We investigate the fraction of z ~ 0.3 Lyman alpha emitting galaxies (LAEs) which host active galactic nucleus activity, which is typically from 1 - 5% at 2 < z < 6. Using optical spectroscopy of 23 LAEs at 0.2 < z < 0.45 selected with GALEX UV data, we probe for AGN 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 Lyman alpha fluxes.
@article{arxiv.0906.4554,
title = {A Plethora of AGN Among Lyman Alpha Galaxies at Low Redshift},
author = {Steven L. Finkelstein and Seth H. Cohen and Sangeeta Malhotra and James E. Rhoads and Casey Papovich and Zhenya Zheng and Junxian Wang},
journal= {arXiv preprint arXiv:0906.4554},
year = {2009}
}
Comments
Replaced with ApJL accepted version, 5 pages, 2 figures