Quantify the residual false-positive rate in NISP slitless spectroscopy

Quantify the residual false-positive rate for spectral feature detections and redshift identifications in Euclid NISP SIR slitless spectroscopy of the Euclid Q1 strong gravitational lens sample by performing injection–recovery tests on blank sky regions, in order to assess contamination from overlapping spectra and detector artifacts after dual-grism verification.

Background

Slitless spectroscopy is vulnerable to contamination from overlapping spectra of neighboring objects, and the study uses anti-parallel grism orientations to mitigate this via cross-correlation.

Despite this mitigation, the residual false-positive rate has not been measured and requires dedicated injection–recovery testing on blank sky regions to establish the reliability of detections; the authors defer this quantification to future work.