Characterize dual-grism confirmation rate at fainter flux levels

Determine the dual-grism cross-orientation confirmation rate as a function of source flux or signal-to-noise for Euclid NISP SIR slitless spectra of Euclid Q1 galaxy-scale strong-lens candidates, particularly at fainter flux levels than those with SNR greater than 170, to assess performance relevant to the Euclid wide survey.

Background

In the Q1 sample, 393 lenses had spectra in both anti-parallel RGS000 and RGS180 grism orientations, and 369 (94%) showed consistent features in both, providing a high internal confirmation rate.

However, all confirmed cases have high signal-to-noise (SNR > 170), leaving the behavior of the dual-grism confirmation rate at lower SNR unexplored, which is particularly relevant for the larger and deeper Euclid wide survey.

References

Since all confirmed sources in this sample have SNR > 170, the confirmation rate at fainter flux levels—relevant for the Euclid wide survey—remains to be characterized.

— Spectroscopic Redshifts for 461 Euclid Q1 Strong Gravitational Lenses from NISP Slitless Spectroscopy  (2604.02726 - Tata, 3 Apr 2026) in Section 3.6 (Dual-grism confirmation)