Up to 100,000 reliable strong gravitational lenses in future dark energy experiments

TL;DR

This paper proposes a new method for reliably identifying up to 100,000 strong gravitational lenses in future dark energy surveys like Euclid and SKA, based on magnification bias, ensuring high reliability and known redshifts.

Contribution

It introduces an alternative selection technique exploiting magnification bias, enabling the detection of a large, reliable sample of gravitational lenses with known redshifts in upcoming surveys.

Findings

Approximately 1,000 lenses detectable in Euclid with high reliability.

Potential to identify up to 100,000 lenses with SKA.

Method provides redshift information and is independent of lens morphology assumptions.

Abstract

The Euclid space telescope will observe ~10^5 strong galaxy-galaxy gravitational lens events in its wide field imaging survey over around half the sky, but identifying the gravitational lenses from their observed morphologies requires solving the difficult problem of reliably separating the lensed sources from contaminant populations, such as tidal tails, as well as presenting challenges for spectroscopic follow-up redshift campaigns. Here I present alternative selection techniques for strong gravitational lenses in both Euclid and the Square Kilometer Array, exploiting the strong magnification bias present in the steep end of the Halpha luminosity function and HI mass function. Around 10^3 strong lensing events are detectable with this method in the Euclid wide survey. While only ~1% of the total haul of Euclid lenses, this sample has ~100% reliability, known source redshifts, high signal-to-noise and a magnification-based selection independent of assumptions of lens morphology. With the proposed Square Kilometer Array dark energy survey, the numbers of reliable strong gravitational lenses with source redshifts can reach 10^5.