# Finding bright $z \geq 6.6$ Lyman-$\alpha$ emitters with lensing: prospects for Euclid

## TL;DR

This study models the detection of lensed high-redshift Ly$ ext{α}$ emitters with Euclid, predicting their numbers and addressing contamination issues, to enhance understanding of early universe galaxy formation.

## Contribution

It provides the first detailed predictions for detecting lensed Ly$ ext{α}$ emitters at $z ext{≥} 6.6$ with Euclid, incorporating multiple luminosity and lensing models.

## Key findings

- Euclid can detect approximately 0.85 to 1.82 lensed Ly$ ext{α}$ emitters per square degree at $z ext{≥} 6.6$.
- Combining Euclid and SKA will enable identification of 34 to 73 lensed Ly$ ext{α}$ emitters at high redshift.
- Contaminants like [OII], [OIII], H$eta$, and H$ ext{α}$ can be distinguished using spectral resolution and radio observations.

## Abstract

We model the $z \geq 6.6$ Ly$\alpha$ luminosity function to estimate the number of lensed high$-z$ Ly$\alpha$ emitters that may be detected by the Euclid Deep Survey. To span the whole range of possible predictions we exploit two Ly$\alpha$ luminosity function models and two strong gravitational lensing models from the literature. We show that the planned Euclid Deep Survey observing 40 deg$^2$ over the 920-1850 nm wavelength range down to a flux limit of $F_{lim}=5\times10^{-17}\,$erg s$^{-1}\,$cm$^{-2}$ will enable us to find between $\sim 0.85$ and $\sim 1.82$ deg$^{-2}$ lensed Ly$\alpha$ emitters at $z \geq 6.6$ depending on the adopted Ly$\alpha$ luminosity function and strong gravitational lensing model. The obvious [OII], [OIII] and H$\beta$ contaminants of the Ly$\alpha$ lensed population will be identified with the help of Euclid's spectral resolving power, while the SKA will enable the identification of the interloper population of H$\alpha$ emitters. By combining Euclid and the SKA, we will thus be able to identify, for the first time, a sample of $\sim 34$ to $\sim 73$ lensed Ly$\alpha$ emitters at $z \geq 6.6$.