Characterize persistence behavior of saturated and non-saturated stellar sources

Characterize the persistence behavior of saturated and non-saturated stellar sources in Euclid NISP detectors, including the distinct temporal evolution of their persistence signals.

Background

The paper models stellar persistence using a simplified prescription based primarily on the central-pixel electron count. For non-saturated sources, the initial signal is set to the expected electron count, whereas for saturated sources the authors impose a conservative fixed value proportional to the detector full-well capacity.

The authors explicitly note that saturated and non-saturated sources are expected to exhibit different persistence behavior, but the treatment of this distinction is not resolved in the analysis. A more accurate characterization is important because saturated bright stars may generate persistence signals with different amplitudes and decay times, affecting predictions of contamination in spectroscopic galaxy catalogues.

References

This is a simplified treatment, as saturated and non-saturated sources are expected to follow different persistence behaviours, whose modelling remains uncertain (Euclid Collaboration: Kubik et al., in prep.).

— Euclid. A two-point correlation approach to diagnosing star-related systematics in the Euclid spectroscopic survey  (2609.05155 - Collaboration et al., 4 Sep 2026) in Appendix, Section "Modelling the stellar images and treatment of saturated stars" (Appendix I0modelling)

Nevertheless, an unknown fraction of residual persistence signals may survive these cuts, depending on the catalogue selection criteria.

— Euclid. A two-point correlation approach to diagnosing star-related systematics in the Euclid spectroscopic survey  (2609.05155 - Collaboration et al., 4 Sep 2026) in Appendix, Section "Tests on Flagship" (Section FS2)