~2-3 arcsec (optical, Spitzer). We will test whether it is possible to jump from WFC3-like resolution to the significantly poorer-resolution Herschel images. If this does not prove viable, we will tackle separately the problem of prior-based photometry working from Spitzer to Herschel and SCUBA2. This activity will be executed at INAF, UEDIN and CEA.
  3. We will explore and test other techniques for multi-band photometry: matched aperture photometry, cross correlation etc. This will include the optimal measurement of X-ray flux densities for objects detected in other bands. This activity will be executed at INAF, UEDIN, CEA and CDS.
  4. This WP is devoted to cross-checking and comparing the various methods, with the minimum goal of understanding and quantifying the differences, in order to fully characterize the different systematics and define the final recipes to adopt. This activity will be executed in all nodes.
  5. This WP will be devoted to properly coding the public software that will be eventually released, based on the recipes found in the previous WP. In particular we plan to develop and release a new version of a PSF-matching code, resulting from the combined evolution of CONVPHOT and TFIT. This WP will build on the experience and results of the previous ones: for this reason it will start later (Y3). This activity will be executed at INAF.
  6. Spectroscopy of Grism-WFC3 data. A subset of the data we are dealing with are slit-less spectroscopic observations with WFC3 on HST. We will develop here the basic reduction procedures and study the problem of association with deep imaging data. This activity will be executed at UEDIN including external consultants from STScI.