Identifying Lyman Alpha Emitters powered by AGNs

TL;DR

This paper develops a method to identify high-redshift Lyman Alpha Emitters powered by obscured AGNs using their spectral line skewness and surface brightness profiles, distinguishing them from starburst LAEs.

Contribution

It introduces a novel observational criterion based on radiative transfer simulations to detect AGN-powered LAEs at high redshift.

Findings

Negative line weighted skewness (S_w < 0) indicates AGN presence.

Surface brightness FWHM >= 1.5" is characteristic of AGN-powered LAEs.

The criteria effectively differentiate AGN-powered LAEs from starburst LAEs.

Abstract

Lyman Alpha Emitters (LAEs) are usually thought to be powered by star formation. It has been recently reported that a fraction of LAEs at redshift z~3-4 hosts an Active Galactic Nuclei (AGN). If an AGN is present it could be obscured and undetectable in X-rays, but yet dominate the Lya luminosity. We examine the properties of these AGN-powered LAEs at high redshift (z>=6) using radiative transfer cosmological simulations and obtain a reliable criterion to identify them from their observed \Lya line and surface brightness. We find that these sources should have: (a) negative line weighted skewness, S_w <0, and (b) surface brightness profiles FWHM >= 1.5". This parameter space cannot be populated by starburst LAEs. Thus, LAEs satisfying this criterion would be strong candidates for the presence of a hidden AGN powering their luminosity.