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Deep imaging of the diffuse light emitted by the stellar fine structures andouter halos around galaxies is now often used to probe their past massassembly. Because the extended halos survive longer than the relatively fragiletidal features, they trace more ancient mergers. We use images reaching surfacebrightness limits as low as 28.5-29 mag.arcsec-2 (g-band) to obtain light andcolor profiles up to 5-10 effective radii of a sample of nearby early-typegalaxies. They were acquired with MegaCam as part of the CFHT MATLAS largeprogramme. These profiles may be compared to those produced by simulations ofgalaxy formation and evolution, once corrected for instrumental effects. Indeedthey can be heavily contaminated by the scattered light caused by internalreflections within the instrument. In particular, the nucleus of galaxiesgenerates artificial flux in the outer halo, which has to be preciselysubtracted. We present a deconvolution technique to remove the artificial halosthat makes use of very large kernels. The technique based on PyOperators ismore time efficient than the model-convolution methods also used for thatpurpose. This is especially the case for galaxies with complex structures thatare hard to model. Having a good knowledge of the Point Spread Function (PSF),including its outer wings, is critical for the method. A database of MegaCamPSF models corresponding to different seeing conditions and bands was generateddirectly from the deep images. It is shown that the difference in the PSFs indifferent bands causes artificial changes in the color profiles, in particulara reddening of the outskirts of galaxies having a bright nucleus. The method isvalidated with a set of simulated images and applied to three representativetest cases: NGC 3599, NGC 3489, and NGC 4274, and exhibiting for two of them aprominent ghost halo. The method successfully removes it.

A Deconvolution Technique to Correct Deep Images of Galaxies from Instrumental Scattered Light