Galaxy–Little Red Dot Strong Lenses: A Missing Population?

Abstract The physical nature of Little Red Dots (LRDs) remains uncertain, although these abundant, compact, and red sources may offer important insights into early black hole growth and galaxy formation. Strong gravitational lensing can magnify LRDs and spatially resolve their internal structure, thereby helping to discriminate among competing physical scenarios. However, no galaxy-scale strongly lensed LRD has yet been securely confirmed. To predict the abundance of such systems in current and future surveys and to guide dedicated searches, we present the first benchmark estimate of the detectable population of galaxy-scale lensed LRDs by combining literature-based LRD source models with a population of foreground early-type-galaxy deflectors. Our Monte Carlo simulation spans 50 deg 2 and contains 270,713 LRDs and 5,460,841 deflectors. We predict idealized surface densities of 10.70 ± 3.76 deg −2 for doubles and 0.64 ± 0.69 deg −2 for quads. After accounting for the JWST point-spread function and survey limiting magnitudes, the detectable surface densities decrease to 3.70 ± 1.89 and 0.52 ± 0.58 deg −2 , respectively. For the deduplicated 0.66 deg 2 footprint covered by COSMOS-Web, PRIMER-UDS, PRIMER-COSMOS, CEERS, JADES GOODS-S, and JADES GOODS-N, for which the reported limiting depths are combined through area-weighted averaging in flux space, the predicted probabilities of detecting no systems are 8.6% for doubles and 70.8% for quads.