2009/06/30 by Steven L. Finkelstein, Seth H. Cohen, Sangeeta Malhotra +5 · 2 citations
Physics and Astronomy · #Active galactic nucleus #Astronomy #Astrophysics #Astrophysics and Star Formation Studies #Galaxies: Formation, Evolution, Phenomena #Galaxy #Gamma-ray bursts and supernovae #Luminosity #Physics #Redshift #astro-ph.CO
paper · pdf · doi:10.1088/0004-637x/703/2/l162
published as Astrophys.J.703:L162-L166,2009 · Replaced with ApJL accepted version, 5 pages, 2 figures
arxiv created 2009/08/26 · openalex publication_date 2009/09/16 · arxiv updated 2009/12/01 · openalex created_date 2016/06/24 · openalex updated_date 2026/08/05
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.