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

Steven L. Finkelstein, Seth H. Cohen, Sangeeta Malhotra, James E. Rhoads, Casey Papovich, Zhenya Zheng, Jun Xian Wang

Research output: Contribution to journalArticlepeer-review

23 Scopus citations

Abstract

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.

Original languageEnglish (US)
Pages (from-to)L162-L166
JournalAstrophysical Journal
Volume703
Issue number2 PART 2
DOIs
StatePublished - 2009

Keywords

  • Galaxies: active
  • Galaxies: evolution

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science

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