An exquisite Point Spread Function (PSF) determination for the Euclid mission is crutial. One of the factor hampering the reconstruction is the presence of multiple stars in the star field. We propose a tool to identify those binaries based on the repeated measurements of the light profile.
Measuring weak gravitation lensing signal to the level required by next generation of space-based surveys demands exquisite point spread function (PSF) reconstruction. However, the presence of unresolved binary stars can significantly distort the PSF shape. In an effort to mitigate this bias, we aim at detecting unresolved binaries in realistic Euclid stellar populations. 7 We tests out methods in numerical experiments where (i) the PSF shape is known to Euclid requirements across the field of view and (ii) the PSF shape is unknown. We draw simulated observations of PSF shapes for this proof-of-concept paper. As per Euclid survey plan, the objects are observed four times. We propose three methods to detect unresolved binary stars. The detection is based on the systematic and correlated biases between exposures of the same object. One method is a simple correlation analysis while the two others use supervised machine learning algorithms (random forest and artificial neural network). In both experiments, we demonstrate the capacity of our methods to detect unresolved binary stars on simulated measurements. The performance depends on the level of prior knowledge of the PSF shape. Good detection performances are observed in both experiments. Full complexity of the images and the survey design are not included, but key aspects of a more mature pipeline are discussed. Finding unresolved binaries in the objects used for PSF reconstruction increases the quality of the PSF determination at arbitrary positions. We show, using different approaches, the capacity of detecting at least the most damaging binary stars for the PSF reconstruction process.
Key words. Methods: data analysis – Methods: statistical – (Stars:) binaries (including multiple): close
The scripts that were used to generate the results of the paper are in the script/ repository. The simulated PSFs are internal to the Euclid Consoritum.
To discover other codes from the astrophysics laboratory of EPFL, you can go there