A plethora of active galactic nuclei among Lyα galaxies at low redshift

We investigate the fraction of z ∼ 0.3 Lyα emitting galaxies (LAEs), which host active galactic nucleus (AGN) activity, which is typically from 1% to 5% at 2 ≲z≲ 6. Using optical spectroscopy of 23 LAEs at 0.2 ≤z≤ 0.45 selected with Galaxy Evolution Explorer (GALEX) UV data, we probe for AGNs with a variety of methods, including line widths, diagnostic line ratios, high-ionization emission, infrared activity, and X-ray luminosity. We found that our sample of low-redshift LAEs has an AGN fraction of 43 ⁺¹⁸ _-26%, significantly higher than at high redshift. While previous results have shown that low-redshift LAEs have a lower space density than their high-redshift analogs, these results show that star-forming LAEs at low redshift are rarer still. Accounting for differences in available AGN classification methods, we conclude that rest-frame optical spectroscopy is necessary to identify low-luminosity AGNs in LAEs at high redshift, and that limits on the X-ray flux are necessary to determine the extent to which the AGN contaminates the Lyα fluxes.